Body mass index and phenotype in subjects with mild-to-moderate persistent asthma

Background: Although obesity has been hypothesized to worsen asthma, data from studies of subjects with well-characterized asthma are lacking. Objective: We sought to evaluate the relationship between body mass index (BMI), asthma impairment, and response to therapy. Methods: BMI (in kilograms per meter squared) and asthma phenotypic and treatment response data were extracted from Asthma Clinical Research Network studies. The cross-sectional relationship between BMI and asthma impairment was analyzed, as was the longitudinal relationship between BMI and response to asthma controller therapies. Results: One thousand two hundred sixty-five subjects with mild-to-moderate persistent asthma were evaluated. Analyses of lean versus overweight/obese asthmatic subjects demonstrated small differences in FEV(1) (3.05 vs 2.91 L, P = .001), FEV(1)/forced vital capacity ratio (mean, 83.5% vs 82.4%; P = .01), rescue albuterol use (1.1 vs 1.2 puffs per day, P = .03), and asthma-related quality of life (5.77 vs 5.59, P = .0004). Overweight/obese asthmatic subjects demonstrated a smaller improvement in exhaled nitric oxide levels with inhaled corticosteroid (ICS) treatment than did lean asthmatic subjects (3.6 vs 6.5 ppb, P = .04). With ICS/long-acting beta-agonist treatment, overweight/obese asthmatic subjects demonstrated smaller improvements in lung function than lean asthmatic subjects, with an 80 mL (P = .04) and 1.7% (P = .02) lesser improvement in FEV(1) and FEV(1)/forced vital capacity ratio, respectively. Significant differences in therapeutic response to leukotriene modifiers between BMI categories were not observed. Conclusions: Increased BMI is not associated with clinically significant worsening of impairment in subjects with mild-to-moderate persistent asthma. There is a modest association between increased BMI and reduced therapeutic effect of ICS-containing regimens in this patient population. Prospective studies evaluating the effect of being overweight or obese on treatment response in asthma are warranted. (J Allergy Clin Immunol 2009;123:1328-34.)