Global Distribution of Sex Differences in the Incidence and Prevalence of Any Dementia, Alzheimer's Disease, and Vascular Dementia: A Systematic Review and Meta-Analysis

Abstract

Background: We estimated global incidence of Alzheimer’s disease (AD), Vascular dementia (VaD), and Any dementia reported evaluated whether country level socio-demographic factors could explain variation in gender differences in dementia prevalence and incidence. Methods: We conducted a systematic review with meta-analysis to obtain estimates of incidence and prevalence of AD, VaD and Any dementia using random effects meta-analysis. We included population-based studies with clinical diagnoses or validated dementia screening instruments. We excluded studies lacking a valid clinical diagnoses, population-based sampling, or gender stratified estimates. We used meta-regression to evaluate how country specific factors of life-expectancy, education, and gender differences in development, unemployment and inequality indices influenced estimates. Findings: Our searches identified 205 eligible studies from 8731 articles, representing 998 187 participants across 43 countries. Global incidence (95% CI) of Any dementia/1000 person-years for men at age 60-64, 66-69, 70-74, 75-79, 80-84, 85-89 and 90+ was 2·5 (1·9-3·2), 5·1 (4·0-6·5). 10·1 (7·9-12·8), 19·7 (15·5-24·9), 34·0 (26·9, 43·0), 59·6 (47·3, 74·8), and 84·5 (67·5, 105·4) respectively. For women the corresponding figures were 1·8 (1·3-2·5), 3·4 (2·5-4·7), 9·1 (6·6-12·4), 23·7 (17·3-32·4), 46·44 (34·1, 62·9), 84·54 (62·8, 112·9), and 142·2 (107·4, 185·9). There was no difference in incident Any dementia, or for AD or VaD, or prevalence of Any dementia, in any age group except for the 90+, where it was higher in women. AD was more prevalent in women at most ages, and VaD was only more prevalent in men aged 65-69. Meta-regression revealed that gender differences in Any dementia prevalence, may be explained by the gender differences in life expectancy and education. Interpretation: Globally, there are no gender differences in dementia incidence except in the 90+ age-group. Greater focus on the role gender inequality and life expectancy play as a potential explanations of gender differences in dementia and AD prevalence is needed. Registration Details: The review was registered with the International Prospective Register of Systematic Reviews (PROSPERO, CRD42017053915) and reported in accordance with the PRISMA Statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Funding Information: ARC Laureate Fellowship FL190100011, National Health and Medical Research Council (NHMRC) Grants 1100579, 1102694. NHMRC Dementia Centre for Research Collaboration Declaration of Interests: The authors have no conflicts of interest.