Among 8928 post-menopausal women with cardiovascular disease, 4101 (46%) reported taking aspirin. Of the aspirin users, 1224 (30%) were on 81mg and 2877 (70%) were on 325mg. Among women with a history of myocardial infarction, transient ischemic attack, prior revascularization, stroke, and angina the rate of aspirin use was 54%, 43%, 50%, 71% and 44%, respectively. Baseline characteristics according to aspirin use and dose are summarized in .
Baseline Differences for Women With Cardiovascular Disease According to Aspirin Dose
Predictors of Aspirin Use and Dose
Clinical predictors of aspirin use included prior revascularization (3.08 [2.68-3.55]), hypercholesterolemia (1.27 [1.10-1.46]), treated hypertension (1.18 [1.05-1.33]), previous MI (1.18 [1.04-1.33]), prior transient ischemic attack (1.41 [1.23-1.61]), statin treatment (1.40 [1.19-1.65]) and beta blocker therapy (1.54 [1.36-1.74]). Demographic predictors of aspirin use included increasing age per year (1.02 [1.01-1.03]) and college education (1.25 [1.01-1.55]). Negative predictors of aspirin use included African American race (0.70 [0.59-0.83]), Medicaid insurance (0.59 [0.45-0.77]), increasing BMI (0.98 [0.98-0.99]) and NSAID use (0.86 [0.76-0.97]).
Women who were older and more educated were more frequently on 81mg. A history of myocardial infarction, prior revascularization, beta blocker use and increasing BMI were predictors for 325mg. Race and insurance type were not associated with aspirin dose.
Aspirin Use, All-Cause Mortality and Cardiovascular Outcomes
During an average of 6.5 years of follow-up, 956 participants (10.7%) died. summarizes all outcomes based on aspirin use and dose. After multivariable adjustment, aspirin was associated with a 14% lowering in the risk of all cause mortality (HR 0.86 [0.75-0.99]) (). A composite of adverse cardiovascular events occurred in 969 (10.8%) women during follow-up. After multivariable adjustment, aspirin was associated with a non-significant decrease in cardiovascular events (HR 0.90 [0.78-1.04]). However, aspirin was associated with a 25% significantly lower risk of cardiovascular mortality (HR 0.75 [0.60-0.95]).
Clinical Outcomes According to Aspirin Use and Dose
Adjusted Cox Proportional Hazards Analyses of Time to Adverse Outcomes among Women with Cardiovascular Disease (n=8,928)
Several characteristics of the participants were examined for possible interaction with the use of aspirin and the risk of all-cause mortality (). No significant interaction was observed between age, race, smoking status, statin use, beta-blocker use and NSAID use. Women on current hormonal therapy appeared to have the greatest mortality benefit with aspirin therapy (P for interaction < 0.01). Possible interaction with aspirin use and the composite of adverse cardiovascular events were also assessed (). For women between the ages 50 to 59, 60 to 69, and 70 to 79, the hazard ratios for the composite of adverse cardiovascular events associated with age were 1.09, 1.01, and 0.77, respectively (P for interaction = 0.02).
Subgroup Analyses According to Aspirin Use
Aspirin Use in Propensity-Matched Patients
In order to better adjust for the baseline imbalances between groups, patients were matched on the basis of propensity score for aspirin use in a 1-to-1 fashion. This limited the analysis to 5,292 patients. These patients were well matched on the basis of baseline characteristics with no significant differences between users and non-users of aspirin (data not shown). illustrates survival curves in both groups. Overall, there were 565 deaths (10.7%). Aspirin use was associated with a significantly lower all-cause mortality (9.8% vs. 11.5%, P=0.045). Aspirin use was associated with a lower composite of cardiovascular adverse events, which was not statistically significant (10.1% vs. 11.3%, P=0.142). For the individual endpoints, aspirin therapy was associated with a significantly lower cardiovascular mortality with no significant lowering in the risk of myocardial infarction or stroke.
Clinical Outcomes According to Aspirin Use
Aspirin Dose in Propensity-Matched Patients
To investigate aspirin dose, a second propensity analysis was performed. We matched 1036 users of 81mg to 1036 users of 325mg. Baseline variables were similar between groups (data not shown). illustrates survival curves in both groups. No significant difference in mortality or cardiovascular events was noted between 81mg and 325mg patients.
Clinical Outcomes According to Aspirin Dose