Incidence of and risk factors for diabetic retinopathy in diabetic clinic attenders

The incidence and risk factors for the development of diabetic retinopathy during a mean (SD) follow-up period of 4.6 (2.9) (range 1-12.4) years have been examined among 3424 patients (1878 males and 1546 females) with diabetes mellitus from three outpatient clinics at the University Hospital, Nottingham. The mean (SD) age of participants was 49.2 (17.9) years with a mean (SD) duration of diabetes of 7.3 (9.0) years at initial registration. Among the 3424 patients free of retinopathy at initial registration who attended the clinic at least twice in the period 1979-1992, the incidence of any retinopathy was 59.6 (57.8 male and 61.8 female) per 1000 person-years based on 15,571 person-years of follow-up. The incidence rate of retinopathy was 72% higher among insulin-treated than among non-insulin-treated noninsulin-dependent diabetes mellitus (NIDDM) clinic attenders. Using a Cox's Proportional Hazards Model for insulin-dependent diabetes (IDDM) and NIDDM (insulin and non-insulin-treated) diabetes separately, longer duration of diabetes, higher systolic blood pressure and poor metabolic control were significant independent predictors of retinopathy for all three groups. Never smoking was a significant independent predictor of retinopathy for the insulin-dependent diabetes groups. Lower body mass index, proteinuria and age were predictors of retinopathy only for non-insulin-treated NIDDM patients. Gender and creatinine had no significant independent association with retinopathy when other covariates were considered. These findings will help the identification of those patients at particular risk of retinopathy so that clinic time for screening of eyes can be appropriately focused.