Rehabilitation Length of Stay, Body Mass Index, and Functional Improvement Among Adults With Traumatic Spinal Cord Injury

Objective: To examine the modifying effect of body mass index (BMI) on the association between rehabilitation length of stay (LOS), severity of injury, and motor FIM (mFIM) improvement in patients with traumatic spinal cord injury (TSCI). Design: Retrospective cohort study. Setting: Seventeen SCI Model Systems (SCIMS) centers in the United States. Participants: A total of 3413 patients (N=3413) who had a TSCI were admitted to an SCIMS between October 2011 and August 2018. Interventions: Not applicable. Main Outcome Measures: The mFIM (12 items) improvement by discharge. Four rehabilitation LOS groups split by quartiles were created for each neurologic severity of injury group (C1-C4 level with American Spinal Injury Association Impairment Scale [AIS] ABC, C5-C8 AIS ABC, T1-S3 AIS ABC, AIS DE). The interrelationship among rehabilitation LOS, BMI, and mFIM improvement were examined using multivariate linear regressions. A stratified analysis was performed to examine the association between rehabilitation LOS and mFIM improvement by BMI status (underweight or normal weight, overweight, obesity) and neurologic groups. Results: A total of 1099 (32.2%) and 821 (24.1%) patients were overweight and had obesity, respectively. Patients with obesity had less improvement in mFIM than those who were underweight or normal weight (unit of mFIM improvement, −3.71). After stratifying by BMI status, among patients with obesity, those with the longest rehabilitation LOS showed greater improvement in mFIM than those in the shortest LOS (unit of mFIM improvement=4.78). Conclusions: Longer inpatient rehabilitation LOS may benefit patients with TSCI by increasing mFIM improvement by discharge. Obesity is negatively associated with mFIM improvement.