Grant: Travel Awards - Institute Community Support

Context: Obesity is an established risk factor for asthma and is also associated with poorer asthma control. Obese patients with asthma may be less responsive to inhaled corticosteroids (ICSs) and long-acting beta-2 agonists (LABA). It is postulated that the mechanical stress placed on the thoracic cage by excess fat leads to decreased lung deposition of ICSs and that genetic polymorphisms may lead to decreased response to LABAs. Recent research suggests that oral anti-leukotrienes (LTRAs) may be more effective in obese patients, since their absorption is not dependent on lung mechanics. Objective: To determine if the relative effectiveness of ICS/LTRA when compared to ICS/LABA combination therapy (using similar ICS doses) in achieving asthma control is modified by excess weight among children and adolescents with uncontrolled mild to moderate persistent asthma. Design: A retrospective cohort design using a marginal structural cox proportional hazards model to estimate treatment effects. Setting: The Montreal Children's Hospital Asthma Center. Participants: Children aged 6-17 years with confirmed asthma referred to or followed by the Asthma Center between January 1st 2000 and December 2006. Main outcome: Asthma control defined as any evidence of acute health care visits, hospital admissions, or use of oral corticosteroids during the 1-year follow-up period. Expected Results: Of the 1053 patients in our asthma cohort, 222 (21.1%) are obese. We expect that the relative effectiveness of ICS/LTRAs compared to same-dose ICS/LABA will be modified by excess weight, after applying inverse-probability treatment and censoring weights. Conclusions: Obese pediatric patients may require alternative asthma maintenance strategies. Further research is warranted to understand why obese patients respond differently to asthma controller therapy than their normal weight counterparts.