Assessing adherence to multiple medications and in daily life among patients with multimorbidity

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 (r(t1)=.52, r(t2)=.57, and r(t3)=.65; p<.001), and in tendency with electronically assessed adherence (r(t2)=.45, r(t3)=.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.