Early-Life Height Attainment in Cystic Fibrosis Is Associated with Pulmonary Function at Age 6 Years

Rationale: In contrast to the well-described association between early-life weight for age, body mass index (BMI), and later lung disease in people with cystic fibrosis (CF), the relationship between height-for-age (HFA) percentiles and respiratory morbidity is not as well-studied. We hypothesized that changes in HFA in children with CF in the first 6 years of life would be associated with pulmonary function at the age of 6-7 years. Objectives: To determine if an association exists between changes in HFA in early life and pulmonary function in school-aged children with CF. Methods: We performed a retrospective longitudinal cohort study of children with CF followed in the CF Foundation Patient Registry who were born between 2003 and 2010, had CF diagnosed before the age of 2 years, and were followed through at least the age of 7 years. Changes in annualized HFA were classified into mutually exclusive categories. Multivariable analysis of covariance models were used to test for an association between the percent-predicted forced expiratory volume in 1 second (FEV₁) at the age of 6-7 years and height-trajectory categories. Results: There were 5,388 eligible children in the CF Foundation Patient Registry. The median (interquartile range) HFA at the age of 6-7 years was in the 39.5th (17.2th-64.9th) percentile. The mean (95% confidence interval) FEV₁% predicted at the age of 6-7 years was 95.6% (95.1-96.1%). In a multivariable regression model, the mean (95% confidence interval) FEV₁% predicted was higher for children with HFA that was always above the 50th percentile (97.8% [96.3-99.4%]) than for children whose height had been below the 50th percentile for at least 1 year and increased by ≥10 percentile points (95.1% [93.7-96.6%]), was stable (94.3% [92.8-95.7%]), or decreased by ≥10 percentile points (95.7% [94.2-97.3%]). The association between HFA categories and FEV₁% predicted was not affected by adding the mean annualized BMI percentile at the age of 6-7 years to the regression model. Among those with HFA that decreased by ≥10 percentile points, there was a correlation between the nadir annualized HFA percentile and the FEV₁% predicted at the age of 6-7 years. Conclusions: Children with CF with HFA that is always above the 50th percentile have the highest pulmonary function at the age of 6-7 years. Maintaining a BMI above the 50th percentile remains an important achievable goal for children with CF but is not the sole marker that should be examined in evaluating nutrition.