The impact of modifiable risk factor reduction on future dementia burden: a microsimulation modeling study

Approximately 30%-50% of dementia cases are attributable to modifiable risk factors, but the impact of risk reduction strategies on dementia incidence at a population level is uncertain. Reliable estimates of intervention effects require accounting for changes in life expectancy when intervening on risk factors, and model realistic reduction scenarios that consider co-occurrence of risk factors. Using the microsimulation model MISCAN-Dementia, we assessed the effect of interventions on mid-life hypertension and late-life smoking on dementia and mortality risk. We modeled risk factor reductions, from small reductions to complete elimination, and evaluated effects on dementia incidence and prevalence, number of cases, and life years with and without dementia. All risk factor reductions resulted in lower dementia incidence and prevalence, fewer dementia cases, and more dementia-free life years. Eliminating smoking resulted in 1.4% fewer dementia cases for women and 2.5% for men over their lifetime. Eliminating hypertension reduced dementia cases by 1.1% for women and 3.3% for men. The number of dementia cases and life years with dementia decreased until around age 90, after which a slight increase was observed due to prolonged life expectancy with the reductions. Reducing smoking and hypertension will result in additional life years without dementia and a modest reduction in overall dementia cases, with some additional dementia cases in the oldest old. These findings emphasize the potential of dementia risk reduction strategies and the importance of considering concurrent changes in mortality when evaluating risk factor reductions.