The impact of coronary artery bypass grafting on the short‐ and long‐term development and progression of diabetic retinopathy: A Danish national matched cohort study

PURPOSE: Diabetic retinopathy (DR) is a frequent long-term complication of diabetes. While hemodynamic changes are known risk factors for DR, the effect of coronary artery bypass grafting (CABG) on the development of DR is poorly investigated. We aimed to examine the short- and long-term effects of CABG on DR development or progression in a national cohort. METHODS: This longitudinal, register-based matched cohort study included individuals with diabetes aged 18 years or older from the Danish Registry of Diabetic Retinopathy (DiaBase). We included individuals with and without CABG in a 1:2 match, based on sex, year of birth, type of diabetes and level of DR. We then evaluated the effect of CABG on short- (0-12 months) and long-term (above 24 months) development and progression of DR in adjusted Cox proportional hazard regression models. RESULTS: Among 3633 individuals in the two groups (median aged 68 years with 82.4% males), CABG was not associated with short-term development (hazard ratio (HR) 1.14, 95% confidence interval (CI) 0.71-1.82) or progression (HR 1.13, 95% CI 0.75-1.70) of DR. Nor did it result in long-term development (HR 1.06, 95% CI 0.76-1.49) or progression (HR 1.10, 95% CI 0.78-1.55) of DR. However, the individuals from the CABG group had a lower chance of long-term DR-regression (HR 0.56, 95% CI 0.38-0.83). CONCLUSION: Although CABG is associated with a 44% lower chance of long-term DR-improvement, it did not increase the short- or long-term risk of DR development or progression. Hence, we did not find evidence that individuals undergoing CABG should receive additional DR screening postoperatively.