Aspirin adherence, aspirin dosage, and C-reactive protein in the first 3 months after acute coronary syndrome

Persistent elevation of inflammatory markers such as C-reactive protein (CRP) has been associated with an increased risk of recurrent cardiac events after acute coronary syndromes (ACS). Conflicting evidence is available regarding whether aspirin can reduce CRP after ACS. We investigated whether the dosage and adherence to aspirin was associated with the CRP level 3 months after ACS. Adherence to aspirin was monitored for 3 months in a cohort of 105 patients enrolled within 1 week of an ACS using an electronic chip stored in the pill bottle cap. The CRP level was measured at baseline and 3 months. Logistic regression analysis was used to test whether poor adherence to aspirin and a lower aspirin dosage were associated with increased CRP levels, controlling for age, ACS type, disease co-morbidity, baseline CRP level, use of clopidogrel and statins, depressive symptoms, smoking, and adherence to other medications. Aspirin adherence was inversely correlated with the CRP level at 3 months (Spearman's r = -0.36, p < 0.001). In the adjusted model, every 10% decrease in aspirin adherence was associated with a 1.7 increased risk (95% confidence interval 1.2 to 2.4) of a CRP level of ≥ 3.0 mg/L at 3 months. Low-dose aspirin was associated with a 7.1 increased risk (95% confidence interval 1.5 to 33.3) of a CRP level of ≥ 3.0 mg/L. The Charlson co-morbidity index, depressive symptoms, and baseline CRP level were also predictive of a CRP level of ≥ 3.0 mg/L at 3 months. The association between aspirin adherence and CRP level was not attenuated by controlling for other risk-reducing behaviors. In conclusion, a strong association was found between aspirin adherence and the CRP level after an ACS.