Global trends in the prevalence of type 2 diabetes mellitus: understanding trajectories through conceptual frameworks

BACKGROUND: Type 2 diabetes mellitus (T2DM) is imposing a substantial and rapidly growing global health burden. Disease estimates vary widely across geographies and time periods, reflecting not only true differences in disease occurrence but also variation in demographic structures, risk factor exposures, diagnostic practices, surveillance capacity, and biological heterogeneity within T2DM itself. METHODS: A narrative, integrative synthesis of global epidemiological evidence was conducted. Data were sourced from major international platforms, supplemented with peer-reviewed literature. Evidence was synthesized across time, place, and person, with explicit attention to differences in case definitions, biomarker use, screening intensity, and modeling assumptions. Conceptual frameworks were applied to interpret observed patterns. RESULTS: Harmonized NCD-RisC analyses show a sustained rise in age-standardized prevalence from 1980 to 2014, increasing from 4.3% to 9.0% in men and from 5.0% to 7.9% in women. According to the IDF, the global burden is projected to reach 852.5 million by 2050. Approximately 42.8% (251.7 million) of cases remain undiagnosed, with the highest proportions concentrated in low-income regions. Substantial geographic heterogeneity is shaped by population aging, rising adiposity, dietary and physical activity transitions, urbanization, commercial food environments, and health system detection capacity. Subtype distribution and biological heterogeneity further contribute to variation in disease trajectories and complication profiles across populations. CONCLUSIONS: Global T2DM prevalence reflects the interaction of biological, social, and health system processes rather than incidence alone. Prevalence trajectories must be interpreted in light of surveillance limitations, diagnostic context, and within-disease heterogeneity. Addressing future burden requires combining improved detection and chronic-care capacity with upstream, life-course-oriented prevention strategies.