In Cystic Fibrosis, Early Childhood Weight-for-Age Affects Later Lung Function
In cystic fibrosis, weight at 1 year of age and weight-for-age trajectories across early childhood are associated with later pulmonary function.
In persons with cystic fibrosis (CF), weight at 1 year of age and weight-for-age trajectories across early childhood are associated with later pulmonary function, according to the study results published in the Journal of Cystic Fibrosis.
Understanding the effect of early-life nutritional and weight status changes over time on pulmonary function may help inform how nutritional assessment can guide clinical care in a pediatric CF population. Investigators therefore sought to characterize the link between weight-for-age trajectories in early childhood (ie, ages 1 to 5 years) and lung function at 6 years of age with the use of data from 2 national CF registries (the United Kingdom [UK] and Canadian CF Registries).
The researchers used a mixed effects linear regression model to describe children’s weight and BMI z-score trajectories between ages 1 and 5 years. The investigators then used the intercept (ie, weight-for-age at 1 year old) and slope (ie, weight-for-age trajectory) from this model as covariates in a linear regression of first pulmonary function measurement at 6 years of age.
A total of 1974 persons with cystic fibrosis from the UK Registry and 791 from the Canadian Registry were included in the analysis. Characteristics of the participants from both the UK and Canadian datasets were similar, apart from presentation at diagnosis. Nearly half (48%) of the UK Registry were asymptomatic at diagnosis, as opposed to 25.0% of the Canadian Registry. The percentage of persons with CF diagnosed by newborn screening was higher among those in the UK group as well.
Results of the study showed that in both the UK and Canadian registries, greater weight-for-age z-scores at 1 year of age and greater change in weight-for-age over time were associated with higher forced expiratory volume in 1 second (FEV1) percent predicted (UK Registry: 3.78%, 95% CI, 1.76-4.70; Canadian Registry: 3.20%, 95% CI, 1.76-4.70). These associations were replicated for BMI z-scores and forced vital capacity (FVC) percent predicted as well.
Evidence also demonstrated that children whose weight-for-age z-score increased over time had better pulmonary function at 6 years of age. A child with a slope of 0.07 z-scores per year (ie, the 75th percentile for weight-for-age z-score slopes in the UK) would be expected to have a higher percent predicted first FEV1 of 2.72, compared with a child with a slope of -0.08 (representing the 25th percentile).
The association between weight-for-age z-score at 1 year of age and FVC percent was similar to that of FEV1 percent. An increase of around 4.0 FVC percent was shown for each increase in z-score of weight-for-age at 1 year of age. In both datasets, a smaller association between weight-for-age increase over time (ie, slope) and FVC percent was observed.
Understanding the pulmonary impact of changes in early life nutritional status over time in a paediatric CF population may help inform how to use nutritional assessment to guide clinical care. The estimated associations using BMI z-score intercept and slope with the initial FEV1 percent and FVC percent were greater in magnitude compared with the analysis that utilized weight-for-age z-scores. An increase of 1 BMI z-score at 1 year of age was associated with an increase of 4.13 FEV1 percent (95% CI, 3.26-5.01) in the UK Registry and 3.70 FEV1 percent (95% CI, 2.02-5.41) in the Canadian Registry. Increasing BMI z-score over time was shown to be linked to greater FEV1 percent in the UK only (UK Registry: 1.96, 95% CI, 1.43-2.50; Canadian Registry: 0.68, 95% CI, –0.34 to 1.66).
Limitations of the present study include missing data, lack of routinely obtained lung function measures prior to 5.5 years of age, and the inability to differentiate between fat and fat-free mass in weight and BMI. “Understanding the pulmonary impact of changes in early life nutritional status over time in a paediatric CF population may help inform how to use nutritional assessment to guide clinical care,” said study authors. “Our findings provide evidence that early weight-for-age, specifically at age 1 year, and weight-for-age trajectories across early childhood are associated with later lung function, and that this relationship persists after adjustment for potential confounders,” study authors concluded. “Current guidelines may need to be updated to place less emphasis on a specific cut-off (such as the 10th percentile) and encourage clinical tracking of weight-for-age over time, as well as weight-for-age in early infancy” in the pediatric CF population, the researchers added. Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
References:Macdougall A, Jarvis D, Keogh RH, et al. Trajectories of early growth and subsequent lung function in cystic fibrosis: an observational study using UK and Canadian registry data. J Cyst Fibros. Published online September 7, 2022. doi:10.1016/j.jcf.2022.09.001