Early-onset type 2 diabetes: the next major diabetes transition.

The incidence of early-onset type 2 diabetes is increasing, with a growing number of cases now occurring in children, adolescents, and young adults. This transition is primarily driven by the rising prevalence of obesity in younger populations, especially in high-income countries. However, the relationship between obesity and early-onset type 2 diabetes varies across ethnic groups, with some populations exhibiting a higher risk at lower BMI thresholds, possibly due to differences in insulin resistance and β-cell function. Socioeconomic factors further shape disease patterns, with early-onset type 2 diabetes disproportionately affecting lower-income populations in high-income settings, whereas in low-income and middle-income countries, economic development and urbanisation have contributed to increasing incidence among more affluent groups. The consequences of this transition to early-onset type 2 diabetes are severe, with accelerated disease progression, heightened risks of microvascular and macrovascular complications, and considerable societal and health-care burdens compared with later-onset disease. Given the continuing rise in childhood and adolescent obesity, the incidence of early-onset type 2 diabetes is expected to increase further, placing mounting pressure on health-care systems worldwide. In the first of three papers in this Series, we examine global trends in the incidence and prevalence of early-onset type 2 diabetes, identify key drivers of this transition to diagnosis at younger ages, and review the evidence for risk factors both at population and individual level.