Medical glossary

The contribution of abdominal fat to body shape

A Body Shape Index is a measure that isolates the contribution of waist circumference (abdominal fat) to body shape, adjusted for height and BMI. A high ABSI is linked to greater health risk independently of weight. The result is interpreted as a z-score relative to people of the same sex and age.

A liver enzyme; a marker of liver-cell damage

ALT (alanine aminotransferase) is an enzyme located mainly inside liver cells. When they are damaged, ALT leaks into the blood, so its rise is a sensitive sign of liver problems (fatty liver, hepatitis, the effects of alcohol and medications).

The cellular "energy sensor" that switches on when energy is scarce

AMPK (AMP-activated protein kinase) is an enzyme that is activated when the cell's energy store falls (fasting, exertion) and shifts metabolism into an economy mode: it enhances autophagy and fat burning and suppresses mTOR. It is considered one of the key mediators of the beneficial effects of fasting and physical activity.

Atherosclerotic Cardiovascular Disease — the group of conditions caused by atherosclerosis: heart attack, stroke, coronary heart disease.

ASCVD includes: non-fatal myocardial infarction, death from coronary heart disease, and non-fatal or fatal stroke. The Pooled Cohort Equations (ACC/AHA, 2013) estimate the 10-year risk of a first ASCVD event in people without existing cardiovascular disease. At a risk of ≥7.5%, a discussion of statin therapy is recommended. The equations were derived from data on more than 500,000 participants in the NHLBI cohort studies.

An enzyme of the liver, heart and muscles; a marker of tissue damage

AST (aspartate aminotransferase) is an enzyme found in the liver, heart and muscles. It is less specific to the liver than ALT. The AST/ALT ratio (the De Ritis ratio) helps distinguish the causes of damage; AST is a component of the FIB-4 fibrosis index.

Excess fat in the abdominal area

Abdominal (central) obesity is the predominant accumulation of fat around the waist and internal organs. It is defined by waist circumference independently of BMI and is closely linked to metabolic syndrome and cardiovascular risk.

Dark, velvety patches of skin — a marker of insulin resistance

Acanthosis nigricans is darkened, velvety-to-the-touch patches of skin on the neck, armpits and groin. It is a common skin sign of insulin resistance and metabolic syndrome.

How many times the pace of aging differs from normal

A measure from the Gorelkin–Pinkhasov method: the ratio of the body's actual age-related "wear" to the norm. Values of 0.95–1.05 are a physiological pace; below 0.95 is slowed aging; above 1.05 is accelerated. It is calculated from the waist-to-hip ratio and the body mass index, adjusted for age and sex.

The main plasma protein — a marker of protein status and liver function

Albumin is the most abundant plasma protein (60% of total protein) and is synthesized in the liver. It maintains the blood's oncotic pressure and transports drugs, hormones and fatty acids. Normal range: 35–52 g/L. It falls with liver disease, malnutrition, nephrotic syndrome and chronic inflammation. A drop in albumin is one of the strongest predictors of mortality in older people and enters the PhenoAge and Bortz Blood Age formulas with a negative coefficient (higher albumin — a younger biological age).

The appearance of albumin protein in the urine — an early sign of glomerular damage that precedes overt kidney failure.

Normal range: <30 mg/g creatinine. Microalbuminuria (30–300 mg/g) is detected in diabetes and hypertension long before GFR declines. It is a marker of endothelial dysfunction and increased cardiovascular risk.

Liver damage due to alcohol consumption

Alcoholic Liver Disease (ALD) is a spectrum of liver damage caused by alcohol consumption: from fatty liver to alcoholic hepatitis and cirrhosis. The ANI index helps distinguish it from non-alcoholic fatty liver disease by blood tests, especially when the alcohol history is unreliable.

an enzyme of the bile ducts and bones, a marker of cholestasis

Alkaline phosphatase (ALP) is an enzyme that in the liver is located in the epithelium of the bile ducts; it is also present in bone, intestine and placenta. It rises when bile outflow is impaired (cholestasis). In the R-factor the multiple of ALP above the upper limit of normal is used; its predominance shifts the result toward a cholestatic pattern. With an isolated rise, the source is clarified by GGT.

The accumulated wear on the body from chronic stress

Allostatic load is the cumulative biological "wear and tear" accrued during prolonged adaptation to stress. When the body mobilizes the stress response again and again (raising cortisol, blood pressure and inflammatory markers), that activation comes at the cost of accelerated aging of organs and systems. A high allostatic load is associated with accelerated epigenetic aging (GrimAge) and with the risk of cardiovascular disease, dementia and metabolic disorders. It includes 10+ biomarkers: cortisol, IL-6, CRP, blood pressure, BMI, HbA1c.

A neurodegenerative disease — the most common cause of dementia.

Alzheimer's disease is a progressive neurodegenerative disorder characterized by the accumulation of β-amyloid plaques and tau-protein neurofibrillary tangles in the brain. It accounts for 60–70% of all dementia cases. Main symptoms: progressive amnesia, speech impairment, disorientation and personality changes. Early biomarkers: β-amyloid 42 and phospho-tau in cerebrospinal fluid or on PET. Elevated homocysteine (>14 µmol/L) nearly doubles the risk of the disease (Framingham Study, NEJM 2002).

The building blocks of the body's proteins

Organic compounds that are the structural elements of proteins. There are 20 standard amino acids, 9 of which are essential (not synthesized by the body). They participate in the synthesis of hormones, neurotransmitters and immune proteins. Analysis of the amino-acid profile reveals metabolic disorders.

A pathological protein that accumulates in the brain in Alzheimer's disease

β-amyloid (Aβ) is a fragment of the APP protein that is normally cleaved, but in Alzheimer's disease it forms insoluble aggregates — "plaques" between neurons. The accumulation of amyloid plaques triggers inflammation, disrupts synaptic transmission and ultimately leads to neuronal death. The amyloid hypothesis is the leading concept of Alzheimer's pathogenesis. Amyloid levels can be measured by PET scanning or cerebrospinal-fluid analysis.

Fat predominantly on the abdomen

A fat-distribution pattern dominated by deposits around the waist and abdomen (the "apple" shape). It is associated with the accumulation of visceral fat around the organs and with an increased risk of metabolic syndrome, cardiovascular disease and type 2 diabetes. It is more common in men and is reflected in a high WHR.

A drop in hemoglobin below the normal level

Anemia is a reduced hemoglobin concentration: in women <12 g/dL, in men <13 g/dL (WHO). The most common cause is iron deficiency (iron-deficiency anemia). Other causes: B12/folate deficiency, chronic disease, hemolysis and blood loss. Symptoms: weakness, shortness of breath, pallor and tachycardia. Grades: mild (Hb 10–12/13), moderate (8–10), severe (<8 g/dL).

Drugs that reduce stomach acidity

Antacids and proton-pump inhibitors (omeprazole, pantoprazole) reduce the acidity of gastric juice. Hydrochloric acid is needed to reduce Fe³⁺ → Fe²⁺ and to absorb iron in the duodenum. Long-term use of acid-suppressing drugs lowers iron absorption by 40–70%.

A marker of autoimmune thyroiditis

Antibodies to thyroid peroxidase — an enzyme involved in the synthesis of thyroid hormones. Their elevation is a key sign of Hashimoto's autoimmune thyroiditis and can appear years before TSH shifts. Even low detectable levels warrant monitoring. Normal range 0–34 IU/mL.

A pathological state of excessive worry

An emotional state characterized by worry, tension and a sense of impending threat. Anxiety correlates with a high PSS score and elevated cortisol. Clinically significant anxiety is diagnosed by the GAD-7, HADS-A and Beck scales.

The main protein of "good" HDL particles; it protects vessels from atherosclerosis

ApoA1 (Apolipoprotein A1) is the main protein component of high-density lipoproteins (HDL), making up 70% of their protein mass. It activates the enzyme LCAT, which carries out reverse cholesterol transport — the removal of cholesterol from vessel walls to the liver. Normal range: men 1.04–2.02 g/L, women 1.08–2.25 g/L. It is a more accurate predictor of cardiovascular risk than HDL cholesterol itself. In the Bortz Blood Age model it enters with a negative coefficient (higher ApoA1 — a younger biological age).

Programmed cell death

Apoptosis is a genetically programmed form of cell death, triggered by critical telomere shortening, irreparable DNA damage or signals from the immune system. Unlike necrosis, apoptosis occurs without inflammation — the cell is neatly disassembled into fragments that macrophages engulf. It serves as a protective mechanism against malignant transformation.

A sustained rise in blood pressure ≥130/80 mmHg — the leading modifiable risk factor for stroke and heart attack.

By the ACC/AHA 2017 classification: normal <120/80, elevated 120–129/<80, stage 1 hypertension 130–139/80–89, stage 2 hypertension ≥140/90. Hypertension damages the vascular endothelium, accelerates atherosclerosis, causes left-ventricular hypertrophy and raises the risk of kidney failure. It is symptomless until complications arise, which is why it is called the "silent killer". Treatment with antihypertensive drugs lowers stroke risk by ~35–40%.

The buildup of cholesterol plaques in artery walls — the main cause of heart attacks and strokes.

A chronic inflammatory disease of the arteries: LDL cholesterol is deposited in the vessel wall, forming an atherosclerotic plaque. The plaque narrows the vessel lumen and can rupture, causing thrombosis. The result is a myocardial infarction or stroke. It develops over decades and shows clinically late. Key risk factors: high LDL, smoking, arterial hypertension and diabetes mellitus.

Chaotic contraction of the atria — the most common arrhythmia

Atrial fibrillation (AF) is a heart-rhythm disorder in which the atria contract chaotically at 350–700 impulses per minute. It raises the risk of stroke fivefold and of heart failure threefold. It is diagnosed by ECG. Prevalence: about 2% of the population, rising sharply after age 65. It is one of the markers of an "old" heart.

The main cause of hypothyroidism in developed countries

Autoimmune thyroiditis (Hashimoto's thyroiditis) is a chronic inflammation in which the immune system gradually destroys the thyroid gland, leading to hypothyroidism. It is confirmed by elevated anti-TPO / anti-TG and often co-occurs with other autoimmune diseases.

The cell's self-cleaning of damaged components

A cellular process of disposing of and recycling damaged organelles and proteins ("self-eating"). It supports cell renewal and is linked to protection against neurodegeneration and aging. It is activated by calorie restriction and intermittent fasting, by exercise and by nutrient scarcity.

A protein that acts as "fertilizer" for neurons and synapses

Brain-Derived Neurotrophic Factor is a protein of the neurotrophin family that supports neuron survival, synapse growth and neuroplasticity. It acts as "fertilizer" for nerve cells. BDNF levels rise with aerobic exercise, learning and good-quality sleep, and are associated with better memory and a lower risk of neurodegeneration.

Body mass index

BMI = body weight (kg) / height² (m). Normal: 18.5–24.9. Overweight: 25–29.9. Class I obesity: 30–34.9. Class II obesity: 35–39.9. Class III obesity: ≥40. It does not account for the ratio of muscle to fat tissue.

The ratio of BMI to the upper limit of normal (24.9)

BMI Prime is the ratio of your BMI to the upper limit of the optimal range (24.9 kg/m²). It is a dimensionless number independent of units: below 1.0 means weight below the upper limit of normal; 1.0 is exactly at the boundary; above 1.0 is overweight (for example, 1.30 = 30% above the optimum). It is convenient for comparison across populations but, like ordinary BMI, does not account for body composition.

The energy the body spends at rest

The basal metabolic rate (BMR) is the amount of energy (kcal/day) the body spends at complete rest on the work of the heart, breathing, maintaining temperature and renewing cells. It depends on sex, age, height and body mass, and accounts for 60–70% of all daily energy expenditure.

A bile pigment; it rises when liver function is impaired

Bilirubin is a yellow-orange pigment, a product of hemoglobin breakdown. The liver captures and neutralizes it; when the liver is damaged or bile outflow is obstructed, total bilirubin in the blood rises. It is included in the FibroTest calculation.

The body's real age, independent of the passport age

Biological age (BA) reflects the body's functional state based on laboratory values, physical parameters and organ condition. It can run ahead of or behind chronological age. The difference between BA and chronological age is a measure of the pace of aging.

A measurable indicator that reflects the body’s biological age

A biomarker of aging is a measurable characteristic that predicts functional status, disease risk or mortality better than chronological age. They may be molecular (DNA methylation, telomeres, blood biochemistry), physiological (blood pressure, ECG age) or functional (grip strength, walking speed). An ideal biomarker is sensitive to interventions, validated, inexpensive and reproducible. Biomarkers are the foundation of evidence-based preventive medicine.

The pressure of blood on the artery walls, given as two values: SBP/DBP

The pressure of circulating blood on the vessel walls. It is expressed as two numbers: systolic (the upper value, at the moment of heart contraction) and diastolic (the lower value, at the moment of relaxation). The reference normal is about 120/80 mmHg. Both values independently affect cardiovascular risk; a rise above 140/90 is called hypertension.

Regions of the world with an abnormally high share of long-lived people

Blue Zones are several regions where, according to researchers' observations, an unusually high proportion of people live to 90–100: Okinawa (Japan), Sardinia (Italy), the Nicoya Peninsula (Costa Rica), Ikaria (Greece) and the Adventist community in Loma Linda (USA). The concept was popularized by Dan Buettner; it is observational in nature and has been criticized for the quality of its underlying age data.

The ratio of fat, muscle and other tissues

Body composition describes what body mass is made of: adipose tissue, muscle (lean mass), bone and water. For health, the proportions matter more than weight itself: adequate muscle mass and a moderate percentage of fat, especially visceral. It is assessed by body-fat percentage, the waist-to-height ratio and lean mass.

The share of body mass made up of fat

The share of total body mass that consists of adipose tissue. Unlike BMI, it reflects body composition — the ratio of fat to lean mass (muscle, bone, organs). It comprises essential fat and stored fat (subcutaneous and visceral). It is estimated by calculation methods (the US Navy method from circumferences, the Deurenberg formula from BMI) or instrumentally (DEXA, bioimpedance).

An extended biological age from 25 biomarkers, trained on UK Biobank

Bortz Blood Age is a biological-age model developed by Jordan Bortz et al. (Communications Biology, 2023) on UK Biobank data (306,116 people). It uses Elastic-Net Cox regression over 25 blood biomarkers plus age and sex. With a C-index of 0.778 (95% CI 0.767–0.788) it outperforms PhenoAge by 11% in relative accuracy of mortality prediction. Biological age is calculated as BA = chronological age + BAA, where BAA (biological age acceleration) is the deviation computed as the sum of centered biomarkers multiplied by the model’s coefficients.

A marker of inflammation in the body

An acute-phase inflammation protein synthesized by the liver. It rises with infections, autoimmune diseases and cancer. Normal range: <5 mg/L. It is a sensitive indicator of an inflammatory process.

Chronic kidney disease — a persistent impairment of kidney function

Chronic kidney disease (CKD) is a persistent (≥ 3 months) impairment of kidney structure or function that is significant for health. It is classified by the glomerular filtration rate (categories C1–C5) and by the level of albuminuria. The lower the eGFR and the higher the albuminuria, the greater the risk of progression and cardiovascular complications.

Cardiovascular disease

A group of diseases of the heart and blood vessels: coronary heart disease, myocardial infarction, stroke, arterial hypertension and heart failure. It is the leading cause of death worldwide. Prevention includes controlling cholesterol, blood pressure and blood sugar.

The main mineral of bones and teeth, regulating neuromuscular transmission, blood clotting and heart rhythm.

When dietary intake is deficient, the body mobilizes calcium from the bones to keep the blood level normal. A serum test may be normal even in osteoporosis. It is assessed together with vitamin D, PTH and ionized calcium.

The volume of blood the heart pumps in one minute

Cardiac output (CO) is the volume of blood ejected by the left ventricle into the aorta in one minute. It is calculated as: CO = stroke volume × heart rate. Normal range: 4.5–8 L/min (at rest). On echocardiography it is denoted LV_CO. It declines with age because of a reduced stroke volume and heart-rate adaptation. In the RGNKTs study (2023) LV_CO was among the top-5 predictors of the heart's biological age on echocardiography.

The ability to sustain aerobic work for a long time

Cardiorespiratory (aerobic) fitness is the ability of the cardiovascular and respiratory systems to supply the muscles with oxygen during prolonged exertion. Its objective measure is VO₂max. High fitness is one of the strongest predictors of health and lifespan; it declines with age and inactivity but rises with regular cardio.

Autoimmune gluten intolerance

Celiac disease is an autoimmune disorder in which eating gluten (a protein of wheat, rye and barley) causes inflammation and atrophy of the villi of the small intestine. It presents with impaired nutrient absorption, diarrhea and deficiencies. It is diagnosed by antibodies and biopsy.

The irreversible arrest of division of an "aged" cell

Cellular senescence is a state of irreversible cell-cycle arrest that arises with critical telomere shortening, DNA damage or oncogenic stress. Senescent cells do not divide but remain metabolically active and secrete pro-inflammatory factors (the SASP phenotype). Their accumulation in tissues accelerates systemic aging and raises the risk of age-related diseases.

the stasis of bile due to impaired outflow

Cholestasis is a disruption of the formation or outflow of bile, in which its components are retained in the liver and blood. In the lab it presents as a predominant rise in alkaline phosphatase (ALP) and GGT, often with bilirubin. With an R-factor <2 the injury is classified as cholestatic. Causes: stones, compression or inflammation of the bile ducts, and certain medications.

A blood fat; a building material for cells and hormones

Cholesterol is a fat-like substance needed for cell membranes and hormones. Total cholesterol is made up of the LDL ("bad") and HDL ("good") fractions. It is not so much the total level that matters as the balance of the fractions — the risk of atherosclerosis depends on it.

Prolonged psychophysiological strain

A state of persistent activation of the stress response (the HPA axis: hypothalamus → pituitary → adrenal glands). Chronic stress raises cortisol, causes systemic inflammation, shortens telomeres and accelerates biological aging. It is associated with depression, anxiety disorders and cardiovascular and autoimmune diseases.

Passport age — the number of years lived

The number of full years that have passed since birth. It serves as a reference point for comparison with biological, metabolic and other functional measures of age. It does not always reflect true health status.

Daily fluctuations of BP: a morning peak, a minimum during sleep

The regular daily fluctuations of blood pressure: a peak in the morning hours (between 6:00 and noon, on the background of the cortisol surge at waking), a decline in the afternoon, a small evening rise and a minimum during sleep. A disruption of this rhythm (for example, the absence of a nocturnal dip) is linked to an increased risk of complications.

The extreme stage of liver fibrosis with irreversible tissue restructuring

Cirrhosis is the final stage of chronic liver disease, in which massive fibrosis and regenerative nodules irreversibly disrupt the organ's structure and function. It raises the risk of liver failure and liver cancer; it corresponds to F4 on METAVIR.

The brain's age from memory, thinking speed and flexibility

An estimated measure reflecting how well the brain's performance (memory, information-processing speed, attention, adaptability) matches the average values of a given age group. Unlike chronological age, cognitive age is malleable: it is influenced by lifestyle, sleep, learning and the regularity of mental exertion. It can be lower than the passport age (a "younger" brain) or higher with cognitive aging.

Age-related changes in memory, thinking speed and concentration — normal, not a disease

A physiological process of the gradual decline of information-processing speed, working memory and cognitive flexibility, linked to changes in the brain. In normal cognitive aging a person retains functional independence. The key distinction from pathology is that the changes do not disrupt daily life. The NIA and WHO distinguish three states: normal aging → MCI → dementia.

The ability to change perspective and strategy in response to new data

The ability to switch between concepts, restructure a strategy and change one's opinion as new information arrives — a component of executive function. High flexibility is linked to easy adaptation to change, while rigidity and reliance on fixed routines reduce it.

The brain's resilience to damage, built through education and intellectual activity

Cognitive reserve is the brain's ability to compensate for damage and age-related changes through the neural connections formed over a lifetime. People with a high cognitive reserve retain function longer even in the presence of pathological changes in the brain. It is built through education, mental work, learning languages, reading and social activity. It is a key modifiable factor protecting against dementia.

The main stress hormone of the adrenal glands

A steroid hormone produced by the adrenal cortex. It regulates the "fight or flight" response, raises glucose levels and suppresses inflammation. Chronically elevated cortisol accelerates aging, weakens immunity and disrupts sleep and memory.

A statistical method for estimating factors of mortality or event risk over time

Cox regression (the Cox proportional hazards model) is a survival-analysis method that estimates the contribution of each factor (biomarker) to the risk of an event (for example, death) over time. It does not require knowing the shape of the time-to-event distribution. It is used to build "biological-age biomarkers": the model’s coefficients show how each biomarker shifts risk, which makes it possible to "translate" biomarkers into years of biological age. It underlies the PhenoAge (Levine 2018) and Bortz Blood Age (2023) models.

A product of muscle metabolism — the main marker of kidney function

Creatinine is a breakdown product of creatine phosphate in the muscles, excreted by glomerular filtration in the kidneys. Normal range: men 60–110 µmol/L, women 50–100 µmol/L. The blood level depends on muscle mass and kidney function. It is used to calculate GFR. It rises with kidney failure and active muscle catabolism. In biological-age models (PhenoAge, Bortz) an elevated creatinine is associated with an older biological age — but it should be interpreted together with cystatin C (muscle mass as a protective factor).

Chronic intestinal inflammation

Crohn's disease is a chronic autoimmune inflammatory disease of the gastrointestinal tract (most often the ileum and colon). The inflamed mucosa poorly absorbs iron and other nutrients. It is one of the key risk factors for iron-deficiency anemia — up to 75% of patients have anemia.

An accurate marker of kidney function, independent of muscle mass

Cystatin C is a low-molecular-weight protein produced by all nucleated cells, filtered in the kidney glomeruli and fully reabsorbed in the tubules. It is independent of muscle mass, age and sex (unlike creatinine) — which is why it is considered a more accurate marker of the glomerular filtration rate. Normal range: 0.5–1.0 mg/L. It rises when kidney function declines, often earlier than creatinine. In the Bortz Blood Age model cystatin C has one of the largest coefficients — it is one of the key markers of biological age.

the destruction of liver cells with release of enzymes into the blood

Cytolysis is the damage and death of hepatocytes (liver cells), in which intracellular enzymes — primarily ALT and AST — leak into the blood and rise on tests. A predominance of ALT over alkaline phosphatase (R-factor >5) indicates a hepatocellular pattern of injury. Causes: viral hepatitis and autoimmune, toxic and drug-induced damage.

A marker of clot formation and clot breakdown

The D-dimer is a fibrin breakdown product formed when clots dissolve. A rise >500 ng/mL indicates active clot formation. It is used to rule out deep vein thrombosis and pulmonary embolism (PE).

An eating pattern to lower blood pressure (vegetables, potassium, whole grains)

Dietary Approaches to Stop Hypertension is an eating pattern designed to lower blood pressure. It is rich in vegetables and fruit (potassium, magnesium), whole grains, lean protein and low-fat dairy, with limited salt, sugar and saturated fat. In trials it lowers systolic blood pressure by 8–14 mmHg.

The reference method for assessing body composition

Dual-energy X-ray absorptiometry is an instrumental method that precisely measures fat mass and lean mass as well as bone mineral density. It is considered one of the reference standards for body-composition assessment, against which body-fat-percentage estimation formulas are compared.

Deoxyribonucleic acid — the carrier of genetic information

DNA (deoxyribonucleic acid) is the molecule that contains the genetic program of the entire organism. It consists of two helically twisted chains of nucleotides. It is located in the nucleus of every cell and encodes the synthesis of all the body's proteins.

Chemical marks on DNA — the molecular "clock" of biological age

DNA methylation is the addition of a methyl group (CH₃) to cytosine bases in DNA. Methylation patterns change predictably with age across the genome, forming a "biomolecular timestamp." This is the basis of epigenetic clocks (Horvath's algorithm and its derivatives). DNA methylation tests read hundreds of markers at once and calculate biological age to within a few years. Unlike the genetic sequence, methylation patterns are dynamic and amenable to lifestyle correction.

DNA methylation age — an estimate from epigenetic clocks

DNAm Age (DNA methylation Age) is biological age estimated from the methylation level of specific CpG sites in DNA. First-generation epigenetic clocks (Horvath 2013, Hannum 2013) are trained to predict chronological age; second-generation clocks (PhenoAge, GrimAge) to predict mortality and health. In the Levine 2018 formula, DNAm Age is estimated from PhenoAge through a two-step transformation, giving an approximate estimate without the need for methylation testing.

An AI method that learns from large data — the basis of ECG analysis

Deep learning is a subfield of machine learning based on multilayer neural networks that mimic the working of the brain's neurons. In medicine it is used to analyze ECG, MRI and CT and to interpret genomic data. AI models trained on hundreds of thousands of ECGs detect patterns of the heart's electrical activity that are invisible to the human eye — including the heart's biological age.

A progressive decline in cognitive function that disrupts daily life.

Dementia is a syndrome in which the decline of memory, thinking, orientation and other cognitive functions is severe enough to disrupt everyday activity. The most common form is Alzheimer's disease (60–70%). Other causes: vascular dementia, dementia with Lewy bodies and frontotemporal dementia. Modifiable risk factors: hypertension, diabetes, obesity, depression, physical inactivity and elevated homocysteine. Global prevalence: more than 55 million people (WHO, 2023).

Measurement of bone mineral density

Dual-energy X-ray absorptiometry (DEXA) is the gold standard for measuring bone mineral density. It uses a low radiation dose and is fast and painless. The result (the T-score) is used to diagnose osteopenia and osteoporosis and to assess fracture risk.

A chronic disorder of glucose metabolism: type 2 is linked to insulin resistance and sharply raises cardiovascular risk.

Diagnostic criteria: fasting glucose ≥7.0 mmol/L, or HbA1c ≥6.5%, or glucose ≥11.1 mmol/L 2 hours after a load. Type 2 diabetes doubles the risk of heart attack and stroke: chronic hyperglycemia damages the endothelium, accelerates atherosclerosis and impairs blood clotting. Under the ACC/AHA guidance, patients with diabetes aged 40–75 with LDL 70–189 mg/dL are candidates for statin therapy.

The heart's ability to relax and fill with blood between contractions

Diastolic function is the ability of the left ventricle to relax and passively fill with blood during the diastolic phase. It is assessed by echocardiography parameters: E/A, DT (deceleration time), e' (tissue Doppler) and E/e'. Impaired diastolic function (diastolic dysfunction) is the earliest and most common manifestation of age-related heart aging. E/A < 1 is the first sign. Progression leads to diastolic heart failure. It responds to correction with regular aerobic exercise.

The lower pressure — at the moment the heart relaxes

The minimum pressure in the arteries during the heart's relaxation (diastole), when the heart "rests" between beats. It reflects the tension and elasticity of the vessel wall. The normal range is 60–80 mmHg. A DBP that is too low (<70) in older people and with stiff vessels worsens the prognosis because of reduced blood supply to the myocardium.

liver damage caused by drugs, supplements or toxins

Drug-Induced Liver Injury (DILI) is liver damage provoked by taking medications, herbal remedies, supplements or toxins. It may follow a hepatocellular, cholestatic or mixed pattern; the pattern is determined by the R-factor (the ratio of ALT to alkaline phosphatase). The diagnosis is one of exclusion, made by a doctor based on the totality of the data.

A working-memory trainer with a visual and an auditory stream

A training task in which you track a visual position and a sound at the same time and flag when either matches what appeared N steps earlier. It is one of the few training regimes for which studies have shown transfer to working memory and fluid intelligence, rather than improvement on the game alone.

An epigenetic measure of the pace of aging: how many biological years the body ages per calendar year

DunedinPACE (Pace of Aging Computed from the Epigenome) is an epigenetic biomarker developed at the University of Dunedin. Unlike classic epigenetic clocks, it measures not age but the pace of aging: a value >1.0 means the body ages faster than one year per year. It was trained on 19 biomarkers of physiological aging tracked from birth. It is sensitive to lifestyle changes over a few months, which makes it well-suited to evaluating interventions.

The ratio of early to late filling velocities of the left ventricle

E/A is the ratio of peak transmitral flow velocities in diastole: E (early) is the early phase of passive filling, and A (atrial) is the late phase produced by atrial contraction. In young people the normal value is E/A > 1. With age the myocardium loses elasticity, the early phase weakens, and E/A falls below 1 (pseudonormalization → restrictive pattern). E/A showed the strongest correlation with age (|ρ| ≈ 0.88) among all echocardiography parameters in the RGNKTs study (2023). It is a key marker of the heart's diastolic function.

A recording of the heart's electrical activity

Electrocardiography (ECG) is a diagnostic method that records the heart's electrical activity using electrodes placed on the skin. A standard 12-lead ECG takes less than a minute and can detect arrhythmias, signs of a heart attack and conduction disturbances and assess heart function overall. AI algorithms trained on hundreds of thousands of ECGs extract information about the heart's biological age from it.

A heart ultrasound — an ultrasound study of the heart's structure and function

Echocardiography is an ultrasound diagnostic method that allows real-time assessment of the heart's morphology and function: wall thickness, chamber volumes, valve movement and blood-flow velocities. A standard protocol includes more than 40 parameters. Echocardiography surpasses ECG for information about structural changes. Russian researchers (RGNKTs, RNIMU) trained a neural network (FCNN) to determine the heart's biological age from 5 key echocardiography parameters with an accuracy of ±5 years.

The percentage of blood the heart ejects with each contraction

The ejection fraction (EF) is the share of blood volume that the heart's left ventricle pushes into the aorta with each contraction. Normal: ≥55%. A drop to 40–54% is a moderate impairment, and <40% is systolic heart failure. With a reduced ejection fraction, the heart's biological age is usually higher than the chronological age. It is determined by echocardiography (a heart ultrasound).

A non-invasive method for assessing liver stiffness (fibrosis)

Elastography (for example, FibroScan / transient elastography) is a non-invasive method for measuring liver stiffness, which increases as fibrosis develops. It allows the fibrosis stage to be assessed without a biopsy; it is often supplemented by a measurement of steatosis (CAP).

Measuring liver stiffness by instrumental methods

Elastometry is the instrumental measurement of liver stiffness (elasticity), most often by transient elastography (FibroScan) or shear-wave elastography during ultrasound. The higher the stiffness, the more pronounced the fibrosis. It serves as a non-invasive alternative to biopsy for assessing the fibrosis stage.

The ability to be aware of and regulate feelings, and empathy

The level of development of the emotional sphere: self-awareness, managing one's own feelings, empathy, resilience to stress and the ability to move calmly through conflicts. Emotionally mature people set healthy boundaries and value long-term results. It is one of the key dimensions of mental age and develops throughout life.

Managing the strength and expression of one's emotions

The ability to monitor, evaluate and, when necessary, change one's emotional reactions — for example, to pause instead of responding impulsively to a slight. Well-developed emotional regulation is linked to resilience to stress and mature behavior in conflicts; its deficit shows as outbursts, "tantrums" and difficulty in hard conversations.

The ability to understand and share the feelings of others

The ability to recognize, understand and empathize with the emotional states of other people. A distinction is made between cognitive empathy (understanding another's point of view) and affective empathy (an emotional response). High empathy helps in relationships, but when overloaded it can lead to "absorbing" others' emotions. It is an important component of emotional maturity.

The volume of blood in the left ventricle at the end of diastole — before ejection

The end-diastolic volume (EDV) is the volume of blood accumulated in the left ventricle by the start of systole. Normal range: 80–150 mL (depending on age, sex and build). On echocardiography it is denoted LV_EDV. EDV decreases with age as the heart's chambers remodel. Together with the ejection fraction, it enters the calculation of stroke volume and cardiac output. In the RGNKTs study (2023) LV_EDV showed a correlation with age of |ρ| ≈ 0.55.

The inner lining of the vessels — the first line of defense against atherosclerosis.

The endothelium is the single-layer lining of the inner surface of all blood and lymphatic vessels. Its total area is about 700 m² and its mass 1.5–1.8 kg. It performs more than 30 functions: regulating vascular tone, anti-inflammatory protection, controlling blood clotting and a barrier function. Endothelial dysfunction is an early and key stage of atherosclerosis. Markers of damage: elevated homocysteine, high hs-CRP and microalbuminuria. It is reversible when risk factors are corrected.

An algorithm that predicts biological age from DNA methylation patterns

Epigenetic clocks (the Horvath Clock and its derivatives — GrimAge, PhenoAge, DunedinPACE) are mathematical models that predict biological age from DNA methylation patterns. They were developed by Steve Horvath (UCLA) in 2013 based on the analysis of 8,000 samples. GrimAge correlates most strongly with mortality and morbidity. DunedinPACE measures the pace of aging. They are considered the most accurate biomarker of aging of all that exist. They are the basis of most commercial biological-age tests.

The science of how lifestyle and environment control gene activity

Epigenetics is the field of biology that studies changes in gene activity that do not affect the DNA sequence. Epigenetic changes (methylation, histone acetylation) regulate which genes are "switched on" or "off." A key feature: unlike genetic mutations, epigenetic changes are reversible. Lifestyle, nutrition, stress and toxins all leave epigenetic "marks." This is precisely why biological age, unlike chronological age, can be changed.

The minimum fat needed for vital functions

The baseline level of fat needed for life: it supports the hormonal, reproductive and immune systems and is part of cell membranes and nervous tissue. It makes up about 2–5% of body mass in men and 10–13% in women. Falling below this level is dangerous to health.

Biological age from anthropometry, without lab tests

An approximate estimate of biological age from body composition (height, weight, waist and hip circumferences). It relies on the regular change in the ratio of fat to lean mass with age. It is a quick gauge of the pace of aging that does not replace laboratory and epigenetic methods.

The management of attention, task-switching and planning

A set of the brain's higher regulatory processes (mainly in the prefrontal cortex): planning, switching between tasks, inhibiting impulses, holding a goal and controlling attention. They determine the ability to quickly "switch" modes — for example, from focused work to conversation.

The population norm of "wear" for your age

The calculated biological age typical for the population at a given passport age. It serves as a benchmark: the difference between the estimated and the expected biological age (the index) shows whether the body is ahead of the age norm or behind it.

Fat-free mass / height²

The Fat-Free Mass Index is fat-free body mass relative to height squared (kg/m²) — analogous to BMI but for lean mass. It reflects muscular development independently of fat. The normalized FFMI adjusts the value to a height of 1.8 m so that people of different heights can be compared.

Fasting blood sugar — the main marker of carbohydrate metabolism

Fasting glucose is the concentration of sugar in blood plasma after 8–12 hours without food; it is the main indicator of carbohydrate metabolism. Normal range: 3.9–6.1 mmol/L. A value ≥ 5.6 mmol/L already counts as a criterion of metabolic syndrome; 6.1–6.9 mmol/L is impaired fasting glucose (prediabetes); ≥ 7.0 mmol/L on repeat measurement is the threshold for diabetes mellitus. Chronically elevated glucose damages the vessels and accelerates aging.

The mass of all the body's fat

The mass of all the body's lipids — both essential (in cell membranes, for hormone synthesis) and stored (subcutaneous and visceral fat). Together with fat-free mass it makes up total body mass. It is estimated via body-fat percentage: fat mass = weight × body-fat % / 100.

The whole body except fat

Fat-free mass is body mass without adipose tissue: skeletal muscle, bone, water, organs and connective tissue. It determines metabolism, strength and functional resilience. It is calculated as weight × (1 − body-fat % / 100); normally it makes up ~74–80% of body mass in men and ~64–80% in women.

The iron-storage protein of the body

The main protein that stores iron in the body. It is a marker of iron reserves. A low ferritin (<30 ng/mL in women, <50 ng/mL in men) indicates iron deficiency. A high ferritin is a marker of inflammation or iron overload.

The age of your physical condition

Fitness age shows how "young" the body works in terms of physical condition. It is made up of cardiorespiratory fitness, strength, neuromotor function, body composition and lifestyle, and can differ markedly from passport age in either direction. Unlike laboratory biological age, fitness age is assessed by functional tests and habits and responds quickly to training.

An artery's ability to widen in response to increased blood flow

Flow-Mediated Dilation is the increase in the diameter of an artery (usually the brachial) in response to a temporary rise in blood flow, expressed as a percentage of the baseline diameter (%FMD). It reflects nitric oxide production by the endothelium and is considered a marker of endothelial function: the higher the %FMD, the "younger" and healthier the vessels. It is measured in a provocation test (for example, with the AngioDefender device).

The ability to solve new problems without relying on past experience

Fluid intelligence is the ability to reason logically, find patterns and solve unfamiliar problems independently of accumulated knowledge. It relies on processing speed and working memory, naturally declines with age but can be trained. It is contrasted with crystallized intelligence (accumulated knowledge and vocabulary), which, on the contrary, grows with age.

A water-soluble vitamin for DNA synthesis, cell division and homocysteine metabolism.

Folic acid (B9) is the synthetic form of folate found in supplements and fortified foods. The natural form — folate — is in leafy vegetables, legumes and liver. It participates in the synthesis of nucleotides (DNA and RNA), in methylation and in the remethylation of homocysteine. Deficiency → hyperhomocysteinemia, megaloblastic anemia and neural-tube defects in the fetus. Daily requirement: 400 µg (800–1000 µg with elevated homocysteine or in pregnancy). With the MTHFR C677T mutation the active form — methylfolate (5-MTHF) — is more effective.

A non-immune reaction to certain foods, causing bloating, fatigue and headaches — often not connected to food.

Unlike allergy (IgE), food intolerance is mediated by other mechanisms (IgG, enzyme deficiency, FODMAPs). Symptoms may appear 24–72 hours after eating a food, which complicates diagnosis. It is identified by breath tests (lactose, fructose) and elimination diets.

The main thyroid hormone

Thyroxine (T4) is the main thyroid hormone; in the tissues it is converted into the more active T3. Free T4 is assessed together with TSH: their combination distinguishes overt from subclinical hypothyroidism and hyperthyroidism.

The active thyroid hormone

Triiodothyronine (T3) is the most active thyroid hormone, formed mainly from T4 in the tissues. Free T3 is part of the extended panel used with pronounced symptoms to clarify the nature of the dysfunction.

Glomerular filtration rate — an indicator of kidney function

GFR (glomerular filtration rate, eGFR) is the volume of blood cleared by the kidneys per minute. Normal: >90 mL/min/1.73m². A reduced GFR indicates chronic kidney disease: 60–89 is a mild reduction, 30–59 a significant one, and <30 a severe reduction of function.

A liver enzyme — the most sensitive marker of cholestasis and alcohol-related damage

GGT (Gamma-Glutamyl Transferase) is a cell-membrane enzyme highly active in the liver, pancreas and kidneys. It is the most sensitive marker of biliary-tract disease and alcoholic liver damage — it rises earlier than other enzymes. Normal range: up to 50 U/L (men), up to 30 U/L (women). It also rises in metabolic syndrome, non-alcoholic fatty liver disease and drug toxicity. In the Bortz Blood Age model log(GGT) enters with one of the largest positive coefficients.

The age of DNA from epigenetic marks

Genetic age is determined from DNA methylation (epigenetic clocks) and telomere length. It reflects the genomic damage accumulated over the years lived. It can differ substantially from chronological age in either direction depending on lifestyle.

Diabetes first detected during pregnancy

Gestational diabetes is a disturbance of carbohydrate metabolism first detected during pregnancy. It usually resolves after delivery, but it is a recognized risk factor for later type 2 diabetes — both in the mother and in association with the birth of a large baby (> 4 kg). Women with this history are advised to have regular glucose and HbA1c monitoring.

A fraction of plasma proteins; calculated as total protein − albumin

Globulins are a group of blood-plasma proteins (including immunoglobulins and transport proteins), calculated as the difference between total protein and albumin. A rise in globulins may accompany chronic inflammation and the progression of liver disease; this parameter is included in fibrosis indices (for example, SAFE).

Sugar molecules on the surface of proteins — a marker of inflammation and biological age

Glycans are complex carbohydrate structures attached to proteins and lipids on the cell surface. IgG glycomics (analysis of the glycans on immunoglobulin G) reflects the level of systemic inflammation and correlates with biological age. GlycanAge is a commercial test that uses this approach. Advantage: high sensitivity to inflammation. Limitation: a narrow focus that does not capture other aging mechanisms (methylation, telomeres). Glycan composition changes with diet, exercise and stress.

HbA1c — an indicator of blood sugar over 3 months

HbA1c (hemoglobin A1c) is the fraction of hemoglobin bound to glucose. It reflects the average blood glucose level over the last 2–3 months. Normal range: <5.7%. The diagnostic criterion for diabetes mellitus is ≥6.5%.

Substances that interfere with iodine uptake

Goitrogens are compounds that hinder the thyroid gland's uptake of iodine (found in soy and raw cruciferous vegetables — cabbage, radish, broccoli). With adequate iodine and cooking their effect is small, but in hypothyroidism it is worth limiting an excess of raw cruciferous vegetables and soy.

Autoimmune hyperthyroidism

Graves' disease (diffuse toxic goiter) is an autoimmune disease in which antibodies stimulate TSH receptors and drive the thyroid gland to produce an excess of hormones. It is the most common cause of hyperthyroidism: it presents with a rapid heartbeat, weight loss, anxiety and sometimes eye symptoms.

A second-generation epigenetic clock — the best predictor of mortality and disease

GrimAge is a second-generation epigenetic clock developed by Steve Horvath (UCLA, 2019). It is trained to predict "time to death" rather than chronological age. It combines 8 DNA-methylation-based biomarkers (including smoking level, mobility, and several plasma proteins) plus chronological age. The deviation of GrimAge from chronological age (GrimAge acceleration) is one of the most accurate predictors of mortality, cardiovascular events and age-related disease. The MIDUS study found that stress and lifestyle explain 43% of the variance in GrimAge acceleration.

The trillions of microorganisms in the gut that affect immunity, metabolism, mood and nutrient absorption.

A disruption of the microbiome's composition (dysbiosis) is linked to inflammatory diseases, obesity and depression. It is analyzed by 16S rRNA sequencing. Probiotics, diet and lifestyle have a direct effect on the microbiome's composition.

Fat predominantly on the hips and buttocks

A fat-distribution pattern dominated by deposits in the lower body — the hips and buttocks (the "pear" shape). The subcutaneous fat of these areas is metabolically less dangerous than visceral fat, so this type is linked to lower cardiometabolic risk. It is more common in women under the influence of estrogen and is reflected in a low WHR.

"Good" high-density cholesterol

High-density lipoproteins (HDL) carry excess cholesterol from the vessel walls back to the liver. A low level (men ≤ 1.0; women ≤ 1.2 mmol/L) is a component of metabolic syndrome and an independent cardiovascular risk factor.

A plasma protein; its level changes with liver fibrosis

Haptoglobin is a plasma protein that binds free hemoglobin. It is synthesized by the liver and is an acute-phase protein; as fibrosis progresses its level falls, which is why it is included in the FibroTest. In hemolysis it drops sharply (distorting the result).

A formula for calculating basal metabolism from sex, height, weight and age

A classic formula for estimating the basal metabolic rate (BMR), proposed in 1918–1919 and refined by Roza & Shizgal in 1984. It calculates resting daily energy expenditure from sex, body weight, height and age. It underlies the estimated metabolic age.

The maximum number of cell divisions — about 40–60 times

The Hayflick limit is a biological limit on the number of divisions of human somatic cells, discovered by Leonard Hayflick in 1961. It is about 40–60 divisions for most cells. Once this limit is exhausted, the cell enters senescence or triggers apoptosis. It is caused by the progressive shortening of telomeres with each division.

A scheduled medical examination

A set of medical measures aimed at the early detection of diseases and their risk factors. It includes doctors' examinations and laboratory and instrumental investigations.

The years of life lived free of serious chronic disease

Healthspan is the period of life lived without serious chronic disease and loss of functional independence, as opposed to lifespan — the total length of life. A goal of modern gerontology is to narrow the gap between the two — that is, to extend the healthy years specifically.

The heart's functional age from ECG and AI

Heart biological age is a measure that reflects the true functional state of the cardiovascular system independently of passport age. It is determined by AI algorithms from ECG parameters: QRS duration, the QT interval, ejection fraction and other markers. If the heart's biological age exceeds the chronological age by 7+ years, all-cause mortality risk rises by 62% and MACE risk by 92%. If the heart is "younger" by 7 years, the risks fall by 14–27%.

The difference between the maximum and resting heart rate

Heart rate reserve (HRR) = maximum HR − resting heart rate. It shows the heart's "margin" between the calm state and its limit. The larger the reserve (usually thanks to a low resting rate in trained people), the higher the functional capacity of the cardiovascular system. It is used in the Karvonen formula to calculate training zones.

Ranges of heart rate by exercise intensity

Heart-rate zones are ranges of heart rate (as a % of maximum HR) that set the intensity of a workout: Zone 1 recovery (50–60%), Zone 2 fat-burning / aerobic base (60–70%), Zone 3 aerobic (70–80%), Zone 4 threshold (80–90%), Zone 5 VO₂max (90–100%). Training in different zones develops different qualities; for health and longevity the aerobic base (Zone 2) is especially valuable.

The oxygen-carrying protein of red blood cells

Hemoglobin (Hb) is the iron-containing protein of red blood cells that carries oxygen from the lungs to the tissues. Normal range: men 130–170 g/L, women 120–155 g/L. A decrease (<120 g/L) is anemia. In iron deficiency, hemoglobin synthesis is the first to fail, causing fatigue, shortness of breath and pallor.

The destruction of red blood cells, releasing hemoglobin into the plasma

Hemolysis is the destruction of red blood cells with release of hemoglobin. It lowers haptoglobin and raises bilirubin for reasons unrelated to the liver, so during hemolysis the FibroTest becomes unreliable.

The main working cell of the liver

Hepatocytes make up about 80% of the liver's mass and perform its key functions: detoxifying toxins, synthesizing proteins and bile, and regulating glucose and fat metabolism. In fatty liver disease, fat droplets accumulate inside hepatocytes (steatosis); the diagnosis is made when fat is found in more than 5% of these cells.

The hormone that regulates iron metabolism

Hepcidin is a peptide hormone synthesized by the liver. It is the main regulator of iron homeostasis: it blocks the export of iron from the intestine, macrophages and storage cells by degrading ferroportin. In inflammation, infection and cancer, hepcidin rises sharply → iron is "locked" inside cells → the anemia of chronic disease develops. In iron deficiency, hepcidin is suppressed → absorption increases.

Share of young, RNA-rich reticulocytes — a marker of erythropoiesis intensity

HLR% (High Light Scatter Reticulocyte percentage) is the percentage of the youngest reticulocytes, which scatter light strongly because of their high RNA content. It is reported by Sysmex hematology analyzers. Normal range: 0.2–2.0%. A rise indicates active erythropoiesis — for example after blood loss or in response to iron-deficiency anemia therapy. It is a UK Biobank parameter and is not part of a standard clinical blood count.

The biologically active form of vitamin B12 in the blood — the earliest marker of B12 deficiency, detecting it years before symptoms.

It reflects the amount of B12 available to the cells. It falls earlier than total B12, homocysteine and MMA. Normal >35 pmol/L, <20 pmol/L is overt deficiency. The WHO recommends it as a first-line test for screening B12 deficiency.

A sulfur-containing amino acid — a marker of the risk of heart attack, stroke and dementia. It rises with a deficiency of B12, B9 or B6.

An intermediate product of methionine metabolism. It is neutralized by enzymes with the participation of vitamins B9, B12 and B6. When these are deficient it accumulates, damaging the vascular endothelium and neurons. Optimal level: <10 µmol/L. Laboratory normal: <15 µmol/L. A meta-analysis of 30 studies (JAMA, 2002): each +5 µmol/L → +20% risk of coronary heart disease. The Framingham Study (NEJM, 2002): a level >14 µmol/L nearly doubles the risk of Alzheimer's disease.

The benefit of small doses of a stressor that is harmful in large doses

Hormesis is a biological phenomenon in which moderate, measured stress (fasting, exercise, sauna heat, cold) triggers the cell's protective and repair mechanisms and ultimately makes the body more resilient. The same factor in a large dose is harmful — dose and recovery decide everything.

An elevated blood homocysteine level — an independent risk factor for cardiovascular disease and dementia.

A condition in which the plasma homocysteine concentration exceeds 15 µmol/L. Classification: mild (15–30), moderate (30–100), severe (>100 µmol/L). The mild form occurs in 5–12% of the population of developed countries. Causes: deficiency of vitamins B9, B12 and B6; the MTHFR C677T mutation; chronic kidney disease; hypothyroidism; and certain drugs (metformin, methotrexate). Treatment: B vitamins lower the level by 25–33%.

Excess production of parathyroid hormone

A condition with increased secretion of parathyroid hormone (PTH). In primary hyperparathyroidism, PTH excessively "leaches" calcium from the bones, raising its blood level and lowering bone density; in secondary hyperparathyroidism it is a response to chronic calcium or vitamin D deficiency. It affects calcium metabolism and bone health.

Overactivity of the thyroid gland

Hyperthyroidism is an increased production of thyroid hormones, so metabolism speeds up. It presents with a rapid heartbeat, weight loss despite a normal appetite, anxiety, tremor, sweating and poor heat tolerance. It is the opposite of hypothyroidism.

A low blood calcium level

A fall in the blood calcium concentration below normal. It may present with muscle cramps and spasms, numbness and tingling (around the mouth, in the fingers), increased muscle excitability (tetany) and heart-rhythm disturbances. Causes include vitamin D deficiency, kidney disease, hypoparathyroidism and malabsorption.

Reduced thyroid function with insufficient production of thyroid hormones, leading to a slowdown of all metabolic processes.

Subclinical hypothyroidism (elevated TSH with normal T4) is often symptomless or presents nonspecifically: fatigue, feeling cold, weight gain and depression. It occurs in 4–10% of adults. It is diagnosed by TSH alone.

High-sensitivity CRP — a marker of cardiovascular risk

High-sensitivity C-reactive protein (hs-CRP) is a test with improved measurement precision. Values of 1–3 mg/L indicate moderate cardiovascular risk, and >3 mg/L indicates high risk. It is used to assess cardiovascular risk even in the absence of overt inflammation.

A high-sensitivity marker of heart-muscle damage

High-sensitivity troponin (hs-cTnI/T) is a heart-muscle protein released into the blood when the muscle is damaged. It is the standard for diagnosing acute myocardial infarction. It is also elevated in myocarditis, pulmonary embolism and heart failure.

Iron-deficiency anemia

Iron-deficiency anemia (IDA) is the most common type of anemia, caused by a shortage of iron. It presents with reduced hemoglobin, weakness, shortness of breath and pale skin. It is diagnosed by hemoglobin, ferritin and serum iron levels.

Insulin-like growth factor — a hormone driving tissue growth

IGF-1 (insulin-like growth factor 1) is a hormone that mediates the action of growth hormone and stimulates cell division. High levels are needed for growth in youth, but in adulthood chronically elevated IGF-1 is associated with accelerated aging and the risk of certain tumors. It falls with protein and calorie restriction.

An objective measure of cognitive ability

The Intelligence Quotient is a standardized measure of cognitive ability and problem-solving relative to the age norm. The concept goes back to the Binet–Simon scale (1905) and William Stern's idea. Unlike mental age, IQ is relatively stable in adulthood, is measured by standardized tests, and is used for clinical assessment.

The calculated weight for a healthy BMI range

An approximate body weight corresponding to a healthy body-mass-index range for your height. In the estimation calculator it is computed by the WHO formula: (height/100)²·21.745 with a sex adjustment. Reaching the ideal weight brings the metabolic age closer to the chronological age.

An intermediate state between normal and diabetes

Impaired glucose tolerance (IGT, prediabetes) is a condition in which blood sugar is above normal but still below the diabetic threshold. It indicates insulin resistance and substantially raises the risk of developing type 2 diabetes.

Blood substances (hs-CRP, interleukins, ESR) that indicate chronic inflammation — a key mechanism of aging and most chronic diseases.

Chronic low-grade inflammation ('inflammaging') underlies cardiovascular disease, diabetes and dementia. hs-CRP <1 mg/L is normal, 1–3 mg/L is moderate risk, >3 mg/L is high risk. It falls with a healthy diet, physical activity and normalized sleep.

The hormone that lets glucose into cells

Insulin is a pancreatic hormone that gives cells access to glucose from the blood. In insulin resistance, cells respond to it poorly, and to keep blood sugar normal the pancreas has to produce more and more insulin.

Reduced sensitivity of cells to insulin

A condition in which the body's cells respond insufficiently to the hormone insulin, leading to elevated blood glucose and insulin. It precedes the development of type 2 diabetes. It is assessed by the HOMA-IR index.

An eating schedule that alternates windows of eating and fasting

Intermittent fasting is an eating pattern in which meals are confined to a time window and the body fasts the rest of the time. Popular protocols: 16:8 (16 hours of fasting, an 8-hour eating window), 5:2, and alternate-day eating. It triggers autophagy and lowers insulin and mTOR activity. It affects body weight and metabolic markers; evidence for directly extending human lifespan is still limited.

The muscular wall between the right and left ventricles of the heart

The interventricular septum (IVS) is the muscular structure that separates the right and left ventricles. Normal thickness in diastole: 7–11 mm. Thickening of the IVS >12 mm is a sign of hypertrophy associated with hypertension, age-related remodeling or hypertrophic cardiomyopathy. In the RGNKTs study (2023) the IVS showed a correlation of |ρ| ≈ 0.72 with age — the second-strongest predictor of the heart's biological age after E/A.

A lack of iodine — the leading cause of hypothyroidism worldwide

Iodine is an essential building block of thyroid hormones. Its deficiency is the main cause of hypothyroidism and goiter on a global scale, with about 30% of the world's population at risk. It is replenished by seafood, fish, dairy products and iodized salt.

The uptake of iron in the intestine

Iron is absorbed mainly in the duodenum and proximal jejunum. Heme iron (from meat) is absorbed at 20–30%. Non-heme iron (from plants) at only 1–10%. Vitamin C enhances absorption 2–4 fold. Calcium, the tannins in tea and coffee, and the phytates in grains reduce absorption.

A shortage of iron in the body

Iron deficiency is the most common nutrient deficiency in the world, affecting ~2 billion people. Iron is needed for hemoglobin synthesis, oxygen transport and mitochondrial function. Stages: latent deficiency → iron-deficiency anemia. It is diagnosed by ferritin (<30 ng/mL), serum iron and the complete blood count.

International clinical guidelines for kidney disease

KDIGO (Kidney Disease: Improving Global Outcomes) is an international organization that develops clinical guidelines for diagnosing and managing kidney disease. The KDIGO guidelines (including the 2024 edition) define how to assess kidney function (the CKD-EPI equations), classify chronic kidney disease and plan follow-up.

A metabolic mode in which the body runs on ketone bodies from fat

Ketosis is a metabolic state in which, because of a shortage of carbohydrates, the liver begins to produce ketone bodies from fats and use them as fuel (primarily for the brain). It develops during prolonged fasting, intermittent fasting or a ketogenic diet. Ketone bodies (beta-hydroxybutyrate) have their own signaling activity, affecting inflammation and autophagy.

Low-density lipoproteins; they carry cholesterol into the vessel walls

LDL (low-density lipoproteins) carry cholesterol to the tissues, but in excess they deposit it in the artery walls, forming atherosclerotic plaques. This is a key cardiovascular risk factor — the lower the LDL, the better.

Analyses of blood, urine and other biomaterials

A set of methods for examining biological fluids (blood, urine, saliva, stool) to assess health. It includes biochemistry, the complete blood count, and hormonal, immunological and genetic tests.

Body mass without fat — muscle, bone, water, organs

Lean (fat-free) body mass = total weight minus fat mass. Muscle is metabolically active and accounts for a significant part of the basal metabolism: the more lean mass, the higher the resting energy expenditure and the "younger" the metabolism. Strength training and adequate protein help to preserve it.

Thickening of the wall of the heart's main chamber from pressure overload

A thickening of the muscular wall of the heart's left ventricle in response to prolonged pressure overload (in hypertension). Initially compensatory, over time it raises the risk of arrhythmias, heart failure and heart attack. It is detected on ECG and echocardiography and is one of the markers of target-organ damage in hypertension.

Scarring of the liver — the replacement of healthy tissue by connective tissue

Liver fibrosis is the gradual replacement of healthy liver tissue by connective (scar) tissue in response to chronic damage. It disrupts the organ's structure and function; the extreme stage is cirrhosis. Stages are assessed by the METAVIR (F0–F4) and Ishak (F0–F6) scales.

The firmness of liver tissue; it rises as scarring (fibrosis) progresses

Liver stiffness is the physical firmness of the tissue, related to the degree of its scarring. As fibrosis progresses, healthy tissue is replaced by connective tissue and the liver becomes denser. Stiffness is measured by elastography (FibroScan / transient elastography) or estimated by calculation models (for example, LSS); increased stiffness is a sign of fibrosis, up to cirrhosis.

Length of life, above all its healthy part

In the science of aging, longevity means not simply a large number of years lived (lifespan) but, above all, healthspan — the years of life free of chronic disease and loss of independence. The modern approach to longevity aims to slow biological aging rather than to treat individual diseases as they appear.

The main cells of adaptive immunity: T cells, B cells and NK cells

Lymphocytes are cells of adaptive and innate immunity: T cells (cellular immunity), B cells (antibodies) and NK cells (antiviral and antitumor defense). Normally they make up 18–40% of leukocytes, with an absolute count of 1.2–3.0 ×10⁹/L. A drop in the lymphocyte percentage is an indicator of immunosenescence and chronic inflammation and is associated with increased mortality. Biological-age models (PhenoAge, Bortz) use precisely the lymphocyte percentage — a fall below normal raises PhenoAge.

Major adverse cardiovascular events

MACE (Major Adverse Cardiovascular Events) is a composite endpoint used in cardiology trials. It includes myocardial infarction, stroke and cardiovascular death. A heart biological age exceeding chronological age by 7+ years raises MACE risk by 92% — a key finding of the EHRA 2025 study based on 500,000 ECGs.

How much hemoglobin a single red blood cell carries, in picograms

MCH (Mean Corpuscular Hemoglobin) is the average amount of hemoglobin in a single red blood cell. Normal range: 27–33 pg. A decrease (hypochromia) occurs in iron-deficiency anemia and thalassemia. An increase (hyperchromia) occurs in B12/folate deficiency and liver disease. It is calculated as Hb/RBC and is a standard parameter of the complete blood count.

Mean corpuscular volume — the size of red blood cells

MCV (Mean Corpuscular Volume) is a complete-blood-count parameter. Normal range: 80–100 fL. In iron deficiency MCV falls below 80 fL (microcytosis): the cells lack enough hemoglobin to grow normally. An increase above 100 fL (macrocytosis) is characteristic of B12 or folate deficiency.

A liver fibrosis staging scale from F0 to F4

METAVIR is a histological scale for staging liver fibrosis: F0 (no fibrosis), F1 (portal fibrosis without septa), F2 (with occasional septa), F3 (numerous septa without cirrhosis) and F4 (cirrhosis). It is widely used to assess the progression of chronic liver disease.

A non-insulin index of insulin sensitivity

The Metabolic Score for Insulin Resistance (Bello-Chavolla, 2018) is a surrogate index of insulin resistance that requires no insulin assay. METS-IR = ln((2·glucose) + triglycerides) · BMI / ln(HDL), with blood values in mg/dL. It predicts visceral obesity and incident type 2 diabetes; the high-risk threshold is 50.39.

Mean red-cell volume after isovolumetric sphering — a precise measure of cell size

MSCV (Mean Sphered Cell Volume) is a parameter measured by automated Sysmex XE/XN-series hematology analyzers after isovolumetric sphering of red blood cells. It gives a more accurate estimate of mean cell volume than the classic MCV, which depends on cell shape. It is used in UK Biobank research. Normal range: 80–95 fL. It is not part of standard clinical tests in most laboratories.

The gene for a folate-cycle enzyme. The C677T mutation lowers its activity and raises homocysteine.

MTHFR (methylenetetrahydrofolate reductase) is the enzyme that catalyzes a key reaction of the folate cycle: the conversion of 5,10-MTHF into 5-MTHF (active folate). The C677T polymorphism (a cytosine-to-thymine substitution at position 677) lowers enzyme activity by 30% (heterozygotes) or 65% (TT homozygotes). The homozygous TT form occurs in ~10% of Europeans. The consequence is impaired remethylation of homocysteine and its accumulation. With this polymorphism ordinary folic acid works less well — the active form, methylfolate (5-MTHF), is recommended.

A participant in more than 300 biochemical reactions: ATP synthesis, blood-sugar regulation, muscle and nervous-system function, and blood pressure.

99% of magnesium is inside cells, so a standard serum test poorly reflects true status. Symptoms of deficiency: cramps, anxiety, insomnia and arrhythmia. Risk groups: stress, diabetes, diuretics and alcohol abuse.

Normal blood pressure in the clinic but elevated outside it

A condition in which blood pressure is normal in the doctor's office but elevated outside the clinic (at work, under stress, at home, during sleep). It is suspected more often with high-normal blood pressure (130–139/85–89). It is dangerous because it covertly damages organs and is associated with roughly a doubling of cardiovascular risk. It is detected by home and 24-hour blood-pressure monitoring.

The highest heart rate at the limit of exertion

The maximum heart rate (max HR) is the greatest number of heartbeats per minute at peak exertion. It declines with age and is estimated by the Tanaka formula: 208 − 0.7 × age (more accurate than the outdated "220 − age"). Heart-rate zones are calculated from it. The exact value is determined by an exercise stress test.

The average force of blood pressure over a cardiac cycle

Mean arterial pressure (MAP) is the averaged pressure of blood on the artery walls over a single cardiac cycle, a key measure of organ perfusion. It is calculated as DBP + ⅓ of pulse pressure (or (SBP+2·DBP)/3). Normal range 70–100 mmHg; keeping it ≥65 mmHg is critical to prevent hypoperfusion.

A diet emphasizing vegetables, fish, olive oil and whole foods

The Mediterranean eating pattern emphasizes vegetables, fruit, legumes, whole grains, fish, nuts and olive oil, while limiting red meat, sugar and processed foods. In studies it is linked to reduced cardiovascular risk and slower aging. Adherence is often scored by an index (for example, 0–14 points).

The age of your mind: psychological and emotional maturity

A concept from developmental psychology: a person's level of psychological, emotional and cognitive development independent of chronological age. By the American Psychological Association's definition, it is "the level of mental development expressed as the age at which it is normally reached." Unlike IQ, mental age is dynamic and changes with life experience; "higher" does not mean "better" — it is a multidimensional personality profile, not a score.

An assessment of insulin resistance from triglycerides, glucose and HDL

A Russian non-insulin surrogate index of insulin resistance (Roitberg G.E.). MI = triglycerides × glucose / HDL² (all values in mmol/L). It is sensitive to early shifts in carbohydrate and lipid metabolism. Threshold: MI ≥ 7.0 indicates insulin resistance.

The age of metabolism from body composition

Metabolic age is determined from the basal metabolic rate and compared with average data for different age groups. A metabolic age below the chronological one is a sign of an active metabolism and good physical condition.

A cluster of cardiometabolic risk factors

Metabolic syndrome is a combination of abdominal obesity, elevated blood pressure, impaired carbohydrate metabolism (insulin resistance) and dyslipidemia. It substantially raises the risk of type 2 diabetes and cardiovascular disease.

All the chemical processes that transform energy and substances

Metabolism is the set of chemical reactions that convert the substances taken in with food into energy and building material for cells. Its rate changes with age and depends on muscle mass, hormonal status, nutrition, sleep and physical activity.

An essential sulfur-containing amino acid — the precursor of homocysteine in the metabolic cycle.

Methionine is an essential amino acid obtained from protein foods (meat, fish, eggs, legumes). In the body it is used to synthesize proteins, the antioxidant glutathione and SAM (S-adenosylmethionine) — the universal donor of methyl groups. Homocysteine is formed during methionine metabolism. When the methionine cycle works normally (with B12 and folate), homocysteine is remethylated back to methionine or directed into harmless cysteine (with B6).

A reduction in the size of red blood cells

Microcytosis is a condition in which the mean corpuscular volume (MCV) falls below 80 fL. The most common cause is iron deficiency: the cells lack enough hemoglobin to develop normally and remain small and pale (hypochromic). Other causes: thalassemia, the anemia of chronic disease and lead poisoning.

An intermediate state between normal and dementia — risk is raised, but independence is preserved

Mild Cognitive Impairment (MCI) is a state in which cognitive impairment goes beyond normal aging, but the person retains the ability to live independently. In some people MCI does not progress, in some it improves, but on average the risk of dementia is significantly higher than in the general population. It is considered the most important window for intervention. It is diagnosed by neuropsychological tests (MMSE, MoCA).

The cell's "power plants" — their dysfunction accelerates aging

Mitochondria are cellular organelles that produce energy in the form of ATP through oxidative phosphorylation. They contain their own DNA (mtDNA). With age, mitochondrial function declines: mtDNA mutations accumulate, free-radical production increases (oxidative stress) and ATP production falls. Mitochondrial dysfunction is one of the "hallmarks of aging" (López-Otín). Mitochondrial function can be improved by exercise, resveratrol, NAD+ precursors (NMN, NR) and intermittent fasting.

Large white blood cells that mature into macrophages — they regulate inflammation

Monocytes are the largest white blood cells; they circulate in the blood for 1–3 days and then migrate into tissues and become macrophages or dendritic cells. Normal absolute count: 0.09–0.6 ×10⁹/L (3–11%). An increase occurs with chronic infections, autoimmune diseases and monocytic leukemia. They are linked to age-associated inflammation: an elevated monocyte level enters the Bortz Blood Age model with one of the largest positive coefficients.

How many times higher the risk of death is than at a normal weight

It shows the risk of all-cause mortality relative to a normal weight, which is set at 1.00 (BMI 18.5–25). A value of 1.30 means a risk 30% above normal. It is calculated from the curves of a large meta-analysis (Lancet, 2016): the relationship is U-shaped — risk rises both with excess weight and with being underweight.

Thickening of the heart walls in response to increased load

Myocardial hypertrophy is an increase in heart-muscle mass through thickening of the ventricular walls. It develops as an adaptation to chronic load: arterial hypertension, aortic stenosis, or intense physical training (athlete's heart). Concentric hypertrophy (RWT ≥ 0.42, IVS >12 mm) is the typical response to hypertension and often accompanies age-related remodeling. It is diagnosed by echocardiography and is an independent risk factor for cardiovascular events.

Death of a part of the heart muscle from complete blockage of a coronary artery — an acute, life-threatening condition.

It occurs when an atherosclerotic plaque ruptures and a thrombus forms that blocks a coronary artery. Without restoration of blood flow, the myocardial cells die irreversibly within 20–40 minutes. Symptoms: crushing chest pain behind the sternum, shortness of breath, sweating and pain in the left arm. Emergency treatment: thrombolysis or stenting. The main marker: troponin I/T in the blood.

The muscle protein that stores oxygen

Myoglobin is an iron-containing protein of muscle cells that stores a reserve of oxygen for muscle work. About 10% of the body's iron is contained in myoglobin. In iron deficiency, muscle performance declines — this is one of the causes of muscle weakness and exercise intolerance in iron-deficiency anemia. It rises in the blood with muscle damage.

A cellular nutrient sensor and regulator of growth and aging

mTOR (mechanistic target of rapamycin) is a signaling protein that switches on cell growth and division when nutrients are abundant and suppresses autophagy. Chronic excess mTOR activity (overeating, excess protein) is linked to accelerated aging; moderately lowering it — through fasting, calorie restriction or rapamycin — extends lifespan in experiments.

Non-alcoholic (metabolically associated) fatty liver disease

NAFLD is a chronic liver disease linked to metabolic dysfunction, in which fat accumulates in more than 5% of liver cells (hepatocytes) — macrovesicular steatosis — in the absence of significant alcohol use. Since 2023 the international classification has used a more precise name, MASLD (metabolic dysfunction-associated steatotic liver disease), emphasizing the link with obesity, insulin resistance and metabolic syndrome.

Non-alcoholic steatohepatitis — the inflammatory form of fatty liver disease

NASH (non-alcoholic steatohepatitis) is an inflammatory, infiltrative process in the parenchyma and stroma of the liver with foci of fibrosis, developing on the background of fatty liver disease (NAFLD). Unlike simple steatosis, in NASH inflammation and cell damage are added to the fat accumulation, which raises the risk of progression to fibrosis and cirrhosis.

The U.S. National Health and Nutrition Examination Survey — the basis for PhenoAge

NHANES (National Health and Nutrition Examination Survey) is a program of the U.S. Centers for Disease Control and Prevention (CDC) that has assessed the health and nutrition of a representative sample of the population since the 1960s. It includes questionnaires, physical examination and laboratory tests. Data from NHANES-III (1988–1994), with subsequent mortality follow-up, formed the basis of the PhenoAge model (Levine et al., 2018).

A marker of heart failure

NT-proBNP (N-terminal pro-B-type natriuretic peptide) is a biomarker released by heart cells under increased load or injury. It is used to diagnose and monitor heart failure. It rises with pressure and volume overload.

An AI algorithm that mimics the working of the brain's neurons — the basis of predictive medical models

A neural network is a computational model made of layers of interconnected "neurons" that learn from data. An FCNN (Fully Connected Neural Network) is an architecture in which each neuron is connected to every neuron of the next layer. In the RGNKTs study (2023), an FCNN with 10 hidden layers (Keras) was used to predict biological age from echocardiography data. The mean absolute error (MAE) was ~5 years, R² = 0.77–0.78.

The progressive death of neurons — the basis of Alzheimer's, Parkinson's and dementias

Neurodegeneration is a pathological process of the gradual loss of neuronal structure and function, leading to their death. Alzheimer's disease is based on the accumulation of amyloid plaques and tau neurofibrillary tangles. Neurodegenerative processes begin 15–20 years before the first clinical symptoms appear, which underscores the importance of early prevention.

The formation of new neurons, including in the adult brain

The process of forming new neurons from neural stem cells. In adults it persists mainly in the hippocampus (the region of memory and learning). It is stimulated by aerobic exercise, learning and growth factors (for example, BDNF), and suppressed by chronic stress, sleep deprivation and inflammation.

An inflammatory process in the brain — chronic neuroinflammation destroys neurons

Neuroinflammation is the activation of the brain's immune cells (microglia and astrocytes) in response to injury, infection or pathological proteins. Acute neuroinflammation protects the brain. Chronic low-grade neuroinflammation, sustained by amyloid, metabolic disorders and systemic inflammation, gradually damages neurons. It is considered one of the key mechanisms of neurodegeneration. As a marker, an elevated hs-CRP correlates with dementia risk.

Coordination, balance and movement control

Neuromotor functions are the nervous system's ability to control the muscles precisely: balance, coordination, reaction speed and proprioception. They are among the first to deteriorate with age and are directly linked to the risk of falls and injuries. They are trained by exercises for balance, coordination and core stabilization.

The main cells of the nervous system, transmitting electrical and chemical signals

Neurons are highly specialized cells of the central nervous system that form the basis of thinking, memory and perception. The brain contains ~86 billion neurons. With age, the speed of signal transmission between neurons declines and some cells die. In neurodegenerative diseases, neuronal death is accelerated and pathological. Neurons hardly regenerate, so protecting them is critically important.

The brain's ability to rewire connections and form new ones

The nervous system's property of changing its structure and function in response to experience: forming new synapses, redistributing functions between areas and recovering after damage. High neuroplasticity makes it easier to learn new things, adapt to change and recover from stress. It is supported by learning, physical activity, good-quality sleep and novel tasks.

The most numerous white blood cells — the first line of defense against bacteria

Neutrophils are the main granulocyte fraction, engulfing bacteria and fungi (phagocytosis). Normal absolute count: 2.0–7.0 ×10⁹/L (40–75% of all leukocytes). An increase occurs with bacterial infections, acute inflammation, stress and after exercise. A decrease occurs with viral infections, chemotherapy and autoimmune neutropenia. A chronically high neutrophil level is linked to the systemic inflammation of aging (inflammaging) and an older biological age.

A vasodilator molecule that widens blood vessels

A gaseous signaling molecule produced by the vascular endothelium. It relaxes the smooth muscle of the vessel wall and causes vessel widening (vasodilation), regulating blood flow and pressure. A decline in NO production is an early sign of endothelial dysfunction and vascular aging; it is precisely NO production that the %FMD test indirectly assesses.

A moderate reduction in bone density — the pre-stage of osteoporosis

A condition in which bone mineral density is below normal but does not yet reach the osteoporosis threshold. It is regarded as an early warning and a risk factor for future fractures; at this stage adequate calcium and vitamin D intake and weight-bearing exercise are especially important.

A reduction in bone density with a high risk of fractures

A skeletal disease in which bone mineral density decreases and the microarchitecture of bone tissue is disrupted, making bones brittle and prone to fracture (often with minimal trauma). Chronic calcium and vitamin D deficiency is one of the risk factors. It is diagnosed by densitometry (DEXA).

An imbalance of free radicals and antioxidants — it damages neurons and accelerates aging

Oxidative stress arises when free radicals (reactive oxygen species, ROS) accumulate faster than the body can neutralize them with antioxidants. Neurons are especially vulnerable to oxidative damage because of the brain's high metabolic activity. Chronic oxidative stress damages neuronal membranes, DNA and mitochondria, accelerating neurodegeneration. It is reduced by physical activity and a Mediterranean diet.

Polymerase chain reaction — a method of genetic diagnostics

PCR (polymerase chain reaction) is a molecular-biology method for repeatedly copying (amplifying) DNA fragments. It is used to diagnose infections, genetic mutations and tumor markers. It has very high sensitivity and specificity.

A measure of platelet size variability — higher with active megakaryocytopoiesis

PDW (Platelet Distribution Width) is a measure of the heterogeneity of platelet size. Normal range: 9–17%. It rises with increased platelet production (after bleeding, in immune thrombocytopenia) and in cardiovascular disease and diabetes. It is associated with a higher risk of thrombosis and adverse outcomes. In the Bortz Blood Age model PDW enters with a small positive coefficient.

A validated 10-item perceived stress scale

The Perceived Stress Scale-10 (PSS-10) is a psychometric instrument developed by Sheldon Cohen (1983). It measures perceived stress over the past month with 10 questions on a 5-point Likert scale. It has been validated in dozens of countries and languages and is used in clinical practice, epidemiology and corporate health.

Rank-based sensitivity of the pituitary to free T4

The Parametric Thyroid Feedback Quantile-based Index (Laclaustra, 2019) is a parametric index of central sensitivity to thyroid hormones. It compares the position of free T4 and TSH relative to a reference population (NHANES): PTFQI = Φ((fT4−10.075)/2.155) + Φ((ln TSH−0.4654)/0.7744) − 1. Normal range −0.4 to 0.4; high values indicate reduced sensitivity (TSH higher than expected for the fT4 level). The value depends on a given laboratory's fT4 scale, so it is read as a guide rather than an absolute.

The parathyroid-gland hormone that regulates calcium levels

A hormone of the parathyroid glands and the main regulator of blood calcium: it raises it by increasing the release of calcium from bone, its reabsorption in the kidneys and the activation of vitamin D. In chronic calcium deficiency, PTH rises, "leaching" calcium from the bones. It is part of the extended workup for calcium deficiency.

A subjective assessment of the level of stress

The degree to which a person perceives life events as uncontrollable, unpredictable and overwhelming. It is measured by the PSS-10 scale (Cohen et al., 1983). It is the subjective perception, rather than objective events, that drives the physiological stress response.

Phenotypic biological age from 9 blood markers

PhenoAge (Phenotypic Age) is a biological age calculated from 9 blood biochemistry markers plus chronological age. It was developed by Morgan Levine et al. (2018) on NHANES-III data using Cox regression to predict mortality. It includes: albumin, creatinine, glucose, hs-CRP, lymphocyte percentage, MCV, RDW-CV, alkaline phosphatase and white blood cell count. The excess of PhenoAge over chronological age (PhenoAge acceleration) predicts mortality better than chronological age itself. It is the standard "blood biological age", validated across dozens of cohorts.

A pathological craving for inedible substances

Pica is a disorder in which a person craves inedible substances: ice (pagophagia), earth, chalk, paper and clay. It often occurs with marked iron deficiency — pagophagia (a craving for ice) is especially characteristic. The mechanism is not fully understood but is linked to iron deficiency in brain tissue.

An isometric test of core-muscle endurance

The plank is an exercise and test in which the body is held straight, supported on the forearms and toes. The hold time reflects the static endurance of the core muscles (abdominals, back, stabilizers), which are important for posture, spine protection and transferring force between the upper and lower body.

The fraction of blood volume occupied by platelets

PCT (Plateletcrit) is the percentage of blood volume occupied by platelets, calculated as platelet count × mean platelet volume. Normal range: 0.15–0.40%. A decrease occurs with thrombocytopenias and splenomegaly. An increase occurs with thrombocytoses, inflammation and after splenectomy. In the Bortz Blood Age model plateletcrit has one of the largest negative coefficients: a higher plateletcrit is associated with a younger biological age.

Blood cells for clotting; their number falls with liver fibrosis

Platelets are formed blood elements involved in clotting. With progressive fibrosis and cirrhosis their number usually falls, which is why they are in the denominator of fibrosis indices, including FIB-4 (the lower the platelets, the higher the index).

Sugar above normal but not yet diabetes — a reversible "yellow zone"

Prediabetes is a disturbance of carbohydrate metabolism in which the glucose level exceeds normal but does not meet the criteria for diabetes mellitus (impaired fasting glucose and/or impaired glucose tolerance). Criteria: fasting glucose 5.55–6.98 mmol/L or HbA1c 5.7–6.4%. It is often symptomless. An important feature is reversibility: weight loss, diet and activity can return sugar to normal or substantially delay the development of diabetes.

How quickly the brain perceives and responds to information

The speed at which the brain takes in information, processes it and forms a response. It affects everything — from the pace of conversation to reactions on the road. It naturally declines with age, but quick-decision tasks, aerobic exercise and sleep help to maintain it.

The difference between systolic and diastolic blood pressure

The difference between systolic and diastolic pressure (for example, 120−80 = 40 mmHg). It reflects the stiffness of the large arteries: with age and atherosclerosis the vessels lose elasticity and pulse pressure rises. A high pulse pressure is an independent marker of cardiovascular risk and vascular aging.

The electrical signal of ventricular contraction on the ECG

The QRS complex is the central part of the ECG, reflecting depolarization (excitation) of the heart's ventricles. Normal duration: 80–120 ms. A widened QRS (>120 ms) indicates intraventricular conduction disturbances (bundle branch block), cardiomyopathy or heart failure. AI algorithms use QRS parameters as one of the key markers of the heart's biological age.

The time of a full electrical cycle of the heart's ventricles

The QT interval is the segment of the ECG from the start of the QRS complex to the end of the T wave, reflecting the full cycle of ventricular depolarization and repolarization. Corrected QT (QTc): normal <450 ms in men, <460 ms in women. A prolonged QT raises the risk of dangerous arrhythmias (ventricular tachycardia). A prolonged QT interval is associated with an "older" heart on ECG-AI analysis.

The number of red blood cells per liter — the carriers of hemoglobin

RBC (Red Blood Cell count) is the number of red blood cells that carry oxygen to tissues. Normal range: men 4.3–5.7 ×10¹²/L, women 3.8–5.1 ×10¹²/L. A decrease indicates anemia, bleeding or iron/B12/folate deficiency. An increase can occur with dehydration, erythrocytosis or hypoxia. In biological-age models (Bortz 2023) the red-cell count enters with a weak negative coefficient — a higher RBC correlates with a younger biological age.

A measure of red-cell size variability — higher under hematopoietic stress

RDW-CV (Red Cell Distribution Width — Coefficient of Variation) is a measure of the variability in red-cell size. Normal range: 11.5–14.5%. An elevated RDW reflects hematopoietic "stress": the appearance in the blood of young and old, large and small red cells. It rises with iron, B12 and folate deficiency and with chronic inflammation. It is a strong independent predictor of cardiovascular mortality and overall longevity — which is why it enters most blood-based biological-age models (PhenoAge, Bortz) with a positive coefficient.

The red blood cells that carry oxygen

Red blood cells (erythrocytes) contain hemoglobin and carry O₂ from the lungs to the tissues. In iron deficiency the red cells become small (microcytosis) and pale (hypochromia). Normal range: men 4.5–5.5 × 10¹²/L, women 3.8–5.1 × 10¹²/L.

An index of left-ventricular geometry — a marker of age-related heart remodeling

Relative wall thickness (RWT) is an index reflecting the geometry of the left ventricle. Formula: RWT = (2 × posterior wall thickness) / LV end-diastolic diameter. Normal: <0.42. RWT ≥ 0.42 is a sign of concentric remodeling or hypertrophy: the walls thicken disproportionately and the chamber shrinks. This geometry is typical of the aging heart under chronic arterial hypertension. In the RGNKTs study (2023) RWT ranked third among predictors of biological age (|ρ| ≈ 0.68).

The heart rate in a calm state

The resting heart rate is the number of heartbeats per minute in a calm state, best measured in the morning right after waking. In trained people it is lower (often 50–60 bpm) because the heart works more efficiently. A high resting heart rate is a marker of low fitness and increased load on the heart.

Unpleasant sensations in the legs at night

Restless legs syndrome (RLS, Willis–Ekbom disease) is a neurological disorder: unpleasant sensations in the legs (tingling, itching, pain) that compel movement, especially at rest and at night. Iron deficiency is found in 25% of RLS patients — a low ferritin (<50–75 ng/mL) is directly linked to the severity of symptoms.

Autoimmune inflammation of the joints

A chronic autoimmune disease in which the immune system attacks the joints, causing inflammation, pain and destruction of cartilage and bone tissue. Markers: rheumatoid factor (RF) and antibodies to cyclic citrullinated peptide (anti-CCP).

The transport protein for sex hormones — a marker of metabolic health

SHBG (Sex Hormone Binding Globulin) is a protein synthesized by the liver that binds testosterone and estradiol, regulating their free (biologically active) fraction. Normal range: men 18.3–54.1 nmol/L, women 32.4–128 nmol/L (of reproductive age). It falls with obesity, insulin resistance and hypothyroidism. It rises with hyperthyroidism, cirrhosis and in older people. Low SHBG is an independent predictor of type 2 diabetes and metabolic syndrome. In the Bortz Blood Age model log(SHBG) enters with a marked positive coefficient — in older people SHBG is usually elevated.

Muscle mass / height²

The Skeletal Muscle Index is skeletal-muscle mass relative to height squared (kg/m²). It is a key marker of muscular development and of sarcopenia diagnosis: low values (roughly <7.5 in men and <5.7 kg/m² in women) indicate a deficit of muscle mass.

Peripheral conversion of T4 → T3

SPINA-GD (Structure Parameter Inference Approach — the sum activity of peripheral deiodinases) is the calculated total activity of the deiodinases (in nmol/s) that convert storage T4 into active T3 in the tissues. Normal range 20–40 nmol/s. A decrease indicates impaired conversion (nutrient deficiency, inflammation, stress).

The gland's maximum thyroxine output

SPINA-GT (Structure Parameter Inference Approach — the thyroid's secretory capacity) is the calculated maximum secretory capacity of the thyroid gland (in pmol/s), based on TSH and free T4. Unlike isolated hormone levels, it reflects the gland's true functional capacity. Normal range 1.4–8.7 pmol/s; a decrease indicates hypothyroidism, an increase hyperthyroidism.

Age-related loss of muscle mass and strength

A progressive loss of muscle mass, strength and function associated with aging and low activity. It raises the risk of falls, disability and metabolic disorders. It can combine with excess fat (sarcopenic obesity), which is especially unfavorable.

A protein complex — the "guardian" of telomeres

Shelterin is a complex of six proteins (TRF1, TRF2, POT1, TIN2, TPP1, RAP1) that forms a protective "cap" on the ends of telomeres. It prevents the DNA-repair system from recognizing telomeres as damage, regulates telomerase access and maintains the loop (t-loop) structure of telomeres. Defects in shelterin cause telomeropathies.

Holding a small amount of data for a few seconds

The ability to hold a limited amount of information briefly (seconds to tens of seconds) without active processing — as opposed to working memory, where the information is also transformed. Its capacity is limited (classically "7±2" items). Transfer to long-term memory requires attention and repetition.

A family of proteins that regulate cellular stress and aging

Sirtuins (SIRT1–SIRT7) are enzymes that regulate the cell's stress response, DNA repair, inflammation and metabolism. They are activated by calorie restriction and exercise and depend on the coenzyme NAD+. Some of the protective effects of fasting and of certain supplements (resveratrol) are attributed to them, though there is not yet convincing evidence of lifespan extension in humans.

The mass of skeletal muscle

The estimated mass of skeletal muscle — the part of fat-free mass responsible for movement and, to a large extent, for metabolism. It declines with age (sarcopenia), especially without strength training. It is normalized to height as the skeletal muscle index (SMI).

BMI adjusted for age and sex, on a 0–70 point scale

The Smart Body Mass Index (SBMI) differs from ordinary BMI in three ways: it accounts for age and sex (not just weight and height), it is expressed as a comparative score on a 0–70 scale, and it directly shows the level of risk — the risk zones are always 10 points wide out of 70. The ideal range is 30–39 points. The scale was calibrated against risk curves, which differ for men and women: women tolerate weight deviations more easily. The current version is SBMI 2.7 (2019).

A class of drugs that lower LDL cholesterol by 30–55% — the cornerstone of heart-attack and stroke prevention.

Statins (atorvastatin, rosuvastatin, simvastatin) block the enzyme HMG-CoA reductase in the liver, reducing cholesterol synthesis. Effect: a 30–55% drop in LDL, a moderate reduction in triglycerides and a rise in HDL. High-intensity therapy (atorvastatin 40–80 mg, rosuvastatin 20–40 mg) lowers LDL by ≥50%. They are prescribed at a 10-year cardiovascular risk of ≥7.5% under the ACC/AHA 2013 guidance.

Fatty liver with inflammation

Steatohepatitis is the accumulation of fat in the liver accompanied by intralobular inflammation, ballooning degeneration of hepatocytes and possible development of fibrosis. It is a more severe stage than simple steatosis; it can be alcoholic or non-alcoholic (NASH).

Fatty hepatitis — inflammation on the background of steatosis

A stage of fatty liver disease with added inflammation and hepatocyte damage. It can progress to liver fibrosis and cirrhosis. It requires active treatment.

Fatty degeneration of the liver

The initial stage of fatty liver disease — the accumulation of neutral fats (triglycerides) in liver cells to more than 5% of the organ's mass. It is a reversible condition with lifestyle change.

Immature cells with the potential to turn into any type of body tissue

Stem cells are undifferentiated cells capable of self-renewal and of differentiating into specialized cells (muscle, nerve, blood and others). With age the pool of stem cells is depleted and their function deteriorates — one of the key mechanisms of aging. Stem-cell function is assessed in some extended biological-age tests as a marker of the body's regenerative potential. Aerobic exercise and periodic fasting stimulate the activation of stem cells.

An acute disruption of cerebral blood flow: ischemic (thrombosis) or hemorrhagic (vessel rupture).

Ischemic stroke (~87% of cases) is the blockage of a cerebral artery by a thrombus or embolus. Hemorrhagic stroke is a vessel rupture with bleeding into the brain. Symptoms (FAST): Face — facial asymmetry, Arm — arm weakness, Speech — speech impairment, Time — call emergency services immediately. "Time is brain": about 2 million neurons die every minute. Key risk factors: arterial hypertension, atrial fibrillation, atherosclerosis and smoking.

Early shifts in function without overt symptoms

Subclinical (preclinical) disorders of thyroid function are early deviations in which the values have already shifted but there are no vivid symptoms yet, and some tests formally remain within normal limits. Such states respond well to correction and are important for early diagnosis.

Adipose tissue beneath the skin

Adipose tissue located directly beneath the skin (it can be pinched). It serves as an energy store and thermal insulation. It is metabolically less active and less dangerous than the visceral fat around the organs.

The upper number in a blood-pressure reading — the pressure at the moment the heart contracts. Normal: 90–119 mmHg.

Systolic pressure reflects the maximum pressure of blood on the vessel walls at the moment of cardiac ejection. Normal: <120 mmHg. Elevated: 120–129. Stage 1 hypertension: 130–139. Stage 2 hypertension: ≥140. Isolated systolic hypertension (a high upper value with a normal lower one) is a common cause of stroke in older people. In the ACC/AHA equations, systolic pressure is one of the most significant risk factors.

Total iron-binding capacity of the serum

TIBC (Total Iron-Binding Capacity) is the maximum amount of iron that transferrin in the plasma can bind. Normal range: 250–370 µg/dL. In iron deficiency, TIBC rises (>370): the body synthesizes more transferrin to "capture" every iron atom. In iron overload or inflammation, it falls.

"Thin outside, fat inside"

TOFI (thin outside, fat inside) is a condition in which weight and BMI are normal but the fat fraction — especially visceral fat — is elevated. The metabolic and cardiovascular risks are almost the same as in overt obesity, because it is visceral fat that is dangerous, not the number on the scale.

The pituitary hormone that controls the thyroid gland

Thyroid-stimulating hormone (TSH) is produced by the pituitary and stimulates the thyroid gland. It is the most sensitive screening measure: in hypothyroidism TSH rises before T4 falls, so diagnosis begins with it. It is better interpreted by optimal ranges rather than reference ranges alone.

The adequacy of TSH to the free-T4 level

The Thyroid Sensitivity Index (Jostel) = ln(TSH) + 0.1345·fT4[pmol/L]. It reflects the pituitary's sensitivity to negative feedback from thyroid hormones and detects subtle disturbances of the hypothalamic-pituitary-thyroid axis that are not apparent from TSH and free T4 alone. Normal range 1.35–3.71.

The enzyme that restores telomere length

Telomerase is a ribonucleoprotein enzyme containing the catalytic subunit TERT and the RNA template TERC. It extends the telomeric repeats (TTAGGG) at the ends of chromosomes, compensating for their shortening during division. It is active in stem and germ cells. Most adult somatic cells do not express telomerase. It is reactivated in ~90% of cancer cells, granting them "immortality."

The protective "caps" at the ends of chromosomes — a marker of cellular aging

Telomeres are the terminal regions of chromosomes that protect them from degradation. They shorten with each cell division. Telomere length (kilobases per chromosome) is a direct marker of biological aging at the cellular level. Short telomeres are associated with an increased risk of age-related diseases.

Hereditary diseases caused by defective telomeres

Telomeropathies are a group of hereditary diseases caused by mutations in the genes of the telomere complex (TERT, TERC, DKC1, shelterin). They manifest as premature telomere shortening and impaired tissue regeneration. They include dyskeratosis congenita, idiopathic pulmonary fibrosis, aplastic anemia and liver cirrhosis. The severity of symptoms correlates with the degree of telomere shortening.

Five independent dimensions of personality

A scientific model of personality built from five independent traits: Openness to experience, Conscientiousness, Extraversion, Agreeableness and Neuroticism — hence the acronym OCEAN. It supports the idea that personality is better described by a set of independent dimensions than by a single number. A multidimensional profile of "mental age" is built on this logic.

The formation of a thrombus (blood clot) inside a vessel, disrupting blood flow.

Thrombosis is the pathological clotting of blood inside a blood vessel with the formation of a thrombus. It can develop in arteries (arterial thrombosis → heart attack, ischemic stroke) or veins (deep vein thrombosis, pulmonary embolism). The classic risk factors are Virchow's triad: vessel-wall damage, slowed blood flow and hypercoagulability. Elevated homocysteine strengthens all three components: it damages the endothelium, activates platelets and suppresses anticoagulant mechanisms. Test marker: D-dimer.

The endocrine organ that governs metabolism

The thyroid gland is a small, butterfly-shaped organ on the front of the neck. It produces the hormones T4 and T3, which regulate metabolic rate, heat production and the work of the heart, brain and many systems. A failure of its function affects the whole body.

A marker of autoimmune damage to the thyroid gland

Antibodies to thyroid peroxidase (anti-TPO) and to thyroglobulin (anti-TG) indicate an autoimmune attack on the thyroid gland. Their elevation is the main sign of autoimmune (Hashimoto's) thyroiditis, the most common cause of hypothyroidism.

How many calories the body spends per day, accounting for activity

TDEE (Total Daily Energy Expenditure) is the total energy spent over a day: the basal metabolic rate (BMR) multiplied by a physical-activity factor, plus the energy spent on movement and digesting food. TDEE is used as a reference when setting a diet's calorie level for weight loss, maintenance or gain.

The combined concentration of blood-plasma proteins

Total protein is the combined concentration of all blood-plasma proteins, primarily albumin and globulins. It reflects protein metabolism and the state of the liver, kidneys and nutrition. The normal range is usually about 64–83 g/L. It is used together with albumin to calculate globulins (total protein − albumin).

The iron-transport protein of the blood

Transferrin is a glycoprotein that carries iron ions (Fe³⁺) in the blood to the cells that use them: erythroblasts, hepatocytes and immune cells. Transferrin saturation <16% = iron deficiency. Total iron-binding capacity (TIBC) rises in iron deficiency.

The proportion of transferrin loaded with iron

Transferrin saturation is the percentage of transferrin bound to iron. It is calculated as: serum iron / TIBC × 100%. Normal range: 20–50%. <16% is a firm sign of functional iron deficiency. <10% is marked deficiency. >50% may indicate iron overload or impaired iron utilization.

The main type of fats in the blood — an energy store

Triglycerides are the main form of fat in the blood and in adipose tissue. An increase (≥ 1.7 mmol/L) is a component of metabolic syndrome and a cardiovascular risk factor, closely linked to insulin resistance and an excess of fast carbohydrates and alcohol.

Persistently high sugar due to insulin resistance and a relative lack of insulin

Type 2 diabetes mellitus is a disturbance of carbohydrate metabolism caused mainly by insulin resistance and a relative insulin deficiency (or a predominant impairment of insulin secretion). Criteria: fasting glucose ≥7.0 mmol/L or HbA1c ≥6.5% (confirmed). It develops gradually and can remain undiagnosed for years. Without control it raises the risk of cardiovascular disease and damage to the kidneys, nerves and retina.

A British biobank cohort of 500,000 people — the largest resource for biomedical research

UK Biobank is the United Kingdom's national biomedical database and research resource, combining genetic, biochemical, medical and lifestyle information on ~500,000 participants aged 40–69, recruited in 2006–2010. It includes ~60 blood biomarkers, genotyping, MRI scans and medical records. It has become the basis for hundreds of biological-age studies, including the Bortz Blood Age model (n=306,116, 2023).

Inflammation of the colon with bleeding

Ulcerative colitis is a chronic inflammatory disease of the colon with ulceration of the mucosa. It is accompanied by blood loss and impaired iron absorption. Iron-deficiency anemia occurs in 60–80% of patients. It requires regular monitoring of hemoglobin and ferritin.

The end product of protein breakdown — a marker of kidney function and protein metabolism

Urea is the main nitrogen-containing product of protein catabolism, synthesized in the liver and excreted by the kidneys. Normal range: 2.5–8.3 mmol/L. It rises with kidney failure, dehydration, a high-protein diet and gastrointestinal bleeding. It falls with liver disease, a low-protein diet and pregnancy. In the Bortz Blood Age model urea has a small negative coefficient.

A product of purine breakdown; in excess it causes gout and metabolic risk

Uric acid is the end product of purine metabolism, excreted by the kidneys. An elevated level (hyperuricemia) is linked to gout, as well as to metabolic syndrome, hypertension and kidney disease.

Maximal oxygen uptake — a measure of aerobic fitness

VO₂max (maximal oxygen uptake) is the largest volume of oxygen the body can take up per minute at peak exertion, in mL/kg/min. It is the gold standard for assessing cardiorespiratory fitness. It is measured precisely in the laboratory but can be estimated from indirect data (resting heart rate, activity level). A high VO₂max is linked to lower mortality risk.

The age of your vessels from risk factors and endothelial function

An estimated measure of the cardiovascular system's state: the age that corresponds to your vascular risk compared with a healthy person of the same sex without additional risk factors. If your real age is 45 but your vascular age is 54, your vessels work like those of a healthy 54-year-old — that is, your cardiovascular risk is higher than age alone would suggest. Unlike passport age, vascular age can be lowered by acting on reversible factors.

The arteries' ability to stretch and return to shape

The property of the arterial wall to stretch during systole and return to its original shape during diastole, smoothing the pulse wave. With age and with risk factors (blood pressure, sugar, smoking) the vessels become stiffer, which increases the load on the heart and the risk of cardiovascular disease. Reduced elasticity is one of the signs of "aged" vessels.

Fat around the internal organs

Adipose tissue that surrounds the organs of the abdominal cavity. Unlike subcutaneous fat, it is metabolically active: it releases pro-inflammatory molecules, raises insulin resistance and increases cardiovascular risk. It is one of the key manageable drivers of biological aging.

A water-soluble vitamin for DNA synthesis, nervous-system function and blood formation. It is stored in the liver, with reserves lasting 3–5 years.

B12 deficiency impairs blood formation (megaloblastic anemia) and the myelin sheath of nerves. Causes: veganism, atrophic gastritis, metformin use and malabsorption syndrome. Active B12 (holotranscobalamin) is the earliest marker of deficiency, detecting it before symptoms appear.

An antioxidant for collagen synthesis, immune defense and iron absorption. It is not synthesized in the body.

Subclinical deficiency, without overt scurvy, shows as fatigue, bleeding gums and slow wound healing. Smoking sharply increases the requirement. It enhances the absorption of non-heme iron.

A prohormone: calcium absorption, bones, muscles, immunity

Vitamin D (measured in the blood as 25(OH)D) is essentially a prohormone: without it, dietary calcium is barely absorbed in the intestine. It affects bone mineral density, muscle function and immunity. Deficiency is below 20 ng/mL (50 nmol/L), insufficiency 20–30 ng/mL, and the target level is 30–60 ng/mL. Deficiency is very common at northern latitudes, especially in autumn and winter.

The total number of white blood cells — an indicator of immune activity

WBC (White Blood Cell count) is the total number of leukocytes, which provide immune defense. Normal range: 4.0–9.0 ×10⁹/L. An increase (leukocytosis) occurs with infection, inflammation, leukemia and stress. A decrease (leukopenia) occurs with viral infections, autoimmune disease and chemotherapy. In the Levine PhenoAge model an elevated white-cell count reflects chronic inflammation and is linked to accelerated biological aging.

The ratio of waist to hip circumference

The waist-to-hip ratio is the ratio of waist circumference to hip circumference. It reflects the pattern of fat distribution (android "apple" or gynoid "pear") rather than the total amount. The WHO uses WHR as an indicator of cardiometabolic risk: normal is ≤0.90 in men and ≤0.80 in women; higher values are linked to an increased risk of heart disease and type 2 diabetes.

A marker of abdominal (visceral) obesity

Waist circumference measured at the midpoint between the lowest rib and the iliac crest (the WHO protocol). It is a simple and strong indicator of visceral fat and metabolic risk. Elevated values are linked to accelerated aging, diabetes and cardiovascular disease.

The ratio of waist circumference to height

WHtR (waist-to-height ratio) = waist circumference / height. It is a simple marker of abdominal (visceral) obesity: a value below 0.5 is considered favorable, while above 0.5–0.6 indicates increased cardiometabolic risk. It is more sensitive than BMI to fat distribution.

A temporary rise in BP at a medical facility due to stress

A temporary rise in blood pressure (by more than 20/10 mmHg) at a medical facility because of the stress associated with visiting a doctor. It is the opposite of masked hypertension: the pressure is high "at the doctor's" but normal in everyday life. To distinguish them, home measurements and 24-hour monitoring are used.

The brain's "notepad" for holding information here and now

A system for briefly holding and actively processing information over seconds — for example, to keep a confirmation code in mind or do mental arithmetic. It is closely linked to attention and fluid intelligence. A decline in working memory is often one of the first noticeable signs of cognitive aging.

A trace element for more than 300 enzymes: immunity, wound healing, DNA synthesis, taste and smell.

The body does not store zinc, so a daily dietary intake is essential. Deficiency → reduced immunity, hair loss and impaired healing. It is assessed by fasting plasma zinc levels.

Probability of a cardiovascular event (heart attack, stroke) within the next 5 years

The estimated probability, expressed as a percentage, of developing cardiovascular disease or an event (myocardial infarction, stroke) within the next 5 years. It is calculated from a combination of risk factors: sex, age, blood pressure, cholesterol, glucose, kidney function, smoking and diabetes. It is useful for comparison against threshold levels (low / moderate / high / very high) and for tracking change over time as lifestyle or treatment changes.

A protein marker of liver fibrogenesis activity

α2-macroglobulin is a large plasma protein and protease inhibitor. It reflects the activity of fibrogenesis (scar-tissue formation) and rises as liver fibrosis progresses, which is why it is one of the key components of the FibroTest.