Background: Several cross-sectional studies in patients with cystic fibrosis (CF) have shown that nutritional status and lung function are important determinants of peak aerobic capacity (peak oxygen uptake [V̇o2peak]). In order to account for individual changes, the aim of this study was to determine the longitudinal relationship of changes in nutritional status, lung function, and V̇o2peak in children with CF.
Design and methods: Fat-free mass (FFM), lung function, and V̇o2peak were assessed in 65 children with CF at baseline (mean ± SD age, 10.5 ± 2.9 years; mean FEV1, 92.6 ± 20.5%) and again 2 years later. FFM was calculated using skinfold thickness, and V̇o2peak was measured using an incremental treadmill test for children < 12 years old or an incremental cycle ergometry test for children ≥ 12 years old. Lung function was measured before the exercise test.
Results: Over the 2-year study period, an increase was found for absolute values of FFM (6.1 kg, p < 0.001), FEV1 (229 mL, p < 0.001), and V̇o2peak (240 mL, p < 0.001), while a decrease was found for predicted values of FEV1 (– 8.9%, p < 0.001) and V̇o2peak (– 4.4%, p < 0.05). ΔV̇o2peak over the 2-year period best correlated with ΔFEV1 (r = 0.619, p < 0.001) and to a lesser degree with ΔFFM (r = 0.506, p < 0.001). Multiple regression analysis demonstrated that ΔFEV1 and ΔFFM explained 47% of the variation of the ΔV̇o2peak over the 2-year period.
Conclusions: Our results show that longitudinal changes in V̇o2peak are associated with changes in lung function and to a lesser extent with changes in nutritional status in children with CF. Special consideration should be given to exercise training and nutritional intervention, which might improve long-term clinical outcome in children with CF.