Association between body mass index and functional independence measure in patients with deconditioning

OBJECTIVE: To assess the association of body mass index (BMI) with functional independence measure (FIM) score in patients with deconditioning. We also examined whether the association was different for motor and cognitive subscales of the FIM instrument. DESIGN: A retrospective study of 1077 inpatients admitted to the general medicine service for deconditioning at an acute rehabilitation hospital. Patients were classified into underweight (BMI < 18.5), normal range (BMI = 18.5-24.9), overweight (BMI = 25.0-29.9), obese class I (BMI = 30.0-34.9), obese class II (BMI = 35.0-39.9), and obese class III (BMI ≥ 40). RESULTS: Median gain in FIM scores from admission to discharge was highest in obese class I patients (27 points), followed by obese class II patients (26 points). The most gain in FIM scores was accounted for by the motor subscale. Adjusting for age, gender, and length of in-hospital stay, obese class I patients had a 5.8-point (95% confidence limits = 1.2, 7.0) higher gain in FIM score compared with patients with BMI in the normal range. CONCLUSIONS: In an acute rehabilitation setting, obese patients had higher gains in FIM scores as compared with normal-range-BMI patients. Most of the improvements in FIM scores were accounted for by the motor subscale, with little or no improvement on the cognitive scale.