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 (beta = .69; 95% confidence interval [CI] = .18-1.20; P = .01), meaningful cognitive decline (beta = 1.72; 95% CI = .70-2.74; P = .01), number of chronic conditions (beta = .21; 95% CI = .07-.34; P = .01), and number of baseline dosing errors (beta = -.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.