Effect of body mass index on self-reported exercise-triggered asthma

Exercise-induced asthma (EIA) is common in individuals diagnosed with asthma, with 80% to 90% experiencing asthma symptoms during moderate exercise. Asthma has been linked to obesity such that obesity may be a risk factor for adult-onset asthma. Adults with asthma disclose comorbid obesity as one of the most common barriers to exercise. Physical inactivity has been linked to increases in body mass index (BMI). Few studies have explicitly examined the relationship between BMI and reporting exercise as an asthma trigger. It was hypothesized that individuals with asthma who have an increased BMI will also have increased reports of exercise as an asthma trigger.

In total, 673 adult outpatients with asthma at Hôpital du Sacré-Cœur de Montréal in Montréal, Quebec, Canada underwent a brief sociodemographic and medical history interview. Patients provided information on their height, weight (used to calculate BMI), and triggers that generally provoked an asthma exacerbation (though it should be noted that a formal EIA test was not performed).

When individuals were classified as normal, overweight, or obese, logistic regression analysis revealed that those who were overweight had a 95% increase in the likelihood of reporting exercise-triggered asthma (odds ratio [OR], 1.95; 95% confidence interval [CI], 1.30-2.94) compared with those of normal weight, and this likelihood was more than doubled if the individuals were obese (OR, 2.34; 95% CI, 1.44-3.82). Assessing BMI as a continuous variable revealed that every 1-point increase in BMI was associated with a 9% increase in patients reporting exercise as a trigger (OR, 1.09; 95% CI, 1.04-1.14). All analyses were conducted adjusting for age, sex, asthma severity, and asthma control.

Results suggest that BMI influences the likelihood of reporting exercise as an asthma trigger, such that individuals with higher BMIs report exercise as an asthma trigger more often than those with a lower BMI. Given that the current study is cross-sectional, further prospective research is needed to define the causal pathway of this relationship.