Can aspirin cause blindness?
Australian researchers suggest an association between daily aspirin and the development of macular degeneration. The study, published recently (January 22, 2013, JAMA Internal Medicine), describes the results of a 15 year prospective review of about 2400 participants and their use of aspirin, heart disease and AMD risk factors.
About 10% of the participants reported regular aspirin use. Aspirin is often used by people who are at high risk for developing a heart attack.
Aspirin Increases Risk of AMD
In summary, there was an increase in wet ARMD with regular aspirin use compared to those who do not take the drug regularly. Over the 15 year study, the prevalence of wet ARMD increased as well.
Risk of wet ARMD increased to 1.9% (0.8%) at 5 years, 7% (1.6%) and 9.3% (3.7 %) at 15 years (Value within parentheses = no aspirin).
Randomized Clinical Trials Are Best
The FDA ensures we practice evidenced based medicine by not approving anything without conclusive evidence.
Evidenced based medicine means that the drugs and procedures we prescribe have been scientifically and statistically proven to work. Clinical studies (testing the drug on patients) are designed to remove any effect of “chance” on the results.
The best clinical trials to provide these meaningful statistics are called Randomized Clinical Trials. The best way to remove “chance” is to randomize patient selection and “mask” many of the tested variables.
For instance, patients should be randomly selected. They are given either a drug or a placebo. No one knows until the study is complete. Independent doctors will evaluate the patients after receiving the test drug or placebo.
What Does This Mean?
We don’t really know for sure if aspirin causes macular degeneration.
While the study does suggest a causal relationship between aspirin use and the development of wet ARMD, there are several limitations to the study.
There is heavy study bias. In other words, the study is not objective. The results may have occurred due to chance.
The researches included 2400 individuals from a region in Australia who volunteered to participate. A better study would have randomly selected participants instead of choosing members of the same group. Attendees of the Super Bowl, for instance, are a group. They share many commonalities.
The participants were questioned about their aspirin use. In a prospective trial, candidates would have been given the drug (or not) and then examined for effects.
On the other hand, “studies” such as this are beneficial by raising questions and more economical than a randomized trial.
If other studies have similar findings, a randomized clinical trial will be designed to answer this definitively This is the same situation with the effects of Omega-3. For now, we just don’t know.
Lastly, my recommendation for those on aspirin. Get regular dilated eye exams and consult your doctor regarding your need for aspirin.
Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist
2 replies on “Does Aspirin Cause Macular Degeneration?”
Great article, Randy – not only about aspirin but also the structure of valid clinical tests!
Thanks for the support and kudos. I really appreciate the comments and participation.