Persistence of atorvastatin and simvastatin among patients with and without prior cardiovascular diseases: a US managed care study.

BACKGROUND: In clinical practice, persistence with statin therapy is poor. While little is known about relative persistence to specific statins, previous studies have observed greater persistence in patients who achieve greater degrees of lipid lowering. Identification of statin therapies which improve patient persistence has the potential to improve the quality of patient care and clinical outcomes. Therefore, we assessed patient persistence with atorvastatin and simvastatin in primary and secondary prevention patients enrolled in managed care.

METHODS: New statin users aged > or =18 years, both with and without prior cardiovascular (CV) events within the 12 month pre-treatment period, were identified from a large national database of managed care patients. Patients initiated atorvastatin or simvastatin therapy from January 1, 2003 to September 30, 2005 and were continuously enrolled in a covered plan for at least 12 months before and after initiation of statin therapy. Subanalyses of patients > or =65 years were also conducted. Measures of interest included demographic and clinical characteristics of the study samples and persistence of statin utilization over the 1-year follow-up period. Persistence was defined as the number of days a patient remained on treatment in the first year following their index date, measured from the date of first fill to study end or the date of discontinuation.

RESULTS: A total of 129 764 atorvastatin users and 45 558 simvastatin users without prior CV events were included in the study. For those patients with prior CV events, a total of 6888 atorvastatin users and 4443 simvastatin users were included in the study. Median persistence in patients without prior CV events was 50 days longer for patients initiating therapy with atorvastatin than simvastatin (207 vs. 157 days, p<0.0001) and after adjusting for confounding factors, those treated with atorvastatin were 15% less likely to discontinue therapy during the first year than those treated with simvastatin (HR=0.85; 95% CI 0.84, 0.86; p<0.001). In secondary prevention patients median persistence was 85 days longer in atorvastatin patients than simvastatin patients (266 vs. 181 days, p<0.0001) and atorvastatin patients were 22% less likely to discontinue therapy (HR=0.78; 95% CI 0.75, 0.82; p<0.001). Persistence was worse in the elderly patients, but the relative difference between atorvastatin and simvastatin was similar to the overall patient population.

CONCLUSIONS: In patients with and without prior CV disease, persistence is generally poor, even worse in the elderly, but significantly better for atorvastatin patients than simvastatin patients (p<0.001). Further studies are required to determine whether this is due to differences in cost, effectiveness, side-effects, or other attributes of the statins.

STUDY LIMITATIONS: Differences in persistence could be, in part, due to unmeasured confounders although all available variables were adjusted in multivariate analyses. Additionally, the claims database lacks some clinical data such as lipid levels, limiting assessments of statin efficacy, and does not include any reasons for discontinuation of therapy.