Global, Regional, and National Disparities in the Burden of Alzheimer's Disease and Other Dementias, 1990–2021

Background: Driven by population ageing, the burden of Alzheimer’s disease and other dementias (ADOD) continues to rise. A comprehensive assessment of the ADOD burden at global, regional, and national levels is critical for public health. Methods: Based on Global Burden of Disease Study 2021, we assessed the ADOD burden. Temporal trends were analysed using Joinpoint regression; inequalities among countries were evaluated via Lorenz curves; and future trends were projected employing an age-period-cohort model. Results: In 2021, the age-standardised rates for ADOD were 694.01 (95% uncertainty intervals [UI]: 602.88 to 794.08) for prevalence, 119.76 (95% UI: 104.96 to 135.89) for incidence, and 481.70 (95% UI: 228.79 to 1023.96) for disability-adjusted life years (DALYs). Females exhibited a higher ADOD burden than males across all age groups, with an age-standardised prevalence rate of 769.94 (95% UI: 670.71–877.57) in females compared to 589.47 (95% UI: 507.48–678.79) in males. The slope inequality index of crude DALY rate increased from 315.23 (95% CI: 310.43 to 437.87) in 1990 to 758.29 (95% CI: 692.48 to 908.29) in 2021 at the country level. The Lorenz curves for the crude DALY rate of ADOD in 1990 and 2021 lay below the equality line, indicating a higher burden among countries and territories with higher socio-demographic index (SDI) ranking. By 2046, global prevalence is projected to reach 124.89 million, a 119.67% increase from 2021. Conclusion: The ADOD burden has increased globally, with significant regional disparities. Urgent action is required to prevent ADOD, especially among females and in high-SDI regions.