The Dementia Prevention Study That Proves 40% of Cases Are Avoidable

A major Lancet Commission update found 40% of dementia cases are preventable through 14 modifiable risk factors. Here is what those factors are and what you should be doing now.

The Lancet Commission on Dementia Prevention, Intervention, and Care — whose initial 2017 report estimated that 35 percent of dementia cases were attributable to modifiable risk factors — updated its analysis in 2024 with two additional risk factors added to the model and new data on existing ones. The updated estimate: approximately 40 percent of dementia cases are potentially preventable through addressing modifiable risk factors across the lifespan.

The 14 modifiable risk factors the Commission identifies, spanning three life stages: in early life (education — higher educational attainment is associated with greater 'cognitive reserve' that delays dementia symptom emergence); in midlife (hearing loss, hypertension, obesity, alcohol consumption above recommended limits, traumatic brain injury, air pollution exposure); and in late life (smoking, depression, physical inactivity, social isolation, diabetes, and — the two newly added — untreated vision loss and elevated LDL cholesterol).

The population attributable fraction of each risk factor — the proportion of dementia cases that would be eliminated if that risk factor were completely eliminated — varies. Hearing loss has the largest single-factor population attributable fraction at approximately 8 percent, reflecting both its high prevalence and its specific mechanism: hearing difficulty reduces cognitive stimulation and social engagement in ways that accelerate cognitive decline. Physical inactivity is second at approximately 4 percent.

For practical prevention: the specific interventions with the best evidence for each factor are manageable. Hearing aids for hearing loss (dramatically underused despite evidence of cognitive benefit). Blood pressure management (a standard hypertension treatment that reduces dementia risk by approximately 35 percent in people with hypertension). Physical activity (the aerobic exercise BDNF effects discussed earlier specifically protect hippocampal volume). Social engagement maintenance (the mechanism likely overlaps with the loneliness research — isolation promotes neuroinflammation that accelerates cognitive decline).

For the screening implication: the Commission recommends that people assess their dementia risk factor status beginning in midlife — specifically, addressing hearing loss, blood pressure, and blood sugar in the 40s and 50s, when the prevention window is most open and the interventions have decades of effect ahead of them.