Aspirin (ASA) had no protective effect on myocardial infarction (MI) in patients with rheumatoid arthritis (RA) when used as primary prophylaxis, a recent study found. Subjects with RA were aged ≥60 years in a population-based health database. Researchers excluded patients with history of MI, angina, stroke, peripheral vascular disease, or coronary artery procedures. They performed a case-crossover study with each subject contributing a hazard period and a control period 90 days prior to the MI. In addition, to minimize confounding by indication, a propensity score (PS)-matched cohort study was performed, considering all patients with RA with an incident prescription of low-dose ASA as the exposed group. They found:

• There was no protective effect in the case-crossover study, with 55 subjects exposed in the hazard period and 44 in the control period.
• Similarly, among 1,836 subjects included in the PS-matched cohort study (918 ASA users and 918 ASA non-users), there was no protective effect of low ASA on MI.