Body composition and pulmonary function in cystic fibrosis.
BACKGROUND
Lower body mass index (BMI) is associated with worse pulmonary function in cystic fibrosis (CF).


OBJECTIVE
lean body mass (LBM) is more strongly associated with pulmonary function than BMI is.


METHODS
Anthropometrics, body composition by dual x-ray absorptiometry, and pulmonary function were determined in pancreatic insufficient CF (PI-CF) youth. Sex and age-adjusted Z-scores (BMI-Z, LBMI-Z, FMI-Z) were generated for CF and controls. (1) Associations of BMI-Z with LBMI-Z and FMI-Z and (2) age-adjusted associations of BMI-Z, LBMI-Z, and FMI-Z with FEV1%-predicted were tested.


RESULTS
Two hundred eight PI-CF subjects had lower BMI-Z, LBMI-Z, and FMI-Z compared to 390 controls. BMI-Z was associated with lower LBMI-Z (p < 0.0001) in PI-CF. In females, LBMI-Z and BMI-Z were positively associated with FEV1%-predicted; this relationship did not persist for FMI-Z after adjustment for LBMI-Z. In males, only LBMI-Z and BMI-Z were associated with FEV1%-predicted.


CONCLUSIONS
In PI-CF youth, deficits in LBM were apparent. At lower BMI percentiles, BMI may not accurately depict LBM in PI-CF. In under-nourished PI-CF youth, this preservation of FM in preference to LBM is relevant since LBMI-Z, but not FMI-Z, is positively associated with FEV1%-predicted. Lean body mass index is more strongly associated with lung function compared to BMI, especially in the under-nourished child and adolescent with PI-CF.
Division of Pulmonary Medicine, Cystic Fibrosis Center, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA ; Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA.
Saba
S
Sheikh
Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA ; Division of Gastroenterology, Hepatology and Nutrition, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA.
Babette S
BS
Zemel
Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA ; Division of Gastroenterology, Hepatology and Nutrition, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA.
Virginia A
VA
Stallings
Division of Pulmonary Medicine, Cystic Fibrosis Center, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA ; Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA.
Ronald C
RC
Rubenstein
Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania , Philadelphia, PA , USA ; Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia , Philadelphia, PA , USA.
Andrea
A
Kelly
body mass index; fat mass index; lean body mass; lean body mass index; pancreatic insufficient