Objective: Chronic conditions often require multiple medication intake. However, past research has focused on assessing overall adherence or adherence to a single index medication only. This study explored adherence measures for multiple medication intake, and in daily life, among patients with multiple chronic conditions (i.e. multimorbidity).
Design: Eighty-four patients with multimorbidity and multiple-medication regimens completed three monthly panel questionnaires. A randomly assigned subsample additionally completed a 30-day daily diary.
Main outcome measure: The Non-Adherence Report; a brief self-report measure of adherence to each prescribed medication (NAR-M), and in daily life. We further assessed the Medication Adherence Report Scale (MARS), and a subsample of participants were randomised to electronic adherence monitoring.
Results: The NAR-M indicated M = 94.7% adherence at Time 1 (SD = 9.3%). The NAR-M was significantly correlated with the MARS (rt1 = .52, rt2 = .57, and rt3 = .65; p < .001), and in tendency with electronically assessed adherence (rt2 = .45, rt3 = .46, p < .10). Variance components analysis indicated that between-person differences accounted for 10.2% of the variance in NAR-M adherence rates, whereas 22.9% were attributable to medication by person interactions.
Conclusion: This study highlights the importance and feasibility of studying adherence to multiple medications differentially, and in daily life. Future studies may use these measures to investigate within-person and between-medication differences in adherence.
Keywords: electronic medication adherence; multimorbidity; multiple chronic conditions; multiple medications; polypharmacy; self-report.