The increased risk only occurred with people who had taken aspirin regularly 10 years before they were diagnosed with the potentially blinding eye disease. They had taken aspirin at least twice a week for more than three months, says researcher Barbara E.K. Klein, MD, MPH.
The risk was for the type of macular degeneration known as wet or neovascular AMD, says Klein, professor of ophthalmology and visual sciences at the University of Wisconsin School of Medicine, Madison.
Wet macular degeneration is generally more severe than another version, known as dry macular degeneration.
Although people taking aspirin regularly were two times more likely to get the condition, Klein says the absolute risk is still low because the condition is not common. About 1% of people aged mid-40s and older get wet macular degeneration, she says.
Klein studied nearly 5,000 men and women, ages 43 and older. She followed them for 20 years, although not all of them stayed in the study that long.
The research is published in the Journal of the American Medical Association.
Aspirin & Eye Problems: Study Details
Previous research findings about aspirin use and macular degeneration risk have been mixed.
As aspirin use and macular degeneration are increasing, Klein decided to follow men and women over many years to see if she could find a link.
The macula is a small area of the retina, the tissue lining the back of the eye, that is responsible for central vision.
Klein looked at wet (late) and dry (early) macular degeneration for the study. Both are potentially blinding conditions.
Over the course of the study, 512 people were diagnosed with early AMD and 117 with late AMD.
Although regular use of aspirin 10 years before the diagnosis was linked with late macular degeneration, aspirin use five years before the diagnosis was not linked with an increased risk of either form of AMD.
Klein can't explain the link and says it requires more study. "The absolute risk of this is small," she says. "There are so many folks who have been put on aspirin for [heart disease] prevention. ... The [heart] protective effect is still primo."
One co-author, Ronald Klein, MD, MPH, has served as a consultant for Pfizer, which makes AMD medicine. The study was funded by the National Institutes of Health and support from Research to Prevent Blindness.
Aspirin & Eye Problems: Perspective
"This study is suggestive that there may be a relationship but it is by no means definitive," says George Williams, MD, professor and chair of the department of ophthalmology at Oakland University's William Beaumont School of Medicine in Rochester, Mich.
Williams says a weakness in the study is that the men and women self-reported the aspirin use, so it may not have been totally accurate.
If a cardiologist has recommended aspirin for heart disease protection, Williams says, "I would not take anyone off it."
People who take aspirin regularly should consider their risk of macular degeneration and the benefits of taking aspirin, says Michael Tolentino, MD, medical director of the Macular Degeneration Association and an ophthalmologist in Lakeland, Fla.
People at higher risk for the disease include those with a family history, those with light eyes, and smokers.
"Everything is a risk-benefit ratio," he says.
He reports serving as consultant for Novartis, Genentech, Alarcon, and other companies involved in eye drugs.