Global burden of Alzheimer's disease and other dementias during 1990-2021: a Global Burden of Disease and Risk Factors Study 2021-based study

Introduction: In most countries and territories, current data on the burden of Alzheimer's disease (AD) and other dementias are lacking. We aimed to assess the trends, burden, and inequalities of AD and other dementias at global, regional, and national level from 1990 to 2021. Methods: The data on disease burden of AD and other dementias during 1990-2021 were extracted from Global Burden of Disease and Risk Factors Study 2021 (GBD 2021). Average annual percentage changes (AAPCs) of age-standardized prevalence, mortality, and disability adjusted life years (DALYs) were estimated as an indicator to evaluate the healthcare system. Result: The global age-standardized prevalence of AD and other dementias increased from 672 (95% uncertainty interval: 589 to 764) per 100,000 population in 1990 to 694 (603 to 794) per 100,000 population in 2021, with AAPCs of 0.09% (95% confidence interval: 0.06% to 0.11%). However, age-standardized mortality did not change (AAPCs: 0.00% (−0.01% to 0.02%)) and age-standardized DALYs slightly increased from 446 (206 to 958) to 451 (213 to 950) per 100,000 population (AAPCs: 0.01% (0.00% to 0.03%). While the highest prevalence remained in population aged 65-69 and the countries with a high-middle socio-demographic index (SDI) such as East Asia (e.g., China), the highest mortality and DALYs were found in population aged 65-69 and the countries with a low-middle SDI such as South Asia (e.g., India). High fasting plasma glucose ranked the highest risk factor for DALYs during 1990-2021. Conclusion: The global increased prevalence of AD and other dementias may partly be attributed to population aged 65-69 in the countries with a high-middle SDI (e.g., China), whereas mortality and DALY ratio of population aged 65-69 from the countries with a low-middle SDI (e.g., India) is the most significantly growing. Controlling of high fasting plasma glucose may be needed for the reduction of DALYs from AD and other dementias.