Development of Proliferative Retinopathy in NIDDM: A Follow-up Study of American Indians in Oklahoma

To determine the incidence of and risk factors for the development of proliferative diabetic retinopathy (PDR) in Oklahoma Indians, we performed a cohort follow-up study of 927 Indians who underwent detailed eye examinations between 1972 and 1980. The mean age of participants was 52 yr with a duration of diabetes of 6.9 yr at baseline. At follow-up, 513 (55.3%) were alive, 407 (43.9%) were deceased, and 7 (0.8%) could not be traced. After a mean follow-up time of 12.7 yr, the overall incidence of PDR among those who survived and who underwent follow-up ophthalmic examinations (354 participants) was 18.6%; 45% of those with background retinopathy at baseline developed PDR. Significant independent predictors of PDR, determined by muKivariate analysis, were fasting plasma glucose level, duration of diabetes, plasma cholesterol, systolic blood pressure, and therapeutic regimen. A fasting plasma glucose level >11.1 mM (200 mg/dl) increased the risk of retinopathy to 3.6 times that for a level <7.8 mM (140 mg/dl); 74% of those who had background retinopathy and a baseline fasting glucose >11.1 mM (200 mg/dl) developed PDR. Over half of all participants with plasma cholesterol levels >7.8 mM (300 mg/dl) developed PDR in the follow-up interval. Elevated systolic blood pressure was a particularly significant risk factor for those with a long duration of diabetes. Proliferative retinopathy poses a serious health threat to Oklahoma Indians and represents a cause of visual impairment that may be preventable by early diagnosis of PDR and intervention with photocoagulation therapy. Determining whether glycemic and hypertensive control reduces the risk of PDR requires controlled clinical trials.