Global trends in prevalence, disability adjusted life years, and risk factors for early onset dementia from 1990 to 2021.

This study aims to analyze temporal trends in the prevalence and disability-adjusted life year (DALY) burden of early-onset dementia (EOD) globally from 1990 to 2021 and assess the attributable burdens of modifiable risk factors. Data from the Global Burden of Disease Study (GBD) 2021 were used. EOD was defined as dementia in individuals aged 40-64. The analysis included case numbers, age-standardized prevalence rates (ASPRs), and DALY rates (ASDRs) with 95% confidence intervals (CIs), stratified by global, regional, and national levels, sociodemographic index (SDI), and sex. Joinpoint regression analysis evaluated the average annual percent change (AAPC). Population attributable fractions (PAFs) estimated the proportion of DALYs attributable to risk factors. The global number of EOD cases and DALYs nearly doubled from 1990 to 2021, reaching 7.758 million cases (95% CI 5.827-10.081) and 3.774 million DALYs (95% CI 1.696-8.881) in 2021. ASPR and ASDR increased slightly to 355.9 (95% CI 267.2-462.8) and 173.3 (95% CI 77.9-407.7) per 100,000 in 2021. In 2021, the highest ASPR was in high-middle SDI countries at 387.6 per 100,000 (95% CI 291.1-506.8), while the highest ASDR was in middle SDI at 182.9 per 100,000 (95% CI 82.2-431). The fastest ASDR increase was in low and low-middle SDI countries from 2010 to 2021, with AAPCs of 0.42% (95% CI 0.34-0.50) and 0.36% (95% CI 0.33-0.39), respectively. A significant negative correlation was found between SDI and ASDR. During the COVID-19 pandemic (2019-2021), ASPR and ASDR in high-SDI countries declined, while other SDI regions saw an accelerated increase. In 2021, high fasting plasma glucose (FPG) was the most significant attributable risk factor for EOD-related DALYs globally, with PAFs for high body mass index and high FPG increasing in nearly all regions since 1990, while the PAF for smoking decreased. In 2021, EOD burden was highest in high-middle and middle SDI countries, particularly rising during the COVID-19 pandemic. The growing influence of metabolic risk factors underscores the need for targeted public health policies and resource allocation to mitigate the EOD burden.