Incidence of and risk factors for cataract among diabetes clinic attenders

Abstract

The incidence of and risk factors for cataract during a mean (standard deviation (SD)) follow-up period of 5.0 (3.0) (range 0.1-12.4) years were examined among 3606 patients (2001 male and 1605 female) with diabetes mellitus from three outpatient clinics at the University Hospital, Nottingham. Among the 3606 patients free of cataract at initial registration who attended the clinic at least twice in the period 1979-1992, the mean (SD) age was 49.2 (17.8) years with a mean (SD) duration of diabetes of 7.6 (9.8) years at initial registration. The incidence of cataract was 10.4 (95% confidence interval (CI), 9.0, 11.9) per 1000 person-years based on 18089 person-years of follow-up. The incidence for females (13.6 (95% CI, 11.0, 16.1)) was greater than in males (8 (95% CI, 6.3, 9. 7)) (P<0.001). The incidence of cataract in insulin-dependent diabetes mellitus (IDDM), non-insulin-treated and insulin-treated non-insulin-dependent diabetes mellitus (NIDDM) were 7.1 (95% CI, 5. 4, 8.9), 11.7 (95% CI, 9.1, 14.3) and 17.8 (95% CI, 12.9, 22.7) per 1000 person-years, respectively. Age-adjustment substantially changed the ordering of risk associated with different types of diabetes. Using a Cox's Proportional Hazards Model for IDDM and NIDDM (insulin and non-insulin-treated) diabetes separately, age and any retinopathy were significant independent predictors of cataract for all groups. Poor metabolic control also was a significant independent predictor of cataract for the IDDM and insulin-treated NIDDM diabetes groups. Duration of diabetes was a significant independent predictor of cataract for the IDDM group. Age at diagnosis of diabetes, systolic and diastolic blood pressure, body mass index, proteinuria, cigarette smoking and creatinine had no significant independent association with cataract when other covariates were considered. These findings will help the identification of those diabetic patients at particular risk of cataract so that clinic time for screening of eyes can be appropriately focused and health care planning for people with diabetes considered.