Does Aspirin Use Increase the Risk of Age-Related Macular Degeneration: A Population-Based Comparative Cohort Study

Background: Aspirin is important and a valuable antiplatelet agent in clinical practice. Evaluating the risk of age-related macular degeneration (AMD) among long-term aspirin users compared with non-users is not fair due to confounding by indication. This study is aimed to estimate the risk of AMD among aspirin users compared with clopidogrel. Method: We conducted a population-based retrospective comparative cohort study using Taiwan's Longitudinal Health Insurance Database (LHID), which was randomly selected from the National Health Insurance Research Database (NHIRD). We included patients more than 45 years-old who initiated aspirin during 2001-2010 and they all tracked to 2013. The comparison groups are patients who were prescribed clopidogrel. The outcome of interest was AMD defined by ICD-9-CM code of 362·50-52 or 362·57. We used multivariate Cox regression modeling and propensity score matching to balance the characteristics of patients between groups to estimate the hazard ratio. Findings: After applying the methods, we had 109,534 aspirin users and 3,619 clopidogrel users. Male gender (51·12%) was predominate over females (48·88%) in the aspirin-user group. Our results showed no significant different risk of AMD between aspirin and clopidogrel users, while the multivariate Cox model showed HR was 1·13 (95% CI, 0·97 - 1·32) and the PS model showed HR was 1·09 (95% CI, 0·54-2·17). The incidence of aspirin users developing AMD was 8·18 per person-year, while the incidence of clopidogrel users was 10·07 per person-year. Interpretation: Patients with long-term use of aspirin did not have a higher risk of developing AMD compared to clopidogrel users. Funding: None. Declaration of Interest: All authors declare no conflict of interest. Ethical Approval: The study protocol was approved by the National Cheng Kung University Hospital Institutional Review Board (IRB) (NCKUH-IRB-A-EX-105-009).