Could Country-Level Factors Explain Sex Differences in Dementia Incidence and Prevalence? A Systematic Review and Meta-Analysis

Background: Despite rising interest in sex differences in dementia, it is unclear whether sex differences in dementia incidence and prevalence are apparent globally. Objective: We examine sex differences in incidence and prevalence of Alzheimer’s disease (AD), Vascular dementia (VaD), and Any dementia and evaluate whether country-level indicators of gender inequality accounted for differences. Methods: Systematic review with meta-analysis was used to obtain estimates of incidence and prevalence of AD, VaD, and Any dementia using random effects meta-analysis, and population-based studies with clinical or validated dementia measures. Meta-regression was used to evaluate how country-specific factors of life-expectancy, education, and gender differences in development, unemployment, and inequality indices influenced estimates. Results: We identified 205 eligible studies from 8,731 articles, representing 998,187 participants across 43 countries. There was no sex difference in incidence of Any dementia, AD, or VaD, except in the 90 + age-group (women higher). When examined by 5-year age bands, the only sex difference in prevalence of Any dementia was in the 85+, and there was no sex difference in VaD. AD was more prevalent in women at most ages. Globally, the overall prevalence of dementia in adults 65 + was higher for women (80.22/100, CI:62.83-97.61) than men (54.86/1000 CI:43.55-66.17). Meta-regression revealed that sex differences in Any dementia prevalence, were associated with gender differences in life expectancy and in education. Conclusion: Globally, there are no sex differences in age-specific dementia incidence, but prevalence of AD is higher in women. Country-level factors like life expectancy and gender differences in education may explain variability in sex differences.