Background
Pharmacy refill adherence assesses medication-filling behaviors whereas self-report adherence assesses medication-taking behaviors. We contrasted the association of pharmacy refill and self-reported antihypertensive medication adherence with cardiovascular disease (CVD) incidence.
Methods and Results
Adults (n=2075) from the prospective Cohort Study of Medication Adherence among Older Adults (CoSMO) recruited between August 2006 and September 2007 were included. Antihypertensive medication adherence was determined using a pharmacy refill measure, Medication Possession Ratio-MPR (low, medium, high MPR: <0.5, 0.5 to <0.8, ≥0.8, respectively) and a self-reported measure, 8-item Morisky Medication Adherence Scale-MMAS-8 (low, medium, high MMAS-8: <6, 6 to <8, and 8, respectively). Incident CVD events (stroke, myocardial infarction, congestive heart failure, or CVD death) through February 2011 were identified and adjudicated. The prevalence of low, medium and high adherence was 4.5 %, 23.7%, and 71.8% for MPR and 14.0%, 34.3%, and 51.8% for MMAS-8. During a median 3.8 years follow-up, 240 (11.5%) people had a CVD event. After multivariable adjustment and compared to those with high MPR, the hazard ratios (HR) for CVD associated with medium and low MPR were 1.17 (95% confidence interval [CI] 0.87, 1.56) and 1.87 (95% CI: 1.06, 3.30), respectively. Compared to those with high MMAS-8, the HRs (95% CI) for MMAS-8 for medium and low MMAS-8 were 1.04 (0.79–1.38) and 0.89 (0.58–1.35), respectively.
Conclusions
Pharmacy refill but not self-report antihypertensive medication adherence was associated with incident CVD. The differences in these associations may be due to distinctions in what each adherence measure assesses.
