OBJECTIVETo study the association between body mass index (BMI) and lung function of asthmatic children after inhaling corticosteroids (ICS).

METHODSOne hundred and fifty-seven children with asthma were classified into obese (46 cases), over-weight (50 cases) and normal-weight groups (61 cases) based on BMI. All of the children received ICS for one year. Pulmonary functions were evaluated before and after treatment. Large airway function includes forced expiratory volume in one second (FEV1%) and forced vital capacity (FVC%). Small airway function includes maximal expiratory flow 25 (MEF25%) and maximal expiratory flow 50 (MEF50%).

RESULTSThe bronchial provocation test before treatment showed that the decline rate of pulmonary function (FVC%, FEV1%, MEF25% and MEF50%) in the obese group was higher than the normal-weight group after methacholine inhalation. After salbutamol inhalation, the improvement rate of the large airway (FVC%) and small airway (MEF25% and MEF50%) functions in the obese group was lower than the normal-weight group, and the improvement rate of small airway (MEF25% and MEF50%) function in the over-weight group was lower than in the normal-weight group. After treatment with ICS for one year, large airway function (FVC% and FEV1%) in the normal-weight group was higher than pre-treatment, however only FVC% in the normal-weight and obese groups was higher than pre-treatment. There was no significant difference in small airway function before and after treatment in all three groups.

CONCLUSIONSObesity can increase the sensitivity to methacholine and restrain the sensitivity to tosalbutamol in children with asthma. ICS can improve the large airway function in asthmatic children with normal body weight, but has no effect on small airway function. Obesity can restrain the effect of ICS on asthmatic children.