Background/Aims: The Hyperlink study is a cluster randomized trial in patients with uncontrolled blood pressure. The objectives of this analysis were: (a) to compare measures of self-reported adherence with actual adherence to medications at study enrollment (b) to study predictors of adherence.
Methods: We analyzed prescription claims data for 146 participants who had prescription coverage through HealthPartners for at least one year prior to study enrollment and were taking at least 1antihypertensive medication. Self-reported adherence was measured using a 4-item Morisky scale. Actual adherence was defined as a continuous measure of Medication Possession Ratio (MPR) as well as a binary measure defining adherence as an MPR of >80%.
Results: Of the 146 study participants, mean age was 66 (37-89 years), 14% were non-white, 48% were females, 45% had a 4yr college degree. Mean MPR was 0.86, 71% of patients were adherent by the binary MPR measure, and 70% self-reported high adherence (Morisky score=0). Higher self-reported adherence (lower Morisky score) was significantly associated with higher MPR (Pearson r=-0.4; p<0.001). Results of multiple linear regression showed that higher age (p=.04) and higher number of medications (p=0.04) predicted higher mean MPR. Race, gender and education were not associated with MPR. Higher self-reported adherence was associated with higher age but not race, gender, education, or number of medications.
Conclusions: Self-reported adherence was correlated with actual adherence in this sample of patients with uncontrolled blood pressure. Age and number of medications were important predictors of adherence. Our finding that patients on multiple drugs tend to be more adherent differs from many other studies, and may be related to the study population being sufficiently motivated to volunteer for a trial.