1. Current smokers of more than 15 cigarettes per day had a 42% increased risk of cataract extraction compared to never smokers.
2. After quitting for more than 20 years, men who previously smoked 15 cigarettes or more a day had a 21% increased risk of cataract compared to never smokers.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Smoking has been clearly linked to many ophthalmologic conditions, including cataract development. However, the impact of smoking cessation on cataracts is not as clear. This study showed that smoking cessation was associated with a decline in the rate of cataract development. Strengths of the study include its prospective nature, as well as the large cohort size. The study is limited in that detection of incidences of cataract was done by reviewing a registry for cataract extractions, rather than diagnosis of cataract. Moreover, the study only included male patients aged 45 to 79 years, and thus is not generalizable. Finally, the 95% confidence interval of relative risk of cataract extraction for current smokers of more than 15 cigarettes per day overlaps with the that of past smokers more than 20 years after cessation, suggesting little difference between the two groups.
Relevant Reading: Effects of smoking on ocular health
In-Depth [prospective cohort study]: This study examined patients derived from the Cohort of Swedish Men, which included all men in central Sweden aged 45-79 years that completed a self-administered questionnaire about diet and lifestyle factors. Men who returned blank questionnaires, had a diagnosis of cancer, were missing data about smoking status, died before baseline, or had cataract extraction before baseline, were excluded. Cataract incidence was determined by matching patient identification numbers to a Swedish surgery register to find cases of cataract extraction surgery.
A total of 44,371 men were included in the study, of which 24.9% were current smokers, 38.8% were past smokers, and 36.3% were never smokers. Adjusted for age, ever smokers had a 21% increased risk of having a cataract extraction. Current smokers who smoked 15 or more cigarettes per day had a relative risk of 1.42 (95% CI, 1.28-1.58). After smoking cessation, risk of cataract extraction decreased with time (P<0.001). More than 20 years after smoking cessation, the adjusted relative risk for past smokers was 1.21 (95% CI, 1.06-1.39).
By James Jiang
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