People who take aspirin regularly are more likely to develop the 'wet' form of age-related macular degeneration compared to people who rarely or never take the drug, research has suggested.
Aspirin is widely used as a painkiller and to help prevent heart problems and stroke. University of Oxford studies in 2012 also suggested that taking an aspirin a day may help prevent and slow cancer growth.
All medicines carry some risks as well as benefits. Occasional aspirin use does not appear to be a reason for concern. The risk of eye problems found by researchers was among people who took aspirin every day for up to 15 years.
Macular degeneration is a leading cause of blindness in older adults. The 'wet' form is less common but progresses more rapidly and is more likely to lead to vision loss than the 'dry' form.
In wet macular degeneration, tiny new blood vessels grow under the retina, the light-sensing part of the eye. It’s not clear why this happens. These blood vessels break open and leak, causing scar tissue to form. Over time, the scar tissue clouds central vision.
Both kinds of macular degeneration become more common as people age. Beyond age, the only risk factor that’s consistently been linked to the condition is smoking.
Eyes and aspirin
News that aspirin may be linked to macular degeneration surfaced in 2012 when a large European study found that regular aspirin users were more likely to develop AMD.
Before that, two large studies found no association between aspirin and macular degeneration. Another study had even suggested that aspirin might protect against the dry form of the disease.
An Australian study published in JAMA Internal Medicine in 2013 followed more than 2,000 older adults. About 11% of the people taking part had taken aspirin at least once a week in the previous year.
15 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 wet 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 research doesn’t prove that aspirin causes wet macular degeneration. Different kinds of studies are needed to understand whether aspirin may directly harm the eye.
How might aspirin damage eyesight?
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.
JAMA Internal Medicine. Liew G, Mitchell P, Wong TY, et al. The association of aspirin use with age-related macular degeneration.
Klein, B. Journal of the American Medical Association, Dec. 19, 2012.
Prevent Blindness America: Vision Problems in the US.
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