Effects of nonadherence with prescription drugs among older adults.

OBJECTIVE To determine the association between prescription nonadherence and the health of older adults with 1 or more of 5 chronic conditions. STUDY DESIGN Analysis of the correlation between prescription nonadherence and the health of older adults. METHODS Data were from a 7-year panel with information on healthcare encounters and prescriptions. We used fixed-effects Cox duration regression models and fixed-effects Poisson count regression models to control for time-invariant factors specific to each subject when examining the impact of nonadherence on time to an emergency department (ED) visit (Cox regression) or number of ED visits (Poisson count regression). RESULTS Nonadherence was associated with subsequent ED visits for hypertension, chronic heart disease, diabetes, and hypercholesterolemia. No significant short-term effects of nonadherence on chronic obstructive pulmonary disease (COPD) were detected. However, long-term effects of nonadherence (using the count regression model with lagged counts) were detected for COPD, as well as for hypertension, diabetes, and hypercholesterolemia. CONCLUSIONS Medicinal adherence was important for all 5 conditions analyzed here. A year of nonadherence had the same correlation with ED use as making an older adult 1 year older.