Influence of body mass index on the response to asthma controller agents

The incidence of asthma has been positively associated with obesity. Asthma comprises diverse "phenotypes" reflecting heterogeneity in a number of characteristics, including response to therapy. The present authors examined whether body mass index (BMI) influenced the response to placebo, as well as to two asthma controller medications. A post hoc analysis was performed, pooling data from four double-blind, placebo-controlled studies randomising 3,073 moderate asthmatic adults to montelukast (n=1,439), beclomethasone (n=894) or placebo (n=740). The primary end point was asthma control days; other end points were forced expiratory volume in one second, beta-agonist use and nocturnal awakening. Analyses were conducted using BMI classification into normal (<25.0 kg.m-2; 52% of patients), overweight (25-29.9 kg.m-2; 32%) and obese (>or=30.0 kg.m-2; 16%) categories, as well as BMI as a continuous variable. The treatment groups were balanced for BMI, demographic characteristics and parameters of asthma control. The placebo response for all end points was generally lower with increasing BMI. Similarly, the response to the inhaled corticosteroid decreased, whereas the response to the leukotriene antagonist remained stable. In conclusion, post hoc data from the present study suggested that body mass index may influence the natural history of asthma control (as reflected by response to placebo) and may differentially influence response to the two active agents, warranting explicit testing in future prospective studies.