Trends in PCOS Incidence, Prevalence, and DALYs Across Five BRICS Nations, 1990–2050: A Decomposition, Age-Period-Cohort, and Bayesian Forecasting Analysis Based on GBD 2021

Objective: Polycystic ovary syndrome (PCOS) burden has risen globally, yet comparative analyses across BRICS nations (Brazil, Russia, India, China, South Africa)-representing 40% of the global population under rapid epidemiological transition-remain limited. This study aimed to assess PCOS burden in BRICS from 1990 to 2021, compare with global trends, and project outcomes to 2050 using decomposition, age-period-cohort (APC), and Bayesian methods. Methods: Using Global Burden of Disease Study 2021 (GBD 2021) data restricted to females, we analyzed age-standardized incidence, prevalence, and disability-adjusted life year (DALY) rates (ASIR, ASPR, ASDR) with 95% uncertainty intervals (UIs). Das Gupta decomposition partitioned changes into population growth, ageing, and epidemiological change. APC modeling assessed temporal trends, and Bayesian APC (BAPC) forecasting projected burden to 2050. Estimated annual percentage changes (EAPCs) were calculated with 95% confidence intervals (CIs). Results: From 1990 to 2021, global incident cases rose by 55.9% and prevalent cases by 89.6%, with global ASIR, ASPR, and ASDR increasing 27-28%. BRICS burden remained below global averages but showed significant upward trends. China and India had the fastest growth (EAPC for DALYs: 2.01 [1.99-2.03] and 2.06 [2.03-2.08]) versus the global average (0.81 [0.80-0.82]). Decomposition showed epidemiological change dominated in China (68-78%) and Russia (92-138%), whereas population growth predominated in Brazil (79-98%) and South Africa (66-69%). APC analysis identified the highest burden in ages 20-44, with rising period and cohort risks except in Brazil. BAPC projects global ASDR to increase from 15.46 to 20.20 per 100,000 by 2050. China shows the largest rise (13.38 to 21.39), surpassing the global level around 2045, followed by India (12.24 to 14.53). The 10-29 age group will contribute most future cases. Conclusion: Rising PCOS burden in BRICS, especially China and India, is driven by heterogeneous factors: epidemiological changes (China, Russia) versus population growth (Brazil, South Africa). Negative net drift in age-specific rates coexists with rising total burden, reconcilable via decomposition. These findings imply targeted strategies: lifestyle interventions for China/Russia, healthcare capacity expansion for Brazil/South Africa, integrated approaches for India, and adolescent-focused prevention across all BRICS.