NEW YORK (Reuters Health) Jan 15 – The risk of cataract extraction decreases over time following smoking cessation, but after more than two decades still does not reach the risk level of those who have never smoked, according to a report in the January 1st issue of the American Journal of Epidemiology.
Dr. June M. Weintraub and colleagues from Harvard Medical School, in Boston, Massachusetts, prospectively examined the association between time since quitting smoking and incidence of cataract extraction in patients enrolled in the Nurses' Health Study and the Health Professionals Follow-up Study. "There were 4281 incident physician-confirmed cases of cataract and 1,038,493 accumulated person-years of follow-up," they note.
After adjustment for age, average number of cigarettes smoked per day, and other risk factors, former smokers who had quit at least 25 years ago had a 20% lower risk of cataract extraction than current smokers. "However, risk among past smokers did not decrease to the level seen among never smokers" (RR = 0.64), the team notes.
They observed a similar relationship when they examined the data by cataract subtype. For primary nuclear cataract and primary posterior subcapsular cataract, former smokers who had quit at least 25 years ago had a decreased risk of cataract extraction compared with current smokers (RR = 0. 82 and 0.90, respectively).
"Our finding that the excess risk of cataract extraction persists after quitting smoking and only moderately decreases with years since quitting provides further support for the hypothesis that smoking causes irreversible damage to the lens," Dr. Weintraub and colleagues conclude.
"The mechanism by which smoking confers increased risk of cataract is hypothesized to be due to the oxidative action of inhaled toxins in cigarette smoke," Dr. Weintraub told Reuters Health.
"The gas phase of cigarette smoke contains many toxins, including free radicals that can initiate oxidation of biological target molecules; smoking also increases the rate of lipid peroxidation," she continued. "The damage to the lens by these mechanisms may be responsible for the accumulation of proteins leading to cataract."
Am J Epidemiol 2002;155:72-79.