Link between Aspirin and Wet Age-Related Macular Degeneration
January 24, 2013 - Recently there have been stories in the news about a link between age-related macular degeneration (AMD) and the regular use of aspirin. This issue was first highlighted by a large European study, now the results of further studies have brought this issue to the fore again. These stories do not say that aspirin causes AMD. However, they do say that people who took aspirin regularly were more likely to have wet AMD.
The current news stories are based on two studies, both published in the Journal of the American Medical Association (JAMA) publications in the past month. The first was an ongoing study of nearly 5000 seniors in Beaver Dam, Wisconsin, which tracked their visual health and their history of aspirin use. The second was a study of over 2000 patients in Australia, which also looked for links between aspirin use and AMD. Regular aspirin use was defined as twice a week or more in the American study, and once a week or more in the Australian one.
None of these studies found any evidence that aspirin increased a person’s risk of developing dry AMD. However, both of the two new studies did suggest that people who took aspirin regularly for a long period of time (10-15 years) were more likely to develop wet AMD.
Many people take aspirin, but only a small percentage of people ever develop wet AMD. Although these studies showed that rates of wet AMD were doubled amongst those who took aspirin for a long time, the numbers of people affected are still quite small.
Interviewed in Medscape Medical News, Dr. Emily Chew, Deputy Director, at the U.S. National Eye Institute, advised heart patients not to discontinue aspirin use on the basis of these findings. "Doubling the risk sounds terrible," she said. "But the real risk for late-stage AMD in these people who took aspirin [in the Beaver Dam Study] is 1%, vs half a percent for those who didn't, which is not clinically meaningful."
“Patients need to keep in mind that these were retrospective, backward-in-time-looking studies that rely very heavily on patients’ recalling if they had used aspirin and how frequently,” says Dr. Kevin Gregory-Evans, Julia Levy BC Leadership Chair in Macular Research at UBC, and a member of the Foundation Fighting Blindness Board of Directors. “Because of this, retrospective studies are not the best way of proving something causes a disease. We all look forward to seeing the results of more powerful prospective studies.”
Other scientists concur that while these studies raise important questions, they do not provide enough evidence for doctors to advise their patients to make changes. An editorial in the medical journal that published the Australian research report states that the results are not strong enough evidence to provide clinical direction.
"These results of large studies that link aspirin and wet AMD do raise concerns," says Dr. Bill Stell, Foundation Fighting Blindness Expert Scientific Advisor, "but they do not show that taking aspirin causes wet AMD. These findings will prompt more study of whether aspirin could have this effect, and if so, how. For now, we should remind ourselves that all of these studies show only a tendency for aspirin use and wet AMD to occur together. It would be just as logical to conclude that an underlying disease process, which predisposes people to develop wet AMD, makes them more likely to take aspirin regularly."
If you have AMD or are at risk of AMD because of a history of it in your family, and you are concerned about your own aspirin use, talk to your family doctor. If your doctor or specialist has recommended that you take aspirin, you shouldn’t stop taking it on your own. It would be better to ask your doctor to suggest an acceptable alternative.
“If a link is established there are many alternatives to aspirin that physicians can prescribe, both for its pain-killing effects and its cardiovascular protective effects,” says Dr. Gregory-Evans.
Dr. Gregory-Evans also notes that there are many other factors that influence AMD. “Other risk factors, especially smoking, cause wet AMD much more convincingly than the evidence published here for aspirin. Stopping smoking should be seen as the most important priority in wet AMD.”
Learn more about reducing the risk of AMD.