Body mass index and asthma severity among adults presenting to the emergency department

Study objectives: Among adults presenting to the emergency department (ED) with acute asthma, we sought to determine the prevalence of obesity, and the relation of body mass index (BMI) to asthma severity in this high-risk population. Design: Multicenter, prospective cohort study. Setting: Twenty-six North American EDs. Participants: Five hundred seventy-two patients aged IS to 54 years presenting with acute asthma. Interventions: None. Measurements and results: A standardized interview assessed demographic characteristics, asthma history, and details of the current asthma exacerbation. Data on ED medical management and disposition were obtained by chart review. Three of four asthmatic patients were either overweight (BMI, 25 to 29.9; 30%) or obese (BMI, greater than or equal to 30; 44%). Normal weight/underweight, overweight, and obese patients did not differ on several markers of chronic asthma severity; obese subjects tended to rate symptoms more severely and to use more inhaled beta-agonists in the 6 h hours prior to ED presentation despite a significantly higher initial percentage of predicted peak expiratory flow (PEF) [44%, 45%, and 51%, respectively; p < 0.05]. The three BMI groups responded similarly to acute therapy in the ED, with all groups demonstrating reversible airway obstruction. The sex distribution by BMI group differed markedly (p < 0.001), with women less often overweight (40% vs 24%) and more often obese (30% vs 52%). Since women were more likely have a higher initial PEF (45% vs 53%, p < 0.001), we stratified by sex to further examine the relation of BMI to asthma severity. The observed BMI-asthma associations were due largely, but not entirely, to confounding by sex. Conclusions: Despite lingering concerns about the veracity of "asthma" among obese individuals, asthma exacerbations among obese and nonobese adults were remarkably similar. Potential differences (eg, in symptom perception, use of inhaled beta-agonists before ED presentation, initial PEF rate) were due, in large part, to confounding by sex.