The non-linear association between remnant cholesterol/high-density lipoprotein cholesterol ratio and diabetic retinopathy: a cross-sectional study in type 2 diabetic patients

Abstract Objective The strong correlation between the ratio of residual cholesterol to high-density lipoprotein cholesterol (RC/HDL-c) and major cardiovascular events has been extensively studied. However, the role of this ratio in diabetic retinopathy (DR) has not been investigated. Hence, this present study aims to examine the association between the RC/HDL-c ratio and DR in patients diagnosed with type 2 diabetes mellitus (T2DM). Methods This study conducted a cross-sectional analysis involving a total of 1942 patients diagnosed with T2DM in two Taiwanese hospitals, spanning from April 2002 to November 2004. The primary objective was to explore the independent association between the RC/HDL-c ratio and the presence of DR, as well as proliferative diabetic retinopathy (PDR), using a binary logistic regression model. To accurately determine the shape of the association between these variables, we utilized a generalized additive model (GAM) and employed smooth curve fitting techniques. The data was downloaded from the website: https://journals.plos.org/plosone . Results Our study comprised participants with an average age of 64.06 ± 11.32 years, with males accounting for 43.05% of the total. Among the patients, 35.12% were found to have DR, while PDR was present in 18.23% of cases. The average RC/HDL-c ratio was calculated as 0.67 ± 0.39. Utilizing a fully adjusted logistic regression model, we investigated the potential association between the TC/HDL-c ratio and both DR and PDR. However, no statistically significant association was observed (DR: OR 1.060; 95% CI 0.707, 1.588; PDR: OR 1.258; 95% CI 0.773, 2.047). Interestingly, we did discover a non-linear association between the RC/HDL-c ratio and DR. Employing a two-piece logistic regression model and a recursive algorithm, we identified an inflection point at 0.460. When the RC/HDL-c ratio fell below 0.460, each 1-unit increase in the ratio was associated with an 11.8-fold increase in the adjusted odds of developing DR (OR = 12.824; 95% CI 3.583, 45.897). Moreover, a non-linear association between the RC/HDL-c ratio and PDR was observed, with an inflection point occurring at 0.90. When the RC/HDL-c ratio was below 0.90, a one-unit increase in the ratio was linked to a 1.46-fold increase in the adjusted odds of PDR (OR = 2.459; 95% CI: 1.245, 4.857). Conclusion This study contributes valuable insights into the intricate association between the RC/HDL-c ratio and both DR and PDR in individuals diagnosed with T2DM. By identifying a non-linear association, our findings enhance the existing knowledge surrounding the link between the RC/HDL-c ratio and the development of DR and PDR.