Factors Associated With Adherence to Statin Medications of Patients Enrolled in a Self-insured University Health Plan

The purpose of this study was to examine the association of patient and prescription factors with statin adherence of patients enrolled a self-insured university health plan.

We conducted a retrospective, longitudinal analysis of pharmacy claims data from a self-insured university for those enrollees prescribed a statin during a 38-month period (2009-2012). Adherence was calculated as the portion of days covered and was defined as portion of days covered ≥80%. To be included in the study, patients had to have ≥2 statin claims and be continuously enrolled in the plan. A logistic regression model was constructed to identify longitudinal predictors of adherence. In addition, a Cox proportional hazards model was run to examine predictors of adherence during 1year of statin therapy.

There were 222 patients in the study. These 222 patients generated a total of 3,349 statin claims. With a mean (SD) observation period of 970 (346.5) days, those patients taking statin medications had a mean adherence rate of 54.5%. Adherent and nonadherent patients were similar regardless of statin switching and inferred household income. However, those patients with greater adherence levels were older, more likely to be male, had previous statin exposure, paid higher mean copayments, and were more likely to use mail order as their delivery channel. In logistic regression, older age (odds ratio [OR] = 1.07, P = 0.001), male sex (OR = 1.79, P = 0.047), and the use of mail order (OR = 3.07, P = 0.002) were significantly associated with adherence. Of the original 222 patients, 200 patients completed 1 full year of therapy. In a subsequent Cox proportional hazards analysis, the retail delivery channel (hazard ratio = 1.904, P = 0.025) was associated with higher risk for nonadherence during a 1-year period.

Despite the benefits associated with statin medications, adherence remains a challenge for certain groups of patients, including patients who are female, younger patients, and patients who use retail pharmacies (vs mail order) when filling their prescriptions. Health care professionals and employers, especially those employers who are self-insured, would be well served in developing adherence interventions aimed at these specific populations.