* Compared with control, P<0.05;

† Compared with mild asthma, P<0.05;

‡ Compared with moderate asthma, P<0.05;

§ Compared with severe asthma, P<0.05.

Multiple-group comparisons were made by using one-way ANOVA, Bonferroni correction was applied to adjust for multiple comparisons.

Abbreviation: FEV₁: forced expiratory volume in one second; FVC: forced vital capacity; MMEF: maximal mid-expiratory flow; ICS: inhaled corticosteroid.