Associations between diabetic retinopathy and systemic complications in patients with type 2 diabetes mellitus: a retrospective cross-sectional analysis of the PHDA diabetes complications data set in China

To investigate the associations between diabetic retinopathy (DR) and selected systemic complications in patients with type 2 diabetes mellitus (T2DM). This retrospective cross-sectional study analyzed data from the National Population Health Science Data Center’s PHDA Diabetes Complications Data Set in China. The dataset included 3,000 patients with T2DM collected between January 1, 2018, and December 31, 2022, comprising 1,500 patients with DR and 1,500 without DR. Clinical characteristics and systemic complications were compared between groups. Estimated glomerular filtration rate (eGFR) was calculated from age, sex, and serum creatinine. Multivariable logistic regression evaluated associations between DR and complications after adjustment for age, sex, fasting blood glucose, and HbA1c. No missing values were identified. Patients with DR had higher HbA1c, blood pressure, serum creatinine, and blood urea levels and lower eGFR than those without DR (78.95 ± 33.89 vs. 93.05 ± 22.93 mL/min/1.73 m², p < 0.001). Diabetic nephropathy (60.07% vs. 24.93%), chronic kidney disease (10.60% vs. 1.60%), and lower extremity artery disease (23.73% vs. 7.93%) were more frequent in the DR group (all p < 0.001). DR was significantly associated with lower extremity artery disease (OR 3.914, 95% CI 3.012–5.086), diabetic nephropathy (OR 1.952, 95% CI 1.590–2.397), and chronic kidney disease (OR 2.131, 95% CI 1.257–3.613). An inverse association was observed between DR and coronary heart disease (OR 0.507, 95% CI 0.415–0.620). In this predefined 1:1 analytic sample of patients with T2DM, DR was associated with renal and lower-extremity vascular complications. These findings should be interpreted cautiously given the cross-sectional design, predefined sampling structure, and unavailable important confounders.