Longitudinal changes in lung function and somatic growth in children with sickle cell disease.

Background: We studied the changes in the patterns of lung function and somatic growth over time in children and adolescents (10.6 +/- 3.5 years at first test) with hemoglobin SS (Hb-SS) sickle cell disease (SCD).

Methods: Lung function and somatic growth were measured twice with an interval of 42.3 +/- 23.3 months in 45 children (25 females and 20 males) with Hb-SS SCD.

Results: The lung volumes slightly decreased but remained borderline normal in both tests. All spirometric indices were within the normal range but significantly decreased (P<0.001) at the time of the second test indicating development of lower airway obstruction (forced expiratory volume in the first second (FEV(1)): 87 +/- 21 vs. 80 +/- 15; FEV(1)/forced vital capacity (FVC): 89 +/- 7 vs. 85 +/- 6; FEF(25-75): 89 +/- 32 vs. 76 +/- 24). "Normal" pattern of lung function was initially found in 56% of the patients, but in only 29% in the second test. In contrast, those with "obstructive" pattern increased from 22 to 44%, and those with "restrictive" pattern from 22 to 27%. There was no association between history of asthma and pattern of lung function. "Normal" Body Mass Index (BMI) was found in 64% of the patients, whereas 13% had "High" BMI and 22% "Low" BMI. The two latter patterns were associated with abnormal lung function but only patients with normal BMI showed actual decline overtime.

Conclusion: SCD is characterized by a predominantly obstructive pattern of lung function that increases in prevalence over time. There was no apparent causal relationship between the pattern of somatic growth and the pattern of lung function.