Proportion and risk indicators of nonadherence to statin therapy: a meta-analysis.

BACKGROUND Nonadherence to chronic disease medications is important. A growing body of literature suggests that better delivery of established therapies would save more lives than would discovery of innovations. Our first objective was to quantify the proportion of adherence to statin medications. The second objective was to provide estimates of risk indicators associated with nonadherence to statin medications. METHODS We performed a systematic literature review and meta-analysis of all studies published between database inception and June of 2011 that reviewed adherence, and risk indicators associated with nonadherence, to statin medications. RESULTS In the end, 67 studies met our inclusion and exclusion criteria and passed our methodological-quality evaluation. Among observational studies, 49.0% (95% confidence interval [CI], 48.9%-49.2%) of patients were adherent to statin medications at 1 year of follow-up. Among randomized trials, 90.3% (95% CI, 89.8%-90.8%) of patients were adherent to statin medications at 1 year of follow-up. The association between 147 variables and adherence to statin medications was determined. After meta-analysis, only 6 variables were associated with nonadherence to statin medications: primary prevention (rate ratio = 1.52; 95% CI, 1.50-1.53); new statin users (rate ratio = 1.46; 95% CI, 1.33-1.61); copayment (rate ratio = 1.28; 95% CI, 1.09-1.50; lower income status (rate ratio = 1.26; 95% CI, 1.16-1.37); fewer than 2 lipid tests performed (rate ratio = 1.38; 95% CI, 1.16-1.64), and not having hypertension (rate ratio = 1.16; 95% CI, 1.12-1.21). CONCLUSIONS This study provides some insight into the extent of nonadherence by study type along with 6 risk indicators associated with nonadherence to statin medications.