In cystic fibrosis, above-average height in early life tied to highest pulmonary function

Children with cystic fibrosis and a height-for-age consistently above the 50th percentile had the highest pulmonary function at age 6 to 7 years, according to new data published in the Annals of the American Thoracic Society.

“The relationship between height-for-age and respiratory morbidity and mortality is not as well studied as the association between BMI and cystic fibrosis lung disease,” Don B. Sanders, MD, MS, associate professor of pediatrics in the division of pulmonology, allergy and sleep medicine at Indiana University, and colleagues wrote. “Children with cystic fibrosis with short stature have worse lung disease and a higher risk for early mortality.”

The retrospective, longitudinal cohort study included 5,388 children with cystic fibrosis who were born from 2003 to 2010 and followed in the Cystic Fibrosis Foundation Patient Registry. All children had a cystic fibrosis diagnosis before age 2 years and were followed until age 7 years. Researchers classified annualized height-for-age changes as consistently above the 50th percentile or annualized height-for-age with at least 1 year below the 50th percentile that increased or decreased by at least 10 percentile points or was stable.

In the cohort, the median height-for-age when the children were aged 6 to 7 years was in the 39.5th percentile and mean FEV₁ percent predicted was 95.6%. Researchers reported a higher mean FEV₁ percent predicted among children with a height-for-age that was consistently above the 50th percentile (97.8%) compared with children with height-for-age below the 50th percentile for at least 1 year and increased by at least 10 points (95.1%), decreased by at least 10 points (95.7%) or was stable (94.3%), according to the results.

The association between height-for-age categories and FEV₁ percent predicted was unaffected by adding the mean annualized BMI percentile when children were aged 6 to 7 years, according to the researchers.

Among children with a height-for-age that decreased at least 10 points, there was no correlation between the annual height-for-age percentile and the FEV₁ percent predicted at age 6 to 7 years, according to the results.

Studies that assess additional interventions to promote linear growth in this population are needed.

“Maintaining a BMI above the 50th percentile remains an important achievable goal for children with cystic fibrosis, but the results reported here can serve as a reminder that BMI is not the sole marker that should be examined in evaluating nutrition,” the researchers wrote.