Aspirin Linked to Blinding Eye Disease
Aspirin and Macular Degeneration
For the new study, researchers in Australia followed more than 2,000 older adults. Doctors conducted detailed interviews at the start of the study, asking people about a variety of diet and lifestyle habits, including medication use. About 11% of people (257) were regular aspirin users, meaning they'd taken the drug at least once a week in the past year.
Study participants had regular eye exams to check for changes to their retinas.
Fifteen years later, 63 people in the study -- 15 regular aspirin users and 48 who rarely or never took it -- had developed “wet” macular degeneration.
Compared to people who never took aspirin, regular users were more than twice as likely to develop macular degeneration. That was true even after researchers accounted for other things known to influence a person’s risk for macular degeneration, including age, sex, smoking, heart disease, BMI, and high blood pressure.
The findings are published in the journal JAMA Internal Medicine.
Study Strengths and Limitations
The study doesn’t prove that aspirin causes macular degeneration. Different kinds of studies are needed to understand whether aspirin may directly harm the eye.
But one theory is that aspirin ramps up a part of the immune system called the complement system. Many people with macular degeneration carry a form of a gene that keeps them from being able to turn down the complement system when needed. Researchers say the result is that the immune system may be chronically overstimulated, causing damage to the back of the eye.
Indeed, when researchers looked just at people with the risk-conferring form of this gene, the association between macular degeneration and aspirin was even stronger. It was more than four times as high for regular vs. non-regular users, suggesting that there might be a biological basis for the association.
But other limitations make the findings less reliable. Researchers only asked about aspirin use once, for example, at the start of the study, so people who stopped taking aspirin might have been misclassified. And only half the people who started the study were followed for the full 15 years; so it's possible that people who were motivated to stick with the research may have been more concerned about their health and eyesight in general. It’s also possible that there were other differences between the groups that the study authors weren’t able to account for.