Rapid early increase in BMI is associated with impaired longitudinal growth in children with cystic fibrosis

Abstract

Background: We aimed to assess whether final height in children with cystic fibrosis (CF) is affected by body mass index (BMI), BMI increase, pulmonary function, and cystic fibrosis-related diabetes (CFRD). Study design: A longitudinal, retrospective study was performed in a cohort of 57 patients with CF (30 boys, 27 girls) born between 1997 and 2001. Height and weight were recorded annually from ages 0.5 to 10 years and biannually up to the age of 18. Measurements were converted to height-for-age-adjusted-for-target-height (HFA-TH) and BMI-for-age z-scores. Analyses were performed using the independent t tests and the Pearson's correlation. Results: For both boys and girls, HFA-TH and BMI-for-age z-scores were significantly lower in the first year of life, these scores increased rapidly until the age of 11 and 8 years, respectively. In boys, HFA-TH z-scores declined during puberty, with subsequently significantly impaired final height (z-score, −0.56, n = 30, standard deviation [SD] = 0.81, P = 0.001). In girls, HFA-TH z-scores briefly declined after the age of 8 years, but then increased to a z-score of −0.21 (n = 27, SD = 0.87) at age 18, which is not significantly lower than the national average (P = 0.22). Pulmonary function and the presence of CFRD were not associated with final height. However, rapid BMI increase between ages 1 and 6 was negatively associated with final height in boys (n = 29, r =−0.420; P = 0.023) and girls (n = 25, r =−0.466; P = 0.019). Conclusions: In boys and girls, early BMI increase was associated with impaired final height. We suggest that early childhood serves as a “window” in which nutritional variations may program subsequent growth. Further refinement of nutritional strategies could be needed.