Age and diabetic complications in type 2 diabetes: the role of disease duration and stage-dependent effects

Background: Diabetic complications represent a major source of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). However, the role of age in the development and progression of complications across different stages remains incompletely understood. Methods: This cross-sectional study included 489 patients with T2DM. Diabetic complications were classified as macrovascular disease (MaVD), microvascular disease (MVD), and peripheral neuropathy (PN). The number of complications (0, 1, 2, ≥3) was used to assess complication burden. Logistic regression, partial proportional odds models, interaction analysis, and restricted cubic spline (RCS) models were applied to evaluate the association between age and diabetic complications. Results: The overall prevalence of complications was 75.66% and increased progressively with age. Age was independently associated with the presence of diabetic complications after adjustment for confounders (OR = 1.06, 95% CI: 1.03-1.08). The effect of age was more pronounced during the transition from no complications to multiple complications, but attenuated at higher stages. Subtype analysis showed that age was most consistently associated with microvascular disease, while the association with peripheral neuropathy was borderline and not significant for macrovascular disease after full adjustment. A significant interaction between age and diabetes duration was observed, indicating that the effect of age was stronger in early-stage disease but diminished with longer duration. RCS analysis demonstrated a positive and approximately linear association between age and complication risk. Conclusions: Age is independently associated with diabetic complications in T2DM, particularly in the early and intermediate stages of complication development. The effect of age varies by complication subtype and is modified by diabetes duration.