Exercise Induced Asthma and Obesity

Abstract: Introduction 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. Methods 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). Results 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. Conclusion 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.

From press release:

Which Comes First: Exercise-Induced Asthma or Obesity?
ScienceDaily (Dec. 26, 2010) — Obese people are more likely to report exercise as a trigger for asthma. Of 673 people evaluated in a new study whose results are published in the journal The Physician and Sportsmedicine, 71 percent of participants reported exercise-induced asthma (ETA).

The findings are important, since 2.3 million Canadians are affected by asthma according to Statistics Canada.

ETA affects up to 90 percent of asthma sufferers, says lead author Simon Bacon, a professor at the Concordia Department of Exercise Science and a researcher at the Hôpital du Sacré-Coeur de Montréal. "Compared with normal-weight participants, patients who were overweight or obese were more likely to report ETA. To our knowledge, there are no studies that have explored this relationship," he says. "We also found that for every one-point increase in body mass index score was associated with a 9 percent increase in the probability of reporting exercise-induced asthma."

Participants who took part in the investigation suffered from intermittent as well as mild, moderate and severe persistent asthma. Their body mass index was calculated according to their reported height and weight. Patients were also asked to indicate factors -- exercise, animals, dust, pollen, aspirin, stress, emotions or cold air -- that could trigger their asthma.

"Exercise-induced asthma may lead to a sedentary lifestyle, increased weight and can fuel a downward spiral to worsened health," says Dr. Bacon. "Given the importance of exercise and regular physical activity in weight management, greater care should be taken when working with asthma patients to refer them to appropriate weight management specialists to help them control and safely reduce their weight."