Researchers at the University of Pennsylvania recently conducted a study to assess the association between body composition and pulmonary function in children and adolescents with cystic fibrosis (CF). By determining body composition through measuring body mass index (BMI), lean body mass (LBM), and fat mass (FM) researchers found that LBM could serve as a more accurate marker to determine pulmonary function than BMI — especially in under-nourished children and adolescents with CF.
LBM is a parameter for showing the weight of muscle, bones, and internal organs excluding body fat. BMI measures body fat in the individual, calculated by using the values of height and weight.
The methods that currently use BMI to determine pulmonary function in CF patients are already well established. However, these methods were developed with adults in mind, and were found to be more difficult to apply for children and adolescents with cystic fibrosis. As a result, researchers developed a new hypothesis suggesting that the association of higher BMI with better pulmonary function in CF reflects the impact of LBM upon respiratory muscle strength and physical well-being.
With these backgrounds, the researchers worked to assess the association of body composition (BMI-Z, LBMI-Z, and FMI-Z) and pulmonary function (FEV1%-predicted and FVC%-predicted).
In the study, 208 children (114 year-old males, 97 females between the ages of 5-21/ 72% had at least one ΔF508 CFTR mutation) with pancreatic insufficient CF recruited from the Cystic Fibrosis Centers at The Children’s Hospital of Philadelphia and 390 healthy controls were analyzed. Their BMI, lean body mass index (LBMI), and fat mass index (FMI) were determined by measuring their height and weight and employing dual x-ray absorptiometry. Researchers also measured FEV1% and FVC as parameters of pulmonary function.
They analyzed the data and found that LBMI and BMI showed significant association with FEV1%-predicted and FVC%-predicted, while FM did not. In addition, LBM is lower than one would expect for a given BMI. With these results, they concluded that LBM could be more useful to assess pulmonary function in subjects with lower BMI, such as under-nourished child and adolescent with PI-CF.
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