Body mass index status and peripheral airway obstruction in school-age children: a population-based cohort study

Background Few large prospective studies have investigated the impact of body mass index (BMI) on lung function during childhood. Methods Using data collected between 2002 and 2013, we analysed associations between BMI status and lung function (assessed by spirometry) from 8 to 16 years, as well as cross-sectional associations with small airway function (impulse oscillometry) at 16 years in the BAMSE cohort (n=2889). At 16 years, cross-sectional associations with local and systemic inflammation were investigated by analysing FE NO, blood eosinophils and neutrophils. Results Overweight and obesity at 8 years were associated with higher FVC, but lower FEV 1 /FVC ratio at 8 and 16 years. In boys, but not girls, obesity at 8 years was associated with a further reduction in FEV 1 /FVC between 8 and 16 years. In cross-sectional analyses, overweight and obesity were associated with higher frequency dependence of resistance (R 5-20) and larger area under the reactance curve (AX0.5) at 16 years. Increased blood neutrophil counts were seen in overweight and obese girls, but not in boys. No association was found between BMI status and FE NO. Persistent, but not transient, overweight/obesity between 8 and 16 years was associated with higher R 5-20 and AX0.5 and lower FEV 1 /FVC (-2.8% (95% CI -4.1 to -1.2) in girls and -2.7% (95% CI -4.4 to -1.1) in boys) at 16 years, compared with persistent normal weight. Conclusion I n childhood and adolescence, overweight and obesity, particularly persistent overweight, were associated with evidence of airway obstruction, including the small airways.