Trends and cross-country inequalities in the global burden of Alzheimer’s disease and other dementias among adults aged 65+ years, 1990–2021: a population based study with projections into 2050

Background: Alzheimer's disease and other dementias (ADOD) pose a significant global health challenge, with projected annual increases. The growing elderly population exacerbates burdens, underscoring the need for interventions. Methods: Using data from the Global Burden of Disease Study 2021, we analysed global ADOD trends from 1990 to 2021 among adults aged 65+ and projected to 2050. Average annual percentage change (AAPC) in the age-standardised prevalence, mortality and disability-adjusted life years (DALYs) rates of ADOD were calculated to quantify the temporal trends. Results: Globally, the number of adults aged 65 years or older living with ADOD increased from 18.1 (95% uncertainty interval [UI] 14.4-22.5) million in 1990 to 49.1 (38.7-61.3) million in 2021 (AAPC 0.09%). While mortality rates remained relatively stable (AAPC 0%), DALYs increased by 176% (AAPC 0.02%). Females consistently exhibited a higher age-standardised prevalence (7,603 [95% UI 6,023-9,469] cases per 100,000 population) vs. 5,744 [4,486-7,205]) and mortality (304 [78 to 782] vs. 225 [54-626]) rate compared to males, with notable regional variations. From 1990 to 2021, the age-standardised prevalence of ADOD increased only in East Asia and High-income Asia Pacific (AAPC 0.79% and 0.16%). High fasting plasma glucose, high body-mass index, and smoking were identified as primary risk factors. Projections indicate a 50.1% increase in age-standardised prevalence by 2050, with an estimated 191 (52-330) million cases, and a predicted death toll of 6.8 (2.4-11.3) million. Conclusion: The global number of people living with dementia nearly tripled from 1990 to 2021, mainly due to increases in population ageing and growth. The findings emphasize the need for comprehensive strategies to address ADOD, including prevention, early diagnosis, and effective management, with a focus on gender and regional disparities.