Strength of association between body mass index and physical function scores in paediatric burn patients: A National Institute on Disability, Independent Living, and Rehabilitation Research Burn Model System study

Objective: Increased body weight has been associated with reduced muscle wasting in the early catabolic phase after a severe burn. Yet, overweight and obese non-burn children often exhibit impaired musculoskeletal function, which may lead to poor physical function (PF). We aimed to determine the association between body mass index (BMI) at discharge and self-reported PF and caregiver proxy-reported PF during recovery of burned children. Materials and methods: This is a retrospective multisite longitudinal study in paediatric burn patients ((8–17 y old at time of burn). PF outcome measures were self-reported mobility, proxy-reported mobility, and upper extremity PF evaluated using PROMIS measures at 6-, 12-, and 24-months after injury. Primary exposure variable was BMI-for-age at discharge. Results: A total of 118 paediatric patients, aged 11.7 ± 3.3 y, with burns covering 37.6 ± 18.8% of their total body surface area (TBSA) and BMI-for-age of 23.1 ± 5.4 kg/m² at discharge were analyzed. BMI at discharge was not significantly associated with self-reported mobility scores 6 months after burn (beta coefficient =−0.23, p = 0.31), had a positive effect on mobility at 12 months (beta = 0.46, p = 0.05), and no effect at 24 months after injury (beta=−0.10, p = 0.60), when adjusted for burn size. BMI did not have a significant effect on proxy-reported mobility or upper extremity PF. Conclusion: A greater BMI at discharge was associated with improved self-reported PF at 12 months after burn but not at 6 months or 24 months, which suggests a faster recovery of PF in paediatric patients of larger body weight. Our data suggests that a larger body weight does not compromise the recovery of PF after burn.