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

Abstract

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.