Background: Current evidence regarding the relationship between childhood obesity, decreased response to inhaled corticosteroids (ICSs), and poor asthma control is conflicting.
Objectives: We assessed whether obesity (1) is associated with time to first exacerbation among children with asthma initiating step 3 maintenance therapies and (2) modifies the effectiveness of step 3 therapies.
Methods: A retrospective cohort study was conducted from clinical data linked to health and drug administrative databases. The cohort consisted of children aged 2 to 18 years with specialist-confirmed asthma who initiated medium/high-dose ICS monotherapy or low/medium-dose ICS with leukotriene receptor antagonist/long-acting β-agonist (combination therapy) at the Montreal Children's Hospital Asthma Center from 2000 to 2007. Children were classified as exposed to step 3 therapies when they were dispensed a corresponding drug claim during follow-up, whereas those without claims were classified as nonadherers. Marginal structural Cox models were used to estimate the effect of obesity (body mass index > 97th percentile) and treatment on time to exacerbation, which was defined as any emergency department visit, hospitalization, or use of oral corticosteroids for asthma.
Results: Of the 4621 cohort patients, 231 initiated ICS monotherapy, and 97 initiated combination therapy. The hazard ratio (HR) for obesity was 1.67 (95% CI, 1.41-1.98). Compared with nonobese nonadherers, the HR for obese nonadherers was 1.54 (95% CI, 0.97-2.45); the HR for ICS monotherapy in obese and nonobese children was 0.85 (95% CI, 0.47-1.52) and 0.58 (95% CI, 0.37-0.91), respectively; and the HR for combination therapy in obese and nonobese children was 0.50 (95% CI, 0.13-1.89) and 0.46 (95% CI, 0.23-0.92), respectively.
Conclusion: Obesity might be a determinant of shorter exacerbation-free time in children with asthma; however, we could not rule out a differential response to step 3 therapies by obesity status, potentially because of a lack of precision.
Keywords: Asthma; inhaled corticosteroid combination therapy; inhaled corticosteroid monotherapy; marginal structural Cox model; obesity.
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