Trends, inequalities, and cross-location similarities in global dementia burden and attributable risk factors across 204 countries and territories: a systematic analysis for the Global Burden of Disease Study 2021

Abstract

Background: The latest global burden of dementia, its risk factors, and demographic and social inequalities remain unclear, yet are crucial for shaping health policies.

Materials and methods: We conducted a systematic analysis using data from the 2021 Global Burden of Disease Study to estimate global dementia prevalence, deaths, and disability-adjusted life years (DALYs) for that year and analyzed trends since 1990. We identified regions with similar changes in disease burden patterns, assessed risk factors and their trends, and examined disparities related to sex, age, sociodemographic index (SDI), and universal health coverage (UHC).

Results: In 2021, dementia accounted for 56.9 million global cases, 2.0 million deaths, and 36.3 million DALYs. Global age-standardized rates per 100 000 population were: prevalence 694 (95% uncertainty intervals: 602.9-794.1), deaths 25.2 (6.7-64.2), and DALYs 451 (212.7-950.2), with increases of 3.2%, 0.5%, and 1.2% since 1990, respectively. In 2021, East Asia had the highest regional age-standardized prevalence (887.9), led nationally by China (900.8), Lebanon (828.3), and Germany (820.5). Central Sub-Saharan Africa reported the highest regional age-standardized death rates (34.9), particularly in the Democratic Republic of the Congo and Gabon (35.4 each) and Congo (34.5). For age-standardized DALYs, Central Sub-Saharan Africa was highest regionally (591.4), led by the Democratic Republic of the Congo (600.2), Gabon (588.3), and Afghanistan (577.7). We identified four regional and six national clusters based on prevalence and DALY trends. Women experienced higher prevalence, deaths, and DALYs across all regions and countries. Globally in 2021, high fasting plasma glucose (FPG) (14.6% of age-standardized dementia DALYs, + 39.5% since 1990, leading in 20 regions and 193 countries, impacting males more), high body-mass index (BMI) (7.1%, + 53.3%, leading in 1 region and 11 countries, impacting females more), and smoking (4.1%, -22.3%, impacting males more) were the main contributors. Across the life course, below the age of 55, high BMI was the main risk for females; below 65, smoking for males; above these ages, high FPG for both sexes. SDI slightly increased DALYs, while UHC significantly reduced them.

Discussion: The global dementia burden has slightly increased but remains substantial, with significant regional and sex disparities. Poor-performing clusters should adopt strategies from better ones. Prevention programs must target modifiable risk factors - high FPG, BMI, and smoking - using sex- and age-specific approaches. Strengthening UHC is essential to alleviate the growing dementia burden.

Keywords: Alzheimer’s disease; dementia; disease burden; risk factor; universal health coverage.