Cumulative Lead Exposure and Incidence of Age-related Cataract in Older Men

Abstract

Purpose: Cumulative lead exposure has been suggested as a risk factor for age-related cataract (ARC) A previous study in a cohort of elderly men reported a significant association between cumulative lead exposure and risk of ARC. Here, we extended this analysis and examined new incident cases of ARC in relation to lead exposure. We also evaluated potential effect modification by dietary intake of antioxidant vitamins, calcium and iron. Methods: This study includes ARC-free 632 males (mean age=66.2±6.4 years) from the Normative Aging Study who had tibia and patella lead levels measured by K X-ray fluorescence (KXRF) from 1991 to 1999. Cataract status was graded through Slit Lamp Exam and ARC cases were defined as those who had cataract surgery or were diagnosed as any subtype of cataract grade 3 or higher. Cox proportional hazards model was used to estimate hazard ratio (HR) and 95% confidence interval (CI) of incident ARC. Calorie-adjusted daily intake of iron, calcium, vitamin D, vitamin C, vitamin E and carotenoids were computed and dichotomized at the median (low vs. high) for testing effect modification. Results: Of 632 participants, we identified 208 incident ARC at the end of follow-up (316 cases/10,000 person years). After adjusting for important confounders, tibia lead was significantly associated with incident ARC (HR per interquartile range increase (IQR:15 μg/g) =1.21, 95% CI: 1.05, 1.40, p=0.03). We found a weaker and non-significant association with patella lead (HR per IQR increase (20 μg/g) =1.05, 95% CI: 0.52, 2.11, p=0.11). The association between tibia lead and ARC was stronger in people with lower carotene intake and higher intake of vitamins C, D and E and iron and calcium but the interaction terms were not statistically significant . Conclusions: Our findings reinforce that cumulative lead exposure is an important risk factor for ARC. We found no consistent patterns in effect modification by nutrients.