Familial clustering of diabetic retinopathy in South Indian type 2 diabetic patients

Abstract

Aim: The aim of the study was to determine whether there is familialclustering of diabetic retinopathy among South Indian Type 2 diabeticsubjects. Methods: During the period September 1991 to September 1997, 322 families withat least two diabetic siblings who were registered at our centreand had undergone a retinal examination were selected for the study.The sibling with the longest duration of diabetes was defined as theproband. The prevalence of retinopathy was compared between thesiblings of probands with and without retinopathy. Results: Diabetic retinopathy was diagnosed in 11.2% of the siblingsof the probands without diabetic retinopathy and in 35.3% ofthe siblings of the probands with diabetic retinopathy (P < 0.0001). Theincreased prevalence of retinopathy among siblings of probands withretinopathy represented all grades of retinopathy, namely non-proliferativediabetic retinopathy with and without maculopathy and proliferative diabeticretinopathy, although the latter did not reach statistical significancedue to the small numbers. Hypertension, metabolic control and theduration of diabetes among the probands did not affect the clusteringof retinopathy. The odds ratio for retinopathy in the siblings of probandswith retinopathy after adjusting for age, glycosylated haemoglobin, durationof diabetes, proteinuria and other confounding variables was 3.37(95% confidence interval 1.56-7.29, P = 0.002). Conclusions: Familial clustering of diabetic retinopathy was three times higherin siblings of Type 2 diabetic subjects with diabetic retinopathy.