Key result
Optimal statin adherence measured using a repeated-measures approach was associated with a 25% reduction in mortality risk (HR 0.75), whereas a fixed summary measure showed no significant benefit.
Why the study?
Does the association between optimal statin adherence and mortality depend on the measurement approach (summary vs repeated-measures) in patients post-ACS?
Cohort (n=9,051)
Does the association between optimal statin adherence and mortality depend on the measurement approach (summary vs repeated-measures) in patients post-ACS?
Effect estimate: HR 0.75 (95% CI 0.67 to 0.85)
p-value: p=<0.01
The observed mortality benefit of optimal statin adherence in post-ACS patients depends heavily on the statistical approach used to measure adherence, highlighting the need for multiple measurement approaches in adherence research.
Adherence-mortality associations post-ACS vary by measurement method; leaves open optimal analytic strategies for future studies.
BACKGROUND: The aim of this study was to examine the relationship between mortality and statin adherence using two different approaches to adherence measurement (summary versus repeated-measures). METHODS: A retrospective cohort study was conducted using administrative data from Saskatchewan, Canada between 1994 and 2008. Eligible individuals received a prescription for a statin following 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. Multivariable Cox-proportional hazards models were used to estimate the association between adherence and mortality. RESULTS: Among 9,051 individuals, optimal adherence (≥80%) modeled with a fixed summary measure was not associated with mortality benefits (adjusted HR 0.97, 95% CI 0.86 to 1.09, p = 0.60). In contrast, repeated-measures approach resulted in a significant 25% reduction in the risk of death (adjusted HR 0.75, 95% CI 0.67 to 0.85, p < 0.01). CONCLUSIONS: Unlike the summary measure, the repeated measures approach produces a significant reduction of all-cause mortality with optimal adherence. This effect may be a result of the repeated measures approach being more sensitive, or more prone to survival bias. Our findings clearly demonstrate the need to undertake (and report) multiple approaches when assessing the benefits of medication adherence.
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Alsabbagh et al. (2017) conducted a cohort in Acute coronary syndrome (n=9,051). Statin adherence (repeated-measures approach) vs. Non-adherence (PDC < 80%) was evaluated on All-cause mortality (HR 0.75, 95% CI 0.67 to 0.85, p=<0.01). Optimal statin adherence measured using a repeated-measures approach was associated with a 25% reduction in mortality risk (HR 0.75), whereas a fixed summary measure showed no significant benefit.
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