Incorporating Behavioral Science in Medication Adherence Communication: A Randomized Clinical Trial

Hypertension increases the risk of myocardial infarction and strokes, but adherence to antihypertensive medications remains suboptimal. Increasing medication adherence may help prevent hypertension-related disability and death.

To estimate the effect of incorporating behavioral science principles in mailed communications intended to increase hypertension medication adherence.

This randomized clinical trial was conducted from August 18 to December 31, 2023, at Humana, a large health insurance provider, and included Medicare Advantage beneficiaries aged 65 to 80 years who were taking hypertension medications with adherence rates of 60% to 85%. Data were extracted for the as-treated analysis on April 14, 2024.

Study participants were randomized in equal proportions to 1 of 7 groups: 6 received mailed communications that incorporated combinations of behavioral science principles, and 1 received no mailing (control, or usual care condition). The specific principles included were social norming (the mailing noted that more Humana beneficiaries each year were improving their medication adherence scores), messenger effects (the mailing signatory was a pharmacist), and processing fluency (the mailing incorporated a visual circle metaphor indicating current and complete adherence to prompt "closing the ring"). The first mailing contained the participant's baseline refill score, and a second mailing noted any changes in the participant's refill score after 60 days.

The primary outcome was end-of-year hypertension medication adherence calculated from pharmacy claims data using the proportion of days covered (PDC) metric (having medication available for 1 target hypertension drug, as measured through prescription claims, counted as adherent on a given day). A secondary outcome was the proportion of study participants with end-of-year PDC of 80% or greater.

The study participants (n = 64 290) had a mean (SD) age of 71.4 (4.1) years, and 54.1% were female. Mean (SD) end-of-year adherence in the control group was 0.81 (0.12) and was no different in any of the intervention arms (absolute mean difference compared with control was 0.00 [95% CI, -0.01 to 0.01]). The proportion of participants with an end-of-year PDC greater than 80% also did not differ significantly between the control group (6587 of 9183 [71.7%]) and any of the intervention arms (range, 6467 of 9180 [70.4%] to 6598 of 9177 [71.9%]).

In this randomized clinical trial, use of social norms, messenger effects, and processing fluency in mailed communications did not significantly increase hypertension medication adherence. Further research is needed to identify tactics to effectively increase adherence.

ClinicalTrials.gov Identifier: NCT06066541.