People who regularly took aspirin 10 years prior to examination had a small but statistically significant increase in the risk of a subtype of age-related macular degeneration (AMD), according to a study by University of Wisconsin-Madison researchers.
Dr. Barbara Klein and her collaborators studied nearly 5,000 people who took part in the UW School of Medicine and Public Health's Beaver Dam Eye Study. Results are being published in the Dec. 19 Journal of the American Medical Association.
"Aspirin use in the United States is widespread, with an estimated 19.3 percent of adults reporting regular consumption, and reported use increases with age," according to background information in the study.
Prevalence of AMD, a potentially blinding condition, also increases with age. The National Eye Institute, which funds the Beaver Dam Eye Study, estimates that 1.75 million Americans have AMD, including more than 15 percent of white women older than 80. But until now, studies failed to show a consistent relationship between aspirin use and AMD.
Klein, a professor of ophthalmology and visual sciences, looked at data from eye exams performed on Beaver Dam participants every five years over a 20-year period (1988-1990 through 2008-2010). Participants were asked if they had regularly used aspirin at least twice a week for more than three months at each eye examination.
For the study, the researchers measured the incidence of different types of AMD (early, late, and two subtypes of late AMD -- neovascular AMD and pure geographic atrophy).
There were 512 cases of early AMD and 117 cases of late AMD over the course of the study. The researchers found that regular aspirin use 10 years before the retinal exam was associated with late AMD (age- and sex-adjusted incidence, 1.8 percent for users vs. 1.0 percent for nonusers). They found a significant association with one subtype of late AMD, neovascular AMD (age-and sex-adjusted incidence, 1.4 percent for users compared with 0.6 percent for nonusers). There was no significant association for the other subtype or for early AMD.
"Our findings are consistent with a small but statistically significant association between regular aspirin use and incidence of neovascular AMD," the authors wrote. They said that if further studies confirm the link, it will be important to develop ways to block or slow the effect, especially for people who use aspirin to prevent cardiovascular disease.
Journal of the American Medical Association