Abstract 030: Aspirin Use and Myocardial Infarction in HIV versus Non-HIV Patients

Abstract

Introduction: Myocardial infarction (MI) risk is increased among HIV populations, but the use of aspirin (ASA) for primary prevention of MI has not been investigated in this group. Hypothesis: We hypothesized that ASA use would be associated with a decreased risk of incident MI in both HIV and matched control patients. Methods: Patients who received care from the Partners HealthCare System in Boston between 2000 and 2009 without baseline coronary heart disease (CHD) were included. Non-HIV patients were matched to HIV patients by demographic factors, with 33,348 control and 3,698 HIV patients. To ascertain non-episodic ASA use, we developed an algorithm combining medication data and electronic health record free text search and validated it using medical record review. We used a definition of at least two ASA prescriptions, two text strings, or one of each, all occurring more than 30 days prior to MI (sensitivity 73%, specificity 83%, AUC 78%). We used Cox proportional hazard modeling to assess the association between ASA use and first MI within the HIV and control groups. We further assessed the effect of ASA in models stratified by cardiovascular risk (low CHD risk = 0-1 traditional risk factors, high CHD risk = 2 or more risk factors), to minimize potential confounding by indication. Results: ASA use was significantly lower in HIV compared to non-HIV patients in the overall groups (12.4% vs. 15.3%, p<0.001) and among men (13.1% vs. 17.3%, p<0.001) but not among women. The relative difference in the rates of ASA use between HIV and non-HIV was greater among patients at high CHD risk (22.1% vs. 42.4%, p<0.001) compared to patients at low CHD risk (5.5% vs. 6.7%, p=.037). Similar patterns were seen within each gender. In multivariate models adjusting for CHD and HIV-related factors, ASA use was not associated with decreased MI risk among HIV patients overall (HR 0.97, 95% confidence interval [CI] 0.64-1.49, p=0.90), by CHD risk category or by gender. In contrast, ASA use was associated with significantly decreased MI risk in the non-HIV group in models adjusted for traditional CHD risk factors, with a reduced hazard of 71% (95% CI: 66%-76%). Relative risk reduction for MI in the non-HIV group was more pronounced among patients with high underlying CHD risk (71% vs. 57% in low CHD risk) and among males (76% vs. 50% in females). Conclusions: ASA use was relatively lower in HIV compared to matched control patients, particularly among those with high underlying CHD risk. In contrast to non-HIV patients for whom ASA was significantly associated with decreased MI risk, ASA did not show this effect among HIV patients. Further studies will help to establish whether patients with HIV disease may represent a subgroup in which ASA is less effective for primary prevention of MI.