Intensity of smoking and smoking cessation in relation to risk of cataract extraction: a prospective study of women.

The authors investigated the association of smoking and smoking cessation with the incidence of cataract extraction in a population-based prospective cohort study. A total of 34,595 women aged 49-83 years in the Swedish Mammography Cohort were followed from September 1997 through June 2002. Information on smoking, diet, and other lifestyle factors was collected through a self-administered questionnaire. A total of 2,128 cases of age-related cataract extraction were identified. Relative risks were estimated as rate ratios using Cox proportional hazards models. The authors observed a significant dose-response association between intensity of smoking and risk of cataract extraction (among current smokers, p for trend = 0.02; among past smokers, p for trend = 0.0002). After cessation of smoking, the risk decreased with time. Among women with a moderate lifetime smoking intensity (6-10 cigarettes/day), the relative risk was not significantly different from the risk among never smokers 10 years after smoking cessation. Among women who had smoked more intensively (>10 cigarettes/day), after 20 years of nonsmoking the increased risk became small and no longer statistically significant in comparison with never smokers (for trend over time, p < 0.0001). This prospective study confirmed smoking as a risk factor for cataract, with a dose response for smoking intensity. Smoking cessation predicts reduced risk over time, but a longer period of time is needed with a higher smoking intensity.