Does Obesity Increase Respiratory Tract Infections in Patients with Asthma?

Background: Because respiratory tract infections (RTIs) precede most exacerbations, a better understanding of the risk factors of RTIs and RTI-associated exacerbations in patients with asthma is a pressing public health need. Obesity in patients with asthma is associated with worse asthma control and higher asthma-associated health care utilization, but its effect on RTI risk is unknown. Objective: We aimed to study the association of body mass index (BMI) classification on the risk of self-reported RTIs and related asthma morbidity among adults and children with asthma. Methods: This post hoc analysis of 5 large asthma trials involving 747 children and 1287 adults compared BMI classification, defined as lean, overweight, and obese based on age-appropriate BMI and BMI-percentile conventions. The primary outcome was rate of visits with RTIs. Secondary asthma outcomes included upper respiratory infection (URI) severity, systemic steroid use, and health care contact. Results: Children had 1.4 times the rate of RTI compared with adults (95% confidence interval 1.27-1.56). In all participants, BMI classification did not affect the rate of visits with RTI. In children, BMI classification did not affect URI severity, all-cause asthma events, or RTI-associated asthma events. However, in adults, higher BMI classification was associated with an increase in moderate/severe URI (P =.02). Adults with higher BMI classification also had increased rates of all-cause and RTI-associated asthma exacerbations requiring systemic steroids and health care contact. Conclusions: BMI classification was not associated with an increased risk of RTIs in children or adults. In adults only, obesity was associated with increased URI severity and all-cause and RTI-associated asthma morbidity.