Background: Obesity may influence several physiologic processes involved in cataract formation such as oxidative stress, glycosylation and osmotic stress.
Objective: To examine the association between increased body mass index (BMI) and the incidence of cataract extraction.
Design and setting: The Nurses' Health Study and the Health Professionals Follow-up Study, both prospective cohort studies of US women and men.
Subjects: A total of 87 682 women and 45 549 men aged 45 y and older who did not have diagnosed cataract or cancer at baseline (1980 for women, 1986 for men).
Measurements: Cataract extractions occurring between baseline and 1996, confirmed by medical records.
Results: During 16 y of follow-up in the women, and 10 y in the men, (1 097 997 person-y), 4430 incident cases were documented. Compared to participants with BMI less than 23 kg/m(2), those with BMI greater than or equal to 30 kg/m(2) had 36% higher risk of any type of cataract (pooled multivariate relative risk (RR), 1.36; 95% CI, 1.23-1.49) after adjusting for smoking, age and lutein/zeaxanthin intake. The association was strongest for posterior subcapsular (PSC) cataract (pooled multivariate RR, 1.99; 95% CI, 1.55-2.55). With adjustment for diabetes, the RR of obesity associated with posterior subcapsular cataract was 1.68 (95% CI, 1.30-2.17). Obesity was not significantly associated with nuclear cataract.
Conclusion: Obesity increases the risk of developing cataract overall, and of PSC cataract in particular; the etiology of PSC cataract may be mediated at least in part by glucose intolerance and insulin resistance, even in the absence of clinical diabetes.