Characterizing weekly self-reported antihypertensive medication nonadherence across repeated occasions

BACKGROUND Little is known about weekly variability in medication nonadherence both between and within persons. PURPOSE To characterize medication nonadherence across repeated, closely spaced occasions. METHODS This prospective cohort study comprised four unannounced telephone assessment occasions, each separated by approximately 2 weeks. On each occasion, adult outpatients taking at least a single antihypertensive medication completed a measure of extent of, and reasons for, nonadherence. RESULTS Two hundred and sixty-one participants completed 871 (83%) of 1,044 occasions. Nonadherence was reported on 152 (17.5%) of 871 occasions by 93 (36%) of 261 participants. The most commonly endorsed reasons for nonadherence were forgetting (39.5%), being busy (23.7%), and traveling (19.7%). Among 219 participants completing at least three occasions, 50% of the variability in extent of nonadherence was a result of within-person fluctuations, and 50% was a result of between-person differences. CONCLUSION Interventions to reduce nonadherence should be informed by variability in the extent of nonadherence and specific reasons for nonadherence.