Polypharmacy induces side effects or drug interaction for elderly patients. Whether polypharmacy negatively affects stroke rehabilitation of patients is unclear in Japan. The aim of this study was to assess the relationship between polypharmacy and recovery of daily activity among convalescent stroke patients.

In this retrospective cohort study, we screened 719 stroke patients who were admitted to and discharged from the Sagami Rehabilitation Hospital or the Tsurumaki Onsen Hospital between April 2012 and July 2014 in Kanagawa, Japan. Among 719 patients screened, 509 were excluded because of propensity score matching. The primary outcome was Functional Independence Measure-Motor (FIM-M) effectiveness, and participants were divided according to FIM-M effective scores into the following two groups: non-improvement (105 patients) or improvement of FIM-M effectiveness (105 patients).

Risk factors associated with non-improvement of FIM-M effectiveness included epilepsy and number of drugs used upon admission. FIM-M effectiveness in the patients in whom five or more drugs were used upon admission was significantly lower than in those in whom one drug was used. Through this finding, we defined the use of five or more drugs as polypharmacy. Drugs with significant differences regarding polypharmacy included antihypertensive and antidiabetic drugs.

These findings suggested that polypharmacy negatively affects stroke rehabilitation outcomes. Thus, pharmacists should make attempts to respond to individual patient outcomes to optimize prescriptions, which may minimize the brunt of polypharmacy on patient outcomes.