Association analysis and exploratory mediation study of the stress-induced hyperglycaemia ratio and glycaemic ratio indices with diabetic retinopathy in patients with type 2 diabetes

Objective: Diabetic retinopathy (DR) is a major microvascular complication of type 2 diabetes mellitus (T2DM), and traditional glycaemic control indicators struggle to comprehensively predict its risk. This study aims to investigate the association between the stress hyperglycaemia ratio (SHR), fasting blood glucose/glycated hemoglobin (FBG/HbA1c), postprandial 2-h glucose/glycated hemoglobin (P2hBG/HbA1c) with DR in T2DM patients, and the mediating effects of non-high-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio (NHHR) and triglycerides/high-density lipoprotein cholesterol ratio (TG/HDL-C). Methods: This study is a retrospective cross-sectional study based on inpatients at a single center. A total of 1,924 T2DM patients were enrolled and grouped according to DR status and quartiles of SHR, FBG/HbA1c, and P2hBG/HbA1c. Multivariate logistic regression, subgroup analysis, restricted cubic spline (RCS) analysis, and mediation effect analysis were employed to validate the associations between indicators and their underlying mechanisms. Results: The DR group exhibited a considerably higher proportion of participants in the upper quartiles for SHR, FBG/HbA1c and P2hBG/HbA1c. In the fully adjusted model (Model 4), the following comparisons were made between the Q1 quartile and the Q2, Q3 and Q4 quartiles: Q2 (OR = 1.65, 95% CI: 1.24-2.21), Q3 (OR = 1.75, 95% CI: 1.31-2.33) and Q4 (OR = 2.51, 95% CI: 1.88-3.36). For FBG/HbA1c, the following comparisons were made between Q2 (OR = 1.42, 95% CI: 1.06-1.91), Q3 (OR = 1.85, 95% CI: 1.39-2.48) and Q4 (OR = 2.95, 95% CI: 2.21-3.94). For P2hBG/HbA1c, the fourth quartile (OR = 1.56, 95% CI: 1.17-2.08). Subgroup analysis and RCS analysis confirmed a consistent linear association across all subgroups, with no significant non-linearity. The present study demonstrated that NHHR and TG/HDL-C exhibited significant independent mediating effects in the association between these glycaemic markers and DR. Conclusion: The present study found a positive correlation between SHR, FBG/HbA1c and P2hBG/HbA1c with the prevalence of DR in T2DM patients. Furthermore, NHHR and TG/HDL-C exhibited exploratory mediating effects in these associations.