Proliferative Retinopathy in NIDDM Incidence and Risk Factors in Pirna Indians ROBERT G. NELSON, JOHN A. WOLFE, MARK B. HORTON, DAVID J. PETTITT, PETER H. BENNETT, AND WILLIAM C. KNOWLER The incidence of proliferative diabetic retinopathy was determined in the Pima Indians of the Gila River Indian Community in Arizona. Over 4 yr, this complication developed in 25 of 953 subjects >9 yr of age with non- insulin-dependent diabetes. No cases were diagnosed in <35-yr-old subjects, and the incidence was strongly related to the duration of diabetes. The cumulative incidence of proliferative retinopathy after 20 yr duration was 14%. All cases of proliferative retinopathy occurred in subjects with background retinopathy. Younger age at diagnosis of diabetes was associated with a higher incidence of proliferation when subjects with diabetes of similar duration were compared. A higher incidence of proliferative retinopathy, after controlling for age, sex, and diabetes duration, was associated with hypertension, proteinuria, renal insufficiency, absence of Achilles tendon reflex, elevated total serum cholesterol concentration, and insulin therapy. Diabetes 38:435-40,1989 P roliferative retinopathy is a vision-threatening mi- crovascular complication of diabetes in which new vessels grow on the surface of the retina and into the vitreous body. Subsequent hemorrhages and fibrous tissue proliferation, often associated with retinal de- tachment, cause severe impairment of vision. A previous study found that the incidence of proliferative retinopathy is greater in insulin-dependent (IDDM) than non-insulin-de- pendent (NIDDM) diabetes mellitus when people with similar Glucose 1 mM = 18mg/dl From the Diabetes and Arthritis Epidemiology Section, National Institute of Diabetes and Digestive and Kidney Diseases; and the Department of Oph- thalmology, Phoenix Indian Medical Center, Indian Health Service, Phoenix, Arizona. Address correspondence to Dr. Robert G. Nelson, National Institute of Di- abetes and Digestive and Kidney Diseases, 1550 East Indian School Road, Phoenix, AZ 85014. Received for publication'5 July 1988 and accepted in revised form 27 October 1988. duration of diabetes are compared (1). This suggests that different factors may be related to the development of pro- liferative retinopathy in each type of diabetes. Although pro- liferative retinopathy has been the focus of intensive clinical investigation, much remains unknown regarding the risk fac- tors for this diabetic complication. In this study, the incidence of proliferative retinopathy among people with diabetes was determined in the Pima Indians of the Gila River Indian Community in Arizona, a population in whom IDDM is unknown (2,3) but who have the world's highest reported incidence and prevalence of NIDDM (4). Predictors of proliferative retinopathy were iden- tified, and the incidence of this complication in diabetic Pima Indians was compared with reports from other populations. Retinal lesions are very rare in nondiabetic Pimas, but typical diabetic retinopathy occurs in the diabetic subjects (5). MATERIALS AND METHODS The National Institutes of Health has conducted a longitu- dinal study of diabetes and its complications in the Gila River Indian Community of Arizona since 1965 (6). This community is inhabited primarily by Pima and Papago Indians. Approx- imately every 2 yr, each resident of the community who is at least 5 yr of age is asked, regardless of health, to participate in a standardized medical examination. These biennial examinations include direct ophthalmos- copy performed by a physician (after pupillary dilation in subjects at least 15 yr of age). Background retinopathy was considered present if the subject had one or more micro- aneurysms, exudates, or hemorrhages. Proliferative retinop- athy was considered present if the subject had neovascu- larization or vitreous hemorrhage, rubeosis iridis, or retinal detachment believed to be due to neovascularization of di- abetic origin. Blood pressure was measured in the right arm with the subject at rest in the supine position. Systolic and diastolic blood pressures were measured at the first and fourth Korotkoff sounds, respectively. Laboratory tests performed at each biennial examination included measurement of serum cholesterol and creatinine DIABETES, VOL. 38, APRIL 1989 435 Downloaded from http://diabetesjournals.org/diabetes/article-pdf/38/4/435/357028/38-4-435.pdf by guest on 04 November 2022