What causes dementia?
Dementia happens when disease damages nerve cells in the brain so it can no longer work properly. Different diseases cause different types. In Alzheimer's, amyloid and tau proteins build up, and vascular dementia follows reduced blood flow. Age is the biggest risk factor, not a normal part of aging.
At the most basic level, the answer is simple: dementia is caused by damage to the brain. As the Alzheimer's Society explains, disease injures nerve cells, and as more cells are damaged the brain becomes less able to do its job. The symptoms depend on where the damage is and how fast it spreads.
Different diseases, different damage
Dementia is an outcome, not a single cause. Several diseases can produce it, each harming the brain in its own way:
- Alzheimer's disease involves a build-up of abnormal amyloid and tau proteins, which form plaques and tangles. It often affects memory regions like the hippocampus first, which is why forgetfulness tends to come early.
- Vascular dementia follows reduced blood flow to the brain, for example after a stroke.
- Lewy body and frontotemporal dementias are driven by other abnormal proteins affecting different regions.
What raises the risk
Age is the single biggest risk factor, but dementia is not an inevitable part of getting older. Family history plays a modest role for most people (see is dementia hereditary). Beyond that, the strongest influences are the ones that also affect heart health: high blood pressure, diabetes, smoking, physical inactivity, hearing loss, and social isolation. Major reviews suggest a meaningful share of dementia risk is linked to factors like these, which means some of it is within our influence even though none of it is guaranteed.
What it is not
Dementia is not caused by normal aging, and it is not a moral or personal failing. It is a set of physical diseases. If new confusion appears suddenly, that is more likely a treatable problem such as infection, medication, or delirium than dementia, and it is worth a prompt medical check.
This is general information, not medical advice. Every situation is different, so talk to a doctor about yours.