The association between polypharmacy and the efficiency of the functional independence measure in an acute-stage hospital: a retrospective cohort study.

BACKGROUND The Functional Independence Measure (FIM) evaluates the activities of daily living (ADL), and FIM efficiency represents daily improvement in FIM. Polypharmacy affects both ADL and FIM; however, few studies have evaluated its relationship with FIM efficiency. AIM This retrospective study investigated the effect of polypharmacy on FIM efficiency in patients undergoing rehabilitation at our acute care hospital in 2014. METHODS We collected data on the patients' age, sex, diagnosis, length of hospital stay, type and duration of rehabilitation, indications for rehabilitation, FIM score before and after rehabilitation, and number of pharmaceuticals being used. Polypharmacy was defined as the administration of five or more pharmaceuticals. Using propensity score matching, we compared the FIM efficiency between the polypharmacy and non-polypharmacy groups (sub-scales and totals). RESULTS A total of 2455 patients were included. The analytical population included 2168 patients. The analytical population used for propensity score matching included 727 patients in each group (total: 1454 patients). The following FIM sub-scale items were found to be associated with significantly low FIM efficiency in the polypharmacy group: self-care (polypharmacy group FIM efficiency: 0.43 points/day, non-polypharmacy group FIM efficiency: 0.54 points/day) and sphincter control (0.11 points/day and 0.18 points/day, respectively). No significant differences in the FIM efficiency were observed either for any other sub-scales or for totals. DISCUSSION In the polypharmacy group, self-care and sphincter control, in particular, were associated with inhibited improvement in ADL and FIM. CONCLUSIONS Reducing polypharmacy among acute-phase patients would allow an earlier return to their normal daily lives.