Are modifiable risk factors for dementia really modifiable?

PURPOSE OF REVIEW: The 2024 Lancet Commission estimates 45% of dementias worldwide are preventable if 14 potentially modifiable risk factors for dementia were eliminated. While this is unlikely, there is evidence that even modest risk factor reduction will have significant benefits. Whether this is best achieved at the level of the individual or broader population level approaches is the purpose of this review. RECENT FINDINGS: To date, evidence for the efficacy of individual-level interventions in preventing cognitive decline or dementia is modest at best. Reasons for this include the sociodemographic and risk profile of study participants and complex disease causes, while overlooking the underlying social and commercial determinants of health influencing risk exposure. There is, however, growing evidence supporting population-level approaches to dementia risk reduction. Trend studies from high-income countries showing declines in dementia incidence over recent decades suggest their effectiveness. SUMMARY: The limited evidence for the efficacy, let alone effectiveness, of individual-level interventions is in part because they operate within the influence of social and commercial determinants of health. For significant and sustained risk factor reduction, population-level interventions targeting the underlying determinants of risk factor exposure across the life course, with sensitivity to diverse contexts, are required.