A team of Australian scientists has found that regular aspirin consumption is associated with an increased risk of a disease called age-related macular degeneration, a leading cause of blindness in older people.

The research, published in the journal JAMA Internal Medicine, shows that the risk appears to be independent of a history of smoking, which is also a known preventable risk factor for neovascular age-related macular degeneration (AMD).

Aspirin, also known as acetylsalicylic acid, is commonly used in the prevention of cardiovascular disease, such as myocardial infarction and ischemic stroke.

While a five-year European study published last year suggested that regular aspirin use – defined as once or more per week in the past year – was associated with AMD, other studies had reported inconsistent findings. The new study was conducted over a much longer period and found clear evidence of the risk.

The team conducted an analysis of data from an Australian study – the Blue Mountains Eye Study – that included four examinations during a 15-year period. Of 2,389 participants, 257 individuals (10.8 percent) were regular aspirin users. After the 15-year follow-up, 63 individuals from the 2,389 participants developed incident neovascular AMD.

“The cumulative incidence of neovascular AMD among nonregular aspirin users was 0.8 percent at five years, 1.6 percent at 10 years, and 3.7 percent at 15 years,” said study co-author Prof Paul Mitchell of the Westmead Millennium Institute for Medical Research’s Centre for Vision Research.

“Among regular aspirin users, the cumulative incidence was 1.9 percent at five years, 7 percent at 10 years and 9.3 percent at 15 years, respectively, indicating that regular aspirin use is significantly associated with an increased incidence of neovascular AMD. This increase was around 2.5-fold, after accounting for potentially confounding variables.”

The scientists noted that any decision concerning whether to stop aspirin therapy is “complex and needs to be individualized.”

“Currently, there is insufficient evidence to recommend changing clinical practice, except perhaps in patients with strong risk factors for neovascular AMD in whom it may be appropriate to raise the potentially small risk of incident neovascular AMD with long-term aspirin therapy,” they concluded.

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Bibliographic information: Gerald Liew et al. 2013. The Association of Aspirin Use With Age-Related Macular Degeneration. JAMA Intern Med., published online before print; doi: 10.1001/jamainternmed.2013.1583