Body composition and pulmonary function in cystic fibrosis.

Saba Sheikh,Andrea Kelly,Virginia A Stallings,Ronald C Rubenstein,Babette S Zemel

doi:10.3389/fped.2014.00033

Abstract

Background: Lower body mass index (BMI) is associated with worse pulmonary function in cystic fibrosis (CF). Hypothesis: 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.Conclusion: 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.

Highlights

Stature, weight, and body mass index (BMI) are typically used to assess nutritional status in cystic fibrosis (CF) since these measures are obtained in clinical practice and reference data are available
Results:Two hundred eight pancreatic insufficient CF (PI-CF) subjects had lower BMI-Z, LBMI-Z, and FMI-Z compared to 390 controls
LBMI-Z and BMI-Z were positively associated with FEV1%-predicted; this relationship did not persist for FMI-Z after adjustment for LBMI-Z

Summary

Introduction

Weight, and body mass index (BMI) are typically used to assess nutritional status in cystic fibrosis (CF) since these measures are obtained in clinical practice and reference data are available. Adults with unrecognized FFM depletion, defined as normal BMI and low FFM, have lower FEV1%-predicted than adults with both normal BMI and normal FFM [12] This finding highlights the limitation of BMI as an informative marker of nutritional status in complex chronic diseases such as CF [5]. Their study found that girls with PI-CF had a significantly lower fat mass (FM) compared to age-, height-, and puberty-matched controls, and that FM was positively associated with FEV1%-predicted. This association was not significant in males and no association was seen with FFM in this cohort. Hypothesis: lean body mass (LBM) is more strongly associated with pulmonary function than BMI is

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