Using aspirin on a regular basis for 10 years or more during middle-to-old age could increase the risk for the developing incident age-related macular degeneration (AMD), indicate study results.
While the number of incident cases of the condition was small overall, the finding indicates a significant association between use of the drug and the eye condition, write the researchers in JAMA.
By contrast, the findings showed that aspirin use in the 5 years prior to observed incidence had no significant association with AMD.
"If confirmed, defining the causal mechanisms may be important in developing methods to block this effect to prevent or retard the development of neovascular AMD in persons who use aspirin, especially to prevent CVD [cardiovascular disease]," say Barbara Klein (University of Wisconsin School of Medicine and Public Health, Madison, USA) and colleagues.
The team explains that regular aspirin use is common and becoming more widespread in the USA among those in the age-range most at risk for AMD.
Using data from the Beaver Dam Study spanning 20 years of follow up, the researchers examined aspirin use and AMD incidence among 4926 individuals aged 43-86 years who underwent a baseline examination between 1988 and 1990, then 5-yearly follow ups thereafter. Regular aspirin use was defined as twice weekly or more for more than 3 months.
After a mean follow up of 14.8 years, 512 participants developed incident early AMD, and 117 developed incident late AMD, giving an incidence rate of 0.164 and 0.027 per 10 person-years, respectively.
The authors report no significant association between self-reported aspirin use 5 years prior to incidence of early AMD, and while late AMD incidence was greater among those who had been using aspirin for this length of time, at 1.4% versus 1.0%, it was a nonsignificant association.
In analysis of 10-year aspirin use, the risk for incidence of late AMD was significantly higher for those who used the drug regularly, with a hazard ratio (HR) of 1.63, compared with individuals who did not. This significant association remained for neovascular subtype AMD (HR=2.20), but was lost for pure geographic atrophy (HR=0.66), note Klein et al.
The team observed no significant association between 10-year aspirin use and early AMD.
"If our finding is borne out in other studies, it suggests that the effect of aspirin on mechanisms leading to AMD may be different, at least partially, from aspirin's immediate effects on clotting, which seem to be responsible for cardioprotection," conclude the authors.
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