Severe microvascular disease incidence over a 34-year period among Chinese with newly diagnosed diabetes and impaired glucose tolerance: the Da Qing diabetes outcome study 1986–2020

AIMS: The aim of this study was to investigate the incidence of severe microvascular disease in adults with newly diagnosed diabetes (NDD), impaired glucose tolerance (IGT) and normal glucose tolerance (NGT) over a 34-year follow-up in China. METHODS: This cohort study enrolled 1631 individuals, including 598 NDD, 540 IGT and 493 NGT initially identified in 1986, who were followed until death, loss to follow-up, or December 31, 2020. Severe microvascular disease was defined as a composite outcome of severe retinopathy, nephropathy, and neuropathy. RESULTS: During the 34-year follow-up, 85.18% (460/540) of the IGT population progressed to diabetes, while 34.89% (172/493) of the NGT subjects developed diabetes. By 2020, severe microvascular disease occurred in 65.03% (95% CI: 58.90%-70.48%) of individuals with NDD, 32.90% (95% CI: 28.19%-37.81%) with IGT, and 16.18% (95% CI: 12.64%-20.11%) with NGT. A comparable trend was observed for the cumulative incidence of each individual microvascular complication component across the three groups. The incidence rate per 1000 person-years was 21.7 in the NDD group, which was higher than that in the IGT (9.7) and NGT (4.4) groups. After adjustment for confounders, the risk of severe microvascular disease was 6.3-fold higher in the NDD group (95% CI: 4.65-8.38, P < 0.0001), and 2.2-fold higher in the IGT group (95% CI: 1.58-2.95, P < 0.001) compared with the NGT group. CONCLUSIONS: NDD and IGT in Chinese adults were associated with markedly elevated long-term risk of severe microvascular complications. These findings underscore the importance of achieving optimal glycemic control early in the course of diabetes and implementing intensive lifestyle intervention in IGT to slow or prevent progression to diabetes.