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

Abstract

AbstractBackgroundForty percent of dementia cases could potentially be prevented through modifiable risk factors. However, the effect of risk factor reductions might be partially offset by individuals living longer and developing dementia later. Using a microsimulation model, we determined the effect of reductions in smoking and hypertension prevalence on the future dementia burden.MethodThe microsimulation model ‘MISCAN‐Dementia’ was used to simulate life histories and dementia development of 10 million individuals. We modelled mid‐life (40‐59 years) hypertension and late‐life (65+ years) smoking as risk factors (Figure 1), simulating four risk groups: (1) neither risk factor, (2) smoking only, (3) hypertension only, and (4) both risk factors. Sex‐specific population data were used to determine risk factor prevalence. Based on prior literature, smoking and hypertension were each set to a 1.6‐fold increase in dementia risk, and a loss of life expectancy of 4 and 2 years, respectively. Reductions in risk factor prevalence of 100% (i.e. elimination), 50%, 25% and 10% were modeled and evaluated in terms of life years (LYs) without dementia gained, LYs with dementia averted and incident dementia cases averted.ResultCompared to no reduction, for the lifetime of 1000 individuals, elimination of hypertension results in 360 LYs without dementia gained, 40 LYs with dementia averted and 4 incident cases averted. Although smoking elimination results in 600 LYs without dementia gained, it also causes 75 more dementia LYs and 10 more incident cases. These additional LYs with dementia occur primarily at older ages, due to relatively high life expectancy gains compared to moderate reductions in dementia risk (Figure 2). Reductions of 50%, 25% and 10% result in similar findings at lower magnitudes.ConclusionReductions in prevalence of hypertension and smoking result in a gain in life years free of dementia. However, for smoking this coincides with a (smaller) increase in life years with dementia at older ages. These findings suggest that treatment or prevention of dementia risk factors will generally result in a larger number of cognitively healthy life years, but potentially at the cost of minor increases in years with dementia for risk factors with large effects on survival.