BODY-MASS INDEX - AN INDEPENDENT PREDICTOR OF CATARACT

Objective: To examine whether body mass index is an independent predic tor of cataract. (Body mass index is a standardized measure defined as weight in kilograms divided by the square of the height in meters.) D esign: Prospective cohort study, with 5 years of follow-up. Participan ts: A total of 17 764 US male physicians participating in the Physicia ns' Health Study, aged 40 to 84 years, who were free of cataract, myoc ardial infarction, stroke, and cancer at baseline and reported complet e information about body mass index and other cataract risk factors. M ain Outcome Measure: Incident cataract, defined as a self-report, conf irmed by medical record review, first diagnosed after randomization, a ge-related in origin, and responsible for a decrease in best corrected visual acuity to 20/30 or worse. Results: Incident cataract occurred during follow-up in 370 participants. In proportional hazards models t hat adjusted for potential confounding variables, body mass index had a strong, graded relationship with risk of cataract. Relative to those with body mass index less than 22, relative risks (95% confidence int ervals) associated with body mass index of 22 to less than 25, 25 to l ess than 27.8, and 27.8 or more were 1.54 (1.04 to 2.27), 1.46 (0.98 t o 2.20), and 2.10 (1.35 to 3.25),respectively. Relative to any given l evel of body mass index, a 2-unit higher level predicted a 12% increas e in risk of cataract (95% confidence interval, 5% to 19%). Higher bod y mass index was especially strongly related to risk of posterior subc apsular and nuclear sclerotic cataracts and was also significantly rel ated to risk of cataract extraction. Conclusions: In a prospective coh ort study of apparently healthy men, higher body mass index, a potenti ally modifiable risk factor, was a determinant of cataract. The leanes t men had the lowest rates, consistent with experimental evidence that restriction of energy intake slows development of cataract. Although precise mechanisms are unclear, the effect of body mass index on catar actogenesis is apparently independent of other risk factors, including age, smoking, and diagnosed diabetes.