Effect of increased body mass index on asthma risk, impairment and response to asthma controller therapy in African Americans

Objective: To explore whether obesity alters the risk, impairment and response to treatment in African Americans with asthma. Methods: The data used for this secondary analysis are from a 1-year study in African American subjects comparing fluticasone propionate/salmeterol 100/50 mu g combination (FSC) and fluticasone propionate 100 mu g (FP). Subjects were retrospectively stratified by body mass index (BMI) <20 [underweight], 20-24.9 [normal weight], 25-29.9 [overweight], 30-34.9 [obese I], 35-39.9 [obese II], and >= 40 [obese III] kg/m(2). Outcomes studied included impairment domains: FEV1, morning and evening peak expiratory flow (AM and PM PEF), daily albuterol use, daily symptom scores and future risk domain: exacerbations. Clinical trial registration: www.clinicaltrials.gov; NCT00102765 Results: There were 475 subjects evenly distributed between FSC and FP by baseline parameters. There were 207 subjects with a BMI >= 30, including 70 subjects with a BMI >= 40. Baseline BMI >= 40 was associated with numerically lower baseline AM and PM PEF. There was an attenuation of response to both treatments for only PM PEF (p < 0.05). By contrast, subjects with lower degrees of obesity or overweight did not differ from those with normal weight. The total population exacerbation rate was 2-fold greater in obese III subjects (39%) compared with subjects in other BMI categories (16-21%) (p < 0.05). A potential study limitation is the retrospective analysis of existing data. Discussion: Response to treatment was attenuated for PM PEF for subjects with BMI >= 40 and was also associated with an increased rate of asthma exacerbations.