Global, regional, and national burden of Alzheimer's disease and other dementias from 1990 to 2021: findings from the Global Burden of Disease Study 2021.

Background: As the global population continues to age, the growing number of elderly individuals has contributed to an increase in age-related conditions and illnesses, such as dementia, which places considerable financial and emotional pressure on both families and society. Alzheimer's disease (AD), the most prevalent form of dementia among the elderly, significantly impacts their quality of life and ability to perform daily activities independently. Over the past three decades, the age-standardized mortality rate has declined and life expectancy has steadily increased worldwide. However, this long-term progress was disrupted by the COVID-19 pandemic, which reversed some of the gains made in life expectancy and contributed to a global decline. The pandemic has notably affected global health, exacerbating the prevalence of Alzheimer's disease and other dementias (ADOD). Methods: In line with the analytical approach used in the Global Burden of Disease Study (GBD) 2021, we examined the counts and age-standardized rates (ASR) for the prevalence, incidence, mortality, and Disability-Adjusted Life Years (DALYs) associated with ADOD, categorized by region, country, sex, and age from 1990 to 2021. To assess temporal patterns over the study period, we calculated the estimated annual percentage changes (EAPCs). Results: From 1990 to 2021, both the number and age-standardized rates (ASR) of prevalence, incidence, mortality, and DALYs associated with ADOD showed a significant increase globally. Regionally, high-middle SDI regions had the highest ASPR at 766.2 per 100,000 (95% UI: 659.8, 879.6), with the most considerable rise, reflected in an EAPC of 0.21 (95% CI: 0.17, 0.25). In East Asia, the highest age-standardized incidence rate (ASIR) was reported, at 149.6 (95% UI: 129.6, 171.1) per 100,000 people, along with the greatest increase in ASIR, at 0.4 (95% UI: 0.33, 0.47) among the 21 GBD regions. On a national level, China experienced the greatest burden of ADOD, with the highest ASPR of 900.8 (95% UI: 770.9, 1043.2) and the highest ASIR of 151.5 (95% UI: 131.2, 173.3) per 100,000 people. The 80-84 age group exhibited the highest rates of prevalence, incidence, and DALYs, whereas the number of deaths in the 85-89 age group surpassed those in other age categories. Throughout all age groups, females experienced a higher burden of ADOD than males, regardless of the time or geographical location. The burden of ADOD reached its lowest point in 2019 but has increased steadily since then. Conclusion: In summary, this study highlights the global epidemiological trends of ADOD from 1990 to 2021, including the impact of the COVID-19 pandemic on it. As the population ages, ADOD has emerged as a significant public health concern worldwide. Although some regions have made progress in managing the burden of ADOD, most regions and countries still face a heavy disease burden. More effective prevention and treatment strategies are needed to alleviate the impact of ADOD. In particular, greater focus should be placed on women and the elderly.