Here is the single most useful number in dementia prevention: the 2024 Lancet Commission estimates that about 45% of dementia cases are tied to 14 modifiable risk factors across life. It is a population-level estimate, not a personal guarantee, but it reframes the picture from waiting and worrying to doing something concrete.
“Modifiable” describes population risk, not a promise to an individual; our APOE4 risk primer puts that distinction in context. The US POINTER review is the deeper evidence check, and the exercise guide offers one concrete starting protocol.
The factors are not all equal. The largest in the model are hearing loss, high LDL cholesterol (low-density lipoprotein, whose particles can deposit cholesterol in artery walls), and less education, followed by smoking, depression, social isolation, physical inactivity, diabetes, high blood pressure, obesity, excess alcohol, traumatic brain injury, air pollution, and (added in 2024) vision loss. For carriers, the highest-leverage and best-evidenced are exercise, blood pressure, lipids, and metabolic health.
Your genotype is only one input. You cannot change it, but you can act on the factors around it, and the payoff is bigger the earlier you start, while interventions have decades to compound. None of this promises prevention, and how much any one person can shift their own risk is genuinely uncertain. But the direction is encouraging. Start with the levers you control, or go straight to the highest-leverage one, exercise.