Supplementary Material for: Global Trends and Disparities in Early-Onset Dementia: Systematic Analysis and Projection from the Global Burden of Diseases 2021 Study

Background: Early-onset dementia (EOD) is an escalating health concern with profound consequences for individuals and health systems. Clarifying its burden is crucial for guiding resources, advancing diagnosis and interventions, and shaping health policies. Objective: To assess the global EOD burden based on the Global Burden of Diseases (GBD) 2021 Study. Methods: We analyzed the incidence, prevalence, disability-adjusted life years (DALYs), and deaths from EOD of people aged 40–64 years, estimating age-standardized rates and average annual percentage change (AAPC) from 1990 to 2021. The Bayesian age-period-cohort (BAPC) model was utilized to project incidence from 2022 to 2030. Results: From 1990 to 2021, EOD cases more than doubled globally, increasing in incidence from 0.64 to 1.38 million and in prevalence from 3.68 to 7.76 million. The global age-standardized incidence rate rose slightly from 61.22 to 64.74 per 100,000 (AAPC=0.17%), with parallel increases in prevalence (AAPC=0.09%), DALYs (AAPC=0.08%), and deaths (AAPC=0.07%). In 2021, East Asia and Tropical Latin America exhibited the highest incidence (>80/100,000); while high-income North America, East Asia, and Tropical Latin America exhibited the highest prevalence and DALY rates. The highest incidence and prevalence were in high-middle sociodemographic index (SDI) regions, while DALYs and deaths were greatest in middle SDI regions. Females generally had a higher EOD burden than males. Projections indicate minor fluctuations in age-standardized incidence rates to 2030. Conclusion: The global burden of EOD has increased due to population growth and aging, despite a relatively stable age-standardized incidence. Notable disparities were observed across sex, SDI levels, regions, and countries. Addressing this growing challenge will require strategic policy-making and the judicious allocation of resources, tailored to the specific contexts and needs of different regions.