A retrospective cohort study evaluating the relationship between statin medication adherence and economic outcomes in commercial health plans

Chanadda Chinthammit, David R. Axon, Seth Anderson, Breanne Lott, Ann M. Taylor, Matthew Pickering, Heather Black, Terri Warholak, Patrick J. Campbell

Abstract

Background: Adherence to statin medications is suboptimal; however, the association of statin adherence, as defined in medication adherence quality measures, with healthcare service use and expenditure within one year has not been assessed in a commercially insured United States (US) population.

Objective: To investigate the relationship between statin adherence, as specified in the Pharmacy Quality Alliance (PQA) statin medication adherence quality measure, and healthcare resource utilization and expenditures within commercial health plans over a one-year period.

Methods: This one-year retrospective analysis involved a cohort of individuals from the Truven Health MarketScan Commercial Claims and Encounters Research Databases (2009-2015). Generalized linear models with log link and negative binomial distribution (use) or gamma distribution (expenditures) were used to assess relationships between medication adherence (≥80% proportion of days covered) and healthcare use and expenditures (adjusted to 2015 US dollars) while adjusting for covariates. Beta coefficients were used to compute cost ratios (CR) and rate ratios (RR). An alpha level of 0.001 was set a priori.

Results: Of 4,450,308 eligible individuals, 2,757,288 (61.9%) were classified as adherent. Multivariable analyses indicated adherent individuals had more outpatient (RR = 1.009, 95% CI = 1.007, 1.010) and fewer inpatient visits (RR = 0.756, 95% CI = 0.749, 0.762); and lower outpatient (CR = 0.965, 95% CI = 0.963, 0.967), inpatient (CR = 0.780, 95% CI = 0.779, 0.782), and total expenditures (CR = 0.975, 95% CI = 0.973, 0.977). Adherence was associated with lower per member per month total healthcare expenditures ($18.91) vs nonadherence.

Conclusion: Within one year, statin adherence was associated with more outpatient and fewer inpatient visits, lower outpatient and inpatient expenditures, and lower total expenditures than nonadherence, within a commercially-insured population.