Abstract 19486: Does the Association Between Adherence to Statin Medications and Mortality Depend on the Measurement Approach? A Retrospective Cohort Study
Background: Optimal adherence to statin medications is associated with reduced mortality rates. However, it is not clear if the estimated benefits of statin adherence are influenced by the method used to measure adherence.
Objective: To contrast the association between all-cause mortality and statin adherence when two different measurement approaches are used: (i.e., fixed summary measurement versus repeated measurement).
Methods: A retrospective cohort study was conducted using administrative data from Saskatchewan, Canada between 1994 and 2008. Eligible individuals received a statin prescription following discharge from a hospitalization for acute coronary syndrome (ACS). Adherence was measured using proportion of days covered (PDC) expressed either as: 1) a fixed summary measure, or 2) as a repeatedly measured covariate. Cox proportional hazards models were used to test the association between each adherence measure and mortality after covariate adjustment.
Results: Among 9,051 eligible individuals, optimal adherence (≥80%) modeled with a fixed summary measure was not associated with mortality (adjusted HR 0.97, 95% CI 0.86 to 1.09). In contrast, optimal adherence defined by the repeated measures approach was associated with a 25% reduction in the risk of death (adjusted HR 0.75, 95% CI 0.67 to 0.85).
Conclusions: Unlike summary measure, the repeated measures approach appears to provide a significant reduction of all-cause mortality of adherence to statins. This effect may be a result of the repeated measures approach being more sensitive, or more prone to survival bias. Therefore, we recommend comparing different measurement approaches whenever possible.
Author Disclosures: M. Alsabbagh: None. D. Eurich: None. L. Lix: None. T. Wislon: None. D.F. Blackburn: None.
- © 2015 by American Heart Association, Inc.