Disproportionate microvascular burden emerging at younger ages in early- versus late-onset type 2 diabetes: an age-standardized analysis in Northern China

The age-comparable burden of complications in early-onset type 2 diabetes remains uncertain. We compared metabolic characteristics and age-standardized complication prevalence between early- and late-onset type 2 diabetes and examined factors associated with microvascular complications in early-onset disease. This retrospective cross-sectional study included 1,940 individuals hospitalized with type 2 diabetes in Northern China between 2018 and 2025: 1,116 diagnosed before 40 years of age and 824 diagnosed at 40 years or older. Group differences were assessed using independent-samples t, Mann–Whitney U, or chi-square tests. Complication prevalence was directly standardized to the 2020 China Population Census using four common age strata among individuals aged 40 years or older. Restricted cubic splines examined associations between age at diagnosis and complications. Nine prespecified covariates were entered simultaneously into a multivariable logistic regression model for microvascular complications in the early-onset group. Early-onset disease was characterized by poorer glycemic control, greater insulin resistance, adiposity, dyslipidemia, and higher serum uric acid. Although crude prevalences of atherosclerotic cardiovascular disease and diabetic peripheral neuropathy were lower in early-onset disease, age-standardized prevalences were higher for atherosclerotic cardiovascular disease (23.5% versus 19.0%; P = 0.049), diabetic nephropathy (32.5% versus 12.5%; P < 0.001), and diabetic retinopathy (28.0% versus 10.4%; P < 0.001). The difference in diabetic peripheral neuropathy was not significant (36.6% versus 33.2%; P = 0.188). Spline analyses showed nonlinear associations of age at diagnosis with atherosclerotic cardiovascular disease and diabetic peripheral neuropathy. In the prespecified model, younger age at diagnosis, longer diabetes duration, higher body mass index, higher glycated hemoglobin, and higher serum uric acid were independently associated with microvascular complications. Each 60-µmol/L increase in serum uric acid was associated with an adjusted odds ratio of 1.472 (95% confidence interval, 1.315–1.647). Early-onset type 2 diabetes was associated with a more adverse metabolic profile and higher age-standardized nephropathy and retinopathy burdens. Serum uric acid was independently associated with microvascular complications but should be considered only as a complementary clinical correlate pending prospective validation. These findings support earlier metabolic and microvascular assessment.