Long-term smoking and early-onset diabetic retinopathy in young-onset type 2 diabetes

BackgroundYoung-onset type 2 diabetes mellitus is associated with prolonged disease duration and early development of complications such as diabetic retinopathy. Smoking is a modifiable risk factor, but longitudinal evidence in this population remains limited.ObjectiveTo evaluate the association between long-term smoking and the risk of diabetic retinopathy, including earlier-occurring cases, in young-onset type 2 diabetes mellitus.MethodsThis retrospective cohort study used electronic medical records and a diabetic complication database from Pu'er People's Hospital, this retrospective cohort study included 488 patients aged 18-39 with type 2 diabetes (2023-2025) and no DR at baseline. Patients were followed from diabetes diagnosis until DR, last fundus exam, death, or June 30, 2025. Smoking status and cumulative exposure were assessed, and patients were followed until incident diabetic retinopathy or censoring. Kaplan-Meier analysis, Cox regression, restricted cubic splines, and sensitivity analyses were performed.ResultsDuring follow-up, 92 patients developed diabetic retinopathy, including 61 earlier-occurring cases. Smokers had a significantly higher cumulative incidence of diabetic retinopathy. Adjusted analyses showed that smoking was associated with increased risk of diabetic retinopathy (hazard ratio 1.78, 95% confidence interval 1.18-2.69) and earlier-occurring diabetic retinopathy (hazard ratio 1.92, 95% confidence interval 1.21-3.05). A nonlinear dose-response relationship was observed, with greater cumulative exposure associated with earlier onset.ConclusionLong-term smoking is associated with higher risk and earlier occurrence of diabetic retinopathy in young-onset type 2 diabetes mellitus, supporting early screening and smoking cessation strategies in this high-risk population.