Retrospective cohort study of medication adherence and risk for 30-day hospital readmission in a Medicare Cost Plan.

PURPOSE: Reducing hospital readmissions requires deploying appropriate interventions to groups at highest risk for readmission. Long-term medication adherence may indicate one's ability to manage recovery and chronic illness after discharge. If so, medication adherence also may be a predictor of hospital readmission. DESIGN: The objective of this study was to test the association of long-term medication adherence with hospital readmission in a cohort of beneficiaries enrolled in a Medicare Cost Plan. METHODOLOGY: The study employed a retrospective cohort design using administrative pharmacy and health care claims for a sample hospitalized in 2009. Medication adherence was measured with the medication possession ratio (MPR) for the 12 months prior to the first hospitalization in 2009. The likelihood of readmission within 30 days from the first hospitalization in 2009 was estimated using the logistic regression model. RESULTS: Long-term medication adherence was not associated with likelihood of 30-day hospital readmission (odds ratio [OR] = 0.82, P = .71). However, older age (OR = 1.07, P = .003) and longer length of hospital stay (OR = 1.2, P < .001) were associated with higher likelihood of 30-day readmission, while having an office visit within 30 days of discharge (OR = 0.38, P = .03) was associated with lower odds of readmission. CONCLUSION: Except for older age, variables associated with likelihood of readmission are difficult for clinical teams to access during a hospital stay to identify those at risk for readmission. Additional work is needed to identify indicators of readmission risk that can be utilized during hospitalization to identify patients needing post-discharge support to help prevent readmission.