Trends and Disparities in the Impact of Diabetes Mellitus Mortality and Disability, 1990–2021: A Systematic Analysis of the 2021 Global Burden of Disease Study

The global burden of diabetes is influenced by population size, age structure, disease prevalence, and disease severity. However, systematic analyses of diabetes severity remain limited. This study estimated global trends and disparities in diabetes severity across sociodemographic index (SDI) levels using Global Burden of Disease 2021 data. Age-standardized mortality-to-prevalence ratio (MPR) and disability-adjusted life years-to-prevalence ratio (DPR) were used as proxies for severity. A higher MPR indicates greater case fatality, whereas a higher DPR reflects heavier per-case burden of disability and premature death. The slope index of inequality and relative index of inequality were used to measure disparities across SDI levels, and average annual percentage changes (AAPCs) were computed to quantify temporal trends. Globally, the age-standardized MPR decreased from 0.57% in 1990 to 0.32% in 2021 (AAPC = -1.81%, P <0.001), and DPR decreased from 20.62 to 14.86% (AAPC = -1.03%, P <0.001). Eastern Sub-Saharan Africa (e.g., Malawi) had the highest diabetes severity, whereas Eastern Europe (e.g., Russian Federation) exhibited increasing trends. SDI exhibited a near-linear negative correlation with diabetes severity. Although absolute disparities in diabetes severity between high- and low-SDI countries declined from 1990 to 2021, relative disparities increased. Type 1 diabetes was more severe than type 2 in individuals younger than 60 years, particularly in children under 5 years. This pattern reversed in older adults, with higher type 2 severity. Overall, although global diabetes severity declined from 1990 to 2021, disparities persist across regions, countries, age groups, and diabetes types.