A comprehensive review and meta-analysis of relationship between age of onset or duration of type 2 diabetes and mortality involving more than 2.85 million patients

The association between age of onset or diabetes duration and all-cause mortality in individuals with type 2 diabetes (T2D) remains incompletely characterized. We aimed to clarify this relationship. On February 8, 2025, we searched CINAHL, Scopus, PubMed, Cochrane Central, Embase, and Web of Knowledge for observational studies and post-hoc or subanalyses of randomized controlled trials (p-h/sa of RCTs) assessing the relationship between age of onset or diabetes duration and all-cause mortality. We pooled relative risks (RRs) using a random-effects model and assessed heterogeneity with Cochran’s Q test and I² statistic. A leave-one-out sensitivity analysis confirmed the robustness of results. The protocol was not registered. Thirty-seven studies involving 2,857,346 participants were included. Earlier T2D onset was associated with higher all-cause mortality (pooled RR = 1.54; 95% CI: 1.03–2.32). When adjusting for current age, later onset correlated with lower mortality (pooled RR = 0.60; 95% CI: 0.44–0.83). Longer diabetes duration was linked to increased mortality (pooled RR = 1.43; 95% CI: 1.14–1.79), regardless of adjustment. Earlier-onset T2D is consistently associated with higher all-cause mortality, suggesting it may serve as an important risk marker, though causality is not established. Asymmetry in funnel plots and Egger’s tests suggests possible publication bias. Future well-designed studies should explore causal mechanisms to inform interventions.