Association between body composition and pulmonary function in children and young people with cystic fibrosis.

OBJECTIVES

Body mass index (BMI) has significant limitations when assessing nutritional status in pediatric patients with cystic fibrosis (CF). We evaluated whether measurements of lean body mass (LBM) and fat mass (FM) are more sensitive nutritional parameters by testing their association with pulmonary function in adolescent patients with CF.

METHODS

Sixty-nine male and female adolescents with CF were studied (age: 14.5 ± 2.3, BMI: 19.5 ± 2.3 kg/m). Dual-energy x-ray absorptiometry (DXA) was used to measure total and segmental (appendicular, truncal) body composition (FM, LBM bone mineral density, and content) as routine care to monitor bone health. Correlation and multiple regression analyses were performed to assess the association among body composition variables and forced expiratory volume in 1 s (FEV). We also evaluated the influence of the F508del mutation on body composition.

RESULTS

FEV was significantly associated with total (r = 0.68, P <0.001), truncal (r = 0.71, P <0.001), and appendicular (r = 0.67, P <0.001) LBM, whereas it was not associated with total (r = 0.02, P = 0.89) and truncal (r = 0.04, P = 0.77) FM. BMI had a significant but weaker correlation with FEV (r = 0.52, P <0.001) compared with LBM. LBM was the only significant predictor of FEV in fully adjusted regression models.

CONCLUSIONS

LBM is a significant predictor of pulmonary function in CF adolescent patients. DXA scanning performed as part of routine bone health monitoring in CF can provide important body composition data relevant to clinical interventions that optimize nutritional status. DXA reference data for LBM in non-adult populations are needed to enhance diagnostic assessment and monitor clinical progression of CF.