Determines whether age influences the effects of smoking on age-related macular degeneration (AMD) risk.
The American Journal of Ophthalmology publishes the findings in its January edition.
"The take-home message is that it's never too late to quit smoking," said lead author Dr. Anne Coleman, professor of ophthalmology at the Jules Stein Eye Institute at UCLA. "We found that even older people's eyes will benefit from kicking the habit."
Age-related macular degeneration causes progressive damage to the macula, the center of the retina that allows us to see fine details. When the macula degenerates, people experience darkness or blurring in their central vision, preventing them from being able to read, drive and recognize faces.
After age, smoking is the second most common risk factor for AMD. This study sought to determine whether age influences the effects of smoking on AMD risk.
Coleman and her colleagues followed a group of 1,958 women who underwent retinal photographs at five-year intervals, starting with a baseline exam at age 78. Four percent, or 75 of the women, smoked.
The researchers compared the retinal images at ages 78 and 83 to check for the appearance of AMD, and evaluate whether smoking affected the women's likelihood of developing the disease.
"Age is the strongest predictor for AMD, yet most of the research in this field has been conducted in people younger than 75," explained Coleman. "Our population was considerably older than those previously studied. This research provides the first accurate snapshot of how smoking affects AMD risk later in life."
Overall, women who smoked had 11 percent higher rates of AMD than other women their same age. In women over 80, however, those who smoked were 5.5 times more likely to develop AMD than women their age who did not smoke.
"We saw a slightly higher rate of AMD in women after age 80, but the rate was dramatically higher in older women who smoked," said Coleman. "The bottom line is that AMD risk increases with age. And if you smoke, your risk of developing the disease rises even more."
Cigarette smoking has been hypothesized to increase AMD risk by reducing serum antioxidant levels, altering blood flow to the eyes and decreasing retinal pigments.
"This study provides yet another compelling reason to stop smoking and suggests that it is never too late to quit," said Dr. Paul Sieving, director of the National Eye Institute.
The National Eye Institute and National Institute on Aging funded the research. About 1.75 million U.S. residents suffer from advanced AMD with vision loss; the number is expected to grow to almost 3 million by 2020.
Coleman's coauthors included Carol Mangione, Robin Seitzman and Fei Yu of UCLA; Steven Cummings and Katie Stone of the California Pacific Medical Center Research Institute; Jane Cauley from the University of Pittsburgh; Kristine Ensrud from the University of Minnesota; Marc Hochberg from the University of Maryland; Kathryn Pedula from the Kaiser Permanente Center for Health Research; and Edgar Thomas from the Retina Vitreous Associates Medical Group.