The non-linear link between remnant cholesterol and diabetic retinopathy: a cross-sectional study in patients with type 2 diabetic mellitus

OBJECTIVE: Research on residual cholesterol (RC) and diabetic retinopathy (DR) remains limited. As a result, the current study was designed to investigate the relationship between RC and DR in patients with type 2 diabetic mellitus (T2DM). METHODS: This cross-sectional study consecutively and non-selectively collected a total of 1964 type 2 diabetic mellitus patients in two hospitals in Taiwan from April 2002 to November 2004. A binary logistic regression model was then used to assess the independent relationship between RC level and DR and proliferative diabetic retinopathy (PDR). A generalized additive model (GAM) and smooth curve fitting were used to investigate the actual shape of the curve between them. It was stated that the data had been uploaded to the website:https://journals.plos.org/plosone. RESULTS: The average age of the participants was 64.10+/− 11.32 years old, with 42.92% being male. The prevalence of DR and PDR was 35.13 and 18.13%, respectively. The mean RC level was 30.57 ± 14.60 mg/dL. We found no significant association between RC and DR (OR = 1.001; 95% CI 0.991, 1.011) or PDR (OR = 1.008; 95% CI 0.995, 1.021) based on a fully adjusted logistic regression model. Results remained robust across a series of sensitivity analyses. However, a non-linear relationship was detected between RC and DR. Using a two-piece logistic regression model and a recursive algorithm, we found an inflection point of RC was 13.0 mg/dL. A 1-unit increase in the RC level was associated with 19.4% greater adjusted odds of DR (OR = 1.194; 95% CI 1.070, 1.333) when RC < 13.0 mg/dL. There was also a non-linear relationship between RC and PDR, and the inflection point of the RC was 39.0 mg/dL. When RC < 39.0 mg/dL, a 1-unit increase in the RC level was associated with 2.1% greater adjusted odds of PDR (OR = 1.021; 95% CI 1.004, 1.038). CONCLUSION: This study demonstrates a non-linear relationship between RC and DR or PDR in type 2 diabetic mellitus patients. Our findings provide new insights into advancing research on the link between RC and DR or PDR. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12902-022-01239-5.