Does Obesity Increase Respiratory Tract Infections in Patients with Asthma?

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.

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.

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.

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.

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.