Can lifestyle really prevent dementia?

Reducing risk yes, preventing no — and the difference is not pedantry. The 2024 report of the Lancet Commission names 14 modifiable risk factors, among them high blood pressure, hearing loss, smoking, physical inactivity, diabetes and social isolation. The Commission estimates what share of dementia cases could arithmetically be avoided if those factors were eliminated across the whole population. That is a sound statement about a population. It permits no statement about whether a particular person prevents their dementia through particular measures. Addressing the factors is still worthwhile, not least because the same factors simultaneously lower cardiovascular risk.

That depends on what you expect from the result. Blood-based markers such as pTau217 measure reliably and are increasingly used in diagnosis in people with symptoms. For someone without symptoms the situation differs: an abnormal value currently triggers no treatment that demonstrably changes the course. It can be a considerable burden without anything following from it. That is precisely why this procedure sits at evidence tier 3 here and is documented rather than used to guide action. With a family cluster and early onset, genetic counselling may be the more sensible route, with proper information and the explicit right not to know a result.

The factors with the best data are unspectacular and overlap heavily with cardiovascular prevention: blood pressure in the target range, physical activity, not smoking, treating hearing loss, controlling glucose metabolism, social participation. That is the honest core. What that list does not contain is supplements, brain-training programmes with efficacy claims, or individual biomarkers from which a treatment could be derived. Anyone tracking these factors measurably lowers their cardiovascular risk and plausibly their dementia risk — with the difference that the former is evidenced in randomised trials.