Background: Evidence from meta-analyses shows that statin therapy reduces all-cause mortality and nonhemorrhagic strokes. Nonadherence to statins may reduce this protective effect. The association between statin adherence and incidence of cerebrovascular disease remains unexplored outside the context of clinical trials.
Objective: To evaluate the impact of statin adherence on the occurrence of cerebrovascular disease in a real clinical setting.
Methods: A cohort of 112,092 patients was reconstructed using the Régie d'assurance maladie du Québec and Med-Echo databases. The Régie d'assurance maladie du Québec database contains information from 3 types of health-related data, such as demographic information, medical data, and the prescription claims file. The Med-Echo database contains data on acute care hospitalizations on all Quebec residents. All patients without cardiovascular disease aged 45-85 years who were newly treated with statins between 1999 and 2004 were eligible. A nested case-control design was used to study the occurrence of cerebrovascular disease. Adherence level was reported as a medication possession ratio. Conditional logistic regression models were used to estimate the rate ratio of cerebrovascular disease, adjusting for different covariables.
Results: The mean patient age was 63 years; 49% had hypertension, 21% had diabetes, and 41% were males. Nonadherence was prevalent because only 55% of the patients were exposed to > or = 80% of the medication during follow-up. We did not observe any major differences, defined as more than 5%, between the groups, except for the sex, diabetes, and hypertension. High level of adherence to statins was associated with a reduction of cerebrovascular events (rate ratio: 0.74; 95% confidence interval, 0.65-0.84).
Conclusions: Our study suggests a relatively low level of adherence to statins, but more importantly, that adherence is associated with a risk reduction for cerebrovascular disease. Adherence to statin therapy needs to be improved, so that patients can benefit from the full protective effects of statin therapy.