Influence of Acetylsalicylic Acid Use on Risk and Outcome of Community-Acquired Staphylococcus aureus Bacteremia: A Population-Based Study

OBJECTIVE: To investigate the influence of acetylsalicylic acid (ASA) use on risk and outcome of community-acquired Staphylococcus aureus bacteremia (CA-SAB). METHOD: We used population-based medical databases to identify all patients diagnosed in northern Denmark with first-time CA-SAB and matched population controls from 2000–2011. Categories for ASA users included current users (new or long-term users), former users, and nonusers. The analyses were adjusted for comorbidities, comedication use, and socioeconomic indicators. RESULTS: We identified 2638 patients with first-time CA-SAB and 26 379 matched population controls. Compared with nonusers, the adjusted odds ratio (aOR) for CA-SAB was 1.00 (95% confidence interval [CI], 0.88–1.13) for current users, 1.00 (95% CI, 0.86–1.16) for former users, 2.04 (95% CI, 1.42–2.94) for new users, and 0.95 (95% CI, 0.84–1.09) for long-term users. Thirty-day cumulative mortality was 28.0% among current users compared with 21.6% among nonusers, yielding an adjusted hazard rate ratio (aHRR) of 1.02 (95% CI, 0.84–1.25). Compared with nonusers, the aHRR was 1.10 (95% CI, 0.87–1.40) for former users, 0.60 (95% CI, 0.29–1.21) for new users, and 1.06 (95% CI, 0.87–1.31) for long-term users. We observed no difference in the risk or outcome of CA-SAB with increasing ASA dose or by presence of diseases commonly treated with ASA. CONCLUSIONS: Use of ASA did not seem to influence the risk or outcome of CA-SAB. The apparent increased risk among new users may relate to residual confounding from the circumstances underlying ASA treatment initiation. Our finding of no association remained robust with increasing ASA dose and across multiple patient subsets.