Longitudinal Investigation of Older Adults' Ability to Self-Manage Complex Drug Regimens.

Objectives: We sought to investigate older patients' ability to correctly and efficiently dose multidrug regimens over nearly a decade and to explore factors predicting declines in medication self-management.

Design: Longitudinal cohort study funded by the National Institute on Aging.

Setting: One academic internal medicine clinic and six community health centers.

Participants: Beginning in 2008, 900 English-speaking adults, aged 55 to 74 years, were enrolled in the study, completing a baseline (T1) assessment. To date, 303 participants have completed the same assessment 9 years postbaseline (T4).

Measurements: At T1, subjects were given a standardized, seven-drug regimen and asked to demonstrate how they would take medicine over 24 hours. The number of dosing errors made and times per day that a participant would take medicine were recorded. Health literacy was measured via the Newest Vital Sign, and cognitive decline was measured by the Mini-Mental State Examination.

Results: Participants on average made 2.9 dosing errors (SD = 2.5 dosing errors; range = 0-21 dosing errors) of 21 potential errors at T1 and 5.0 errors (SD = 2.1 errors; range = 1-18 errors; P < .001) at T4. In a multivariate model, limited literacy (β = .69; 95% confidence interval [CI] = .18-1.20; P = .01), meaningful cognitive decline (β = 1.72; 95% CI = .70-2.74; P = .01), number of chronic conditions (β = .21; 95% CI = .07-.34; P = .01), and number of baseline dosing errors (β = -.76; 95% CI = -.85 to -.67; P < .001) were significant, independent predictors of changes in dosing errors. Most patients overcomplicated their daily medication schedule; no sociodemographic characteristics were predictive of poor regimen organization in multivariate models. In a multivariate model, there were no significant predictors of changes in regimen consolidation over time, except regimen consolidation at T1.

Conclusions: Older patients frequently overcomplicated drug regimens and increasingly made more dosing errors over 9 years of follow-up. Patients with limited literacy, cognitive decline, and multimorbidity were at greatest risk for errors. J Am Geriatr Soc 68:569-575, 2020.