Changes in body mass index during childhood and risk of various asthma phenotypes: a retrospective analyse

Background It is known that asthma is related to obesity but also to small birth weight. The objective of the present study was to clarify this issue by assessing the putative relationship between the change between birth and childhood in child's corpulence as assessed by body mass index (BMI) and asthma phenotypes. Methods The following status in corpulence were assessed in 7781 schoolchildren using quartile of BMI at birth and at around 10 (9-11years): underweight at birth and at around 10, underweight at birth and overweight at around 10, overweight at birth and underweight at around 10, overweight at birth and at around 10 and the reference group constituted by all the other children in whom corpulence changes were not extreme. Determination of asthma phenotypes (allergic, non-allergic and exercise-induced asthma) was based on a clinical examination including skin prick tests, an exercise challenge test and a questionnaire. Results The risk of allergic asthma was higher in children with persistent underweight, children with persistent overweight and children becoming markedly more corpulent. In boys, the risk of allergic asthma was significantly higher for the less corpulent children at birth, regardless of whether they remained so or become overweight. In girls, the risk of allergic asthma was significantly higher in those with persistent overweight. There were no significant associations between BMI changes and non-allergic and exercise-induced asthma. Conclusions We observed that some extreme changes in BMI, persistent underweight and persistent overweight in childhood increased the risk of allergic asthma.