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Smoking Associated With Cataract Risk
Smoking cessation has been associated with a steady decrease in risk for cataracts, but even 2 decades after quitting, that risk is still higher than in those who have never smoked, according to a new study. This new analysis supports a growing body of literature that shows a relationship between smoking and the risk for cataracts.
In an analysis of Swedish men, lead author Birgitta Ejdervik Lindblad, MD, PhD, from the Department of Ophthalmology, Örebro University Hospital; the School of Health and Medical Sciences, Örebro University; and the Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, and colleagues found a significant dose–response relationship between smoking and the need for cataract extraction. Conversely, smoking cessation was associated with a decrease in risk that accumulated over time.
These findings “add to numerous previous epidemiologic studies on the association between smoking and cataract,” the authors write. “Although the relative risk estimates vary, most studies have reported a positive association between smoking and cataract.” The study was published online January 2, 2014, in JAMA Ophthalmology.
The data come from the Cohort of Swedish Men, a large, prospective cohort study begun in 1997 to examine the association between lifestyle and chronic diseases such as cataracts. Questionnaires were sent to all Swedish men between the ages of 45 and 79 years living in 2 counties in central Sweden; responses were received from 48,645 (48.5%) of them. Dr. Lindblad and coauthors followed-up the men until the date of cataract extraction, death, or the end of follow-up on December 31, 2009.
The study included a total of 44,371 men, of whom 24.9% were current smokers, 38.8% were past smokers, and 36.3% were never smokers when follow-up began in 1998. The mean number of cigarettes smoked daily was 13.9 (standard deviation [SD], 6.3) among current smokers and 13.6 (SD, 6.6) among past smokers.
During 12 years of follow-up, 5713 cases of age-related cataract extraction occurred. On age-adjusted analysis, past or current smoking was associated with a relative risk for cataract extraction of 1.21 (95% confidence interval [CI], 1.15 – 1.28), or a 21% increase in the risk for cataract extraction compared with never smoking. In a multivariate analysis adjusted for diabetes mellitus, hypertension, corticosteroid medication, alcohol consumption, use of vitamin supplements, body mass index, and educational level, ever smoking was associated with a relative risk of 1.18 (95% CI, 1.12 – 1.25) for cataract extraction compared with never smoking.
The authors also observed a relationship between smoking intensity and cataract risk compared with never smoking, ranging on age-adjusted analysis from 1.11 (95% CI, 0.99 – 1.23) with 1 to 5 cigarettes per day to 1.40 (95% CI, 1.30 – 1.51) with more than 15 cigarettes per day (P < .001 for trend) for ever smokers. On multivariate analysis, the relative risk was 1.11 (95% CI, 1.00 – 1.24) with 1 to 5 cigarettes per day and 1.35 (95% CI, 1.25 – 1.46) with more than 15 cigarettes per day (P < .001 for trend). Men who currently smoked more than 15 cigarettes per day had the highest relative risk, at 1.42 (95% CI, 1.28 – 1.58), compared with never smokers.
Smoking cessation was associated with a steadily decreasing risk for cataract extraction. Smokers who had quit less than 10 years before had a relative risk of 1.32 (95% CI, 1.19 – 1.46) on the age-adjusted analysis and 1.27 (95% CI, 1.15 – 1.41) on the multivariate analysis. At 10 to 20 years after quitting, the relative risks were 1.25 (95% CI, 1.16 – 1.36) and 1.22 (95% CI, 1.12 – 1.32), respectively, and at more than 20 years, the relative risks were 1.14 (95% CI, 1.06 – 1.23) and 1.13 (95% CI, 1.04 – 1.22), respectively (P < .001 for trend).
Study limitations include lack of information on cataract type, reliance on retrospective recall to estimate lifetime cigarette smoking, and no data on sunlight exposure, which also can influence cataract risk, the authors write. , “Since smoking is also related to other ocular diseases, strategies to prevent smoking and promote smoking cessation are important, and eye care professionals should encourage people to stop smoking,” the authors conclude.
These findings confirm what researchers have known for more than a decade: Smoking contributes to cataract development, said Kevin Miller, MD, professor of clinical ophthalmology at the Jules Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles. He cited research dating back to 2000 showing an association between smoking and cataracts, saying, “if you stop smoking you don’t lower your risk, but you stop accumulating risk.”
Dr. Miller told Medscape Medical News, “I don’t think this information is going to change any smoker into a nonsmoker. If the thought of getting lung cancer, bladder cancer, esophageal cancer, chronic obstructive pulmonary disease, strokes, or heart attacks doesn’t throw you off smoking, the idea of getting cataracts probably won’t do it either.”
The best answer, as always, is keeping people off cigarettes.
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