Type 2 diabetes in BRICS countries from 1990 to 2023: burden, trends and complementary Mendelian randomization evidence.

BACKGROUND: The burden of type 2 diabetes (T2D) is increasing across BRICS countries, but cross-national comparative evidence on recent trends and drivers is limited. METHODS: Using Global Burden of Disease (GBD) 2023 data, we analyzed T2D-related deaths, years of life lost (YLLs), years lived with disability (YLDs) and disability-adjusted life years (DALYs) from 1990 to 2023 in Brazil, Russia, India, China and South Africa. Age-standardized rates, estimated annual percentage changes, joinpoint trends, decomposition of changes in absolute burden, and Bayesian age-period-cohort projections were evaluated. Attributable burden was assessed using the GBD comparative risk assessment framework. As a secondary analysis, two-sample Mendelian randomization (MR) was performed for selected exposures using external GWAS datasets of predominantly European ancestry, without using the MR estimates to explain between-country differences or to validate the GBD attribution. RESULTS: In 2023, India had the largest absolute burden of type 2 diabetes, whereas South Africa had the highest age-standardized DALY and mortality rates. China ranked second in absolute burden but lowest in age-standardized rates. From 1990 to 2023, age-standardized DALY rates increased in all five countries, with the steepest increases in India and the Russian Federation. Epidemiological change drove burden increases in India and Russia, population ageing in China, and population growth in Brazil and South Africa. High fasting plasma glucose and high BMI accounted for the largest attributable DALY fractions. In complementary MR analyses, adiposity, several glycemic traits, smoking initiation, and television viewing time showed positive primary-analysis associations with T2D, although these provide etiological context rather than BRICS-specific causal estimates. CONCLUSIONS: T2D burden in BRICS countries is high, heterogeneous, and still increasing, highlighting the need for country-specific prevention and care strategies.