Dementia is not a single disease but a syndrome: a lasting decline in memory, thinking, speech and the ability to plan, severe enough to interfere with daily life and independence. It goes beyond ordinary age-related forgetfulness.
Most often dementia is caused by Alzheimer’s disease. It is frequently preceded by a milder stage — mild cognitive impairment.
What dementia is and its types
Dementia is an umbrella term for a lasting decline in cognitive function due to damage or death of nerve cells. The main types are: Alzheimer’s disease (about 60–70% of cases), vascular dementia (after strokes and chronic damage to the brain’s vessels), dementia with Lewy bodies, and frontotemporal dementia. A mixed form — a combination of several causes — is common.
Dementia and aging: where the line is
With age, processing speed and memory can decline a little — this is normal and does not interfere with independent living. In dementia the impairment progresses and affects everyday life: a person gets lost in familiar places, forgets recent events, and cannot manage finances or medications. The intermediate state, when the decline is already detectable on testing but independence is preserved, is called mild cognitive impairment.
Modifiable risk factors
The main risk factor is age, and it cannot be changed. But the Lancet Commission (2024) identified 14 modifiable factors that are linked to about 45% of dementia cases worldwide: low education, hearing and vision loss, hypertension, high LDL cholesterol, obesity, smoking, depression, physical inactivity, diabetes, excess alcohol, traumatic brain injury, social isolation and air pollution. Elevated homocysteine is separately linked to the risk.
What you can do
There is no prevention with a 100% guarantee, but reducing the factors listed genuinely lowers the risk. What works: controlling blood pressure, blood sugar and cholesterol, correcting hearing with hearing aids, regular aerobic activity (which raises BDNF), mental and social activity, quitting smoking, and preventing stroke.
Calculate using this marker
Calculators where Dementia is used directly:
Frequently asked questions
Are dementia and Alzheimer’s disease the same thing?
No. Dementia is a syndrome (a set of symptoms), while Alzheimer’s disease is the most common but not the only cause of it. There is also vascular and frontotemporal dementia, dementia with Lewy bodies, and mixed forms.
Can dementia be prevented?
There is no full guarantee, but about 45% of cases worldwide are linked to modifiable factors. Controlling blood pressure, blood sugar, cholesterol and hearing, physical and mental activity, and quitting smoking all lower the risk.
Related terms
Sources
- Alzheimer’s Association — What Is Dementia?
- Replicating the 2024 Lancet Commission Model (PMC)
- Broadening dementia risk models: 2024 Lancet Commission (PubMed)