Insulin resistance correlates with maculopathy and severity of retinopathy in young adults with Type 1 Diabetes Mellitus

Aims: To assess the relationship between insulin resistance (IR), retinopathy and maculopathy in young adults with Type 1 diabetes mellitus. Methods: A cross-sectional study at a regional Australian tertiary hospital. Retinal pathology, assessed by colour fundus photography, was correlated with two surrogate measures of IR: estimated Glucose Disposal Rate (eGDR) and Insulin Sensitivity Score (ISS), where lower scores reflect greater IR. Results: 107 patients were recruited, with mean age 24.7 years, 53% male, and mean duration of disease 10.8 years. Mean eGDR scores (5.6 vs 8.0 p < 0.001) and ISS (4.7 vs 7.9, p < 0.001) were lower in subjects having at least moderate non-proliferative diabetic retinopathy (NPDR; relative to nil/mild-NPDR). Similarly, mean eGDR (4.2 vs 6.2, p = 0.001) and ISS (3.8 vs 6.1, p = 0.003) were lower in patients with maculopathy. Multivariate logistic regression modelling was used to control for confounding. For retinopathy severity, a unit increase in eGDR or ISS (representing lower IR) was associated with a 50% decrease in odds of moderate-NPDR or worse (eGDR OR 0.5, 95%CI 0.32–0.77, p = 0.002; ISS OR 0.49, 95%CI 0.29–0.84, p = 0.01). A unit increase in eGDR or ISS was associated with a 46–56% decrease in odds of maculopathy (eGDR OR 0.54, 95%CI 0.37–0.81, p = 0.003; ISS OR 0.44, 95%CI 0.22–0.88, p = 0.02). Conclusions: IR correlates with more severe retinopathy in young adults with Type 1 DM. This is the first description of a correlation between IR and maculopathy in Type 1 DM, warranting further evaluation. Prospective studies examining whether reducing IR can improve microvascular complications are required.