Background: Statins reduce cardiovascular morbidity and mortality after continuous treatment. Studies have shown that less than 50% of patients take 80% or more of prescribed doses 1 year after starting therapy.
Objective: To evaluate the impact of statin adherence on the incidence of coronary artery disease (CAD).
Methods: A cohort of 115,290 patients was reconstructed using the Régie de l'assurance maladie du Québec databases. Patients aged 45 to 85 years, without indication of cardiovascular disease (CVD), and newly treated with statins between 1999 and 2004 were eligible. A nested case-control design was used to study CAD. Every case was matched for age and duration of follow-up with randomly selected controls. The adherence level was measured by calculating the medication possession ratio. Rate ratios (RR) of CAD were determined through conditional logistic regression adjusted for several covariates.
Results: The mean patient age was 63 years, 54% had hypertension, 26% had diabetes, and 41% were males. The proportion of patients with high adherence level to statins (> or = 80%) was 74% during the first year and 53% after 1 year of follow-up. High adherence was associated with a risk reduction of 18% [RR: 0.82 (95% CI: 0.77-0.87)] compared to an adherence level of <20%. Developing a CVD during follow-up, being male, having been diagnosed with hypertension or diabetes, or having a high chronic disease score increased the risk of CAD.
Conclusion: Our study suggests that better adherence to statin agents is associated with a significant risk reduction of CAD. Adherence to statin agents needs to be improved so that patients can benefit from the full protective effects of statin therapies.