People who take aspirin more than once per week may be at increased risk for developing neovascular age-related macular degeneration (AMD), a prospective study has found.
The study was not randomized, however, and the findings await validation in future research, say Jie Jin Wang (University of Sydney, New South Wales, Australia) and fellow investigators.
Aspirin is one of the most widely used medications worldwide, but a recent study suggested a link between regular aspirin use and AMD, particularly the neovascular (wet) form of the disease.
To investigate, Wang et al analyzed information on 2389 adults who had participated in a prospective population-based cohort study. Participants enrolled in 1992-1994 were followed up for 15 years, during which time they had retinal photographs taken on four occasions.
At baseline 257 (10.8%) people were regular aspirin users, defined as taking the drug once or more per week in the past year, and 375 were occasional users, defined as taking the drug less than once per week in the past year. Aspirin use was validated against medication lists and bottles and the typical dose was 150 mg/day.
The incidence rate for neovascular AMD increased significantly with increasing aspirin use, from 2.2% in nonusers to 2.9% in occasional users and 5.8% in regular users. This trend was statistically significant.
Furthermore, the 15-year cumulative incidence of neovascular AMD was 9.3% in regular aspirin users and 3.7% in nonregular users, a highly significant difference. Interestingly, this difference became apparent only after 10-15 years, "suggesting that cumulative dosage is important in pathogenesis," say the authors.
After adjustment for age, gender, smoking, history of cardiovascular disease, and systolic blood pressure, regular aspirin use was associated with a 2.37-fold higher risk for AMD, Wang et al report in JAMA Internal Medicine.
The team notes that the result mirrors that of a European survey which found a 2.2-fold increased risk for neovascular AMD among regular aspirin users; other negative studies may be explained by the long "lead time" for development of aspirin-associated AMD, they suggest.
"We speculate that aspirin, which is known to increase complement activation in vitro and in vivo may also be associated with incident AMD via complement pathways," the researchers write.
Noting that clinical decisions regarding aspirin therapy are "complex and need to be individualized," they conclude: "Currently, there is insufficient evidence to recommend changing clinical practice, except perhaps in patients with strong risk factors for neovascular AMD (eg, existing late AMD in the fellow eye) in whom it may be appropriate to raise the potentially small risk of incident neovascular AMD with long-term aspirin therapy."
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