A new study presented at the American Thoracic Society 2007 International Conference finds that obese people are significantly more likely to have persistent or severe persistent asthma than their thinner counterparts.

The study presented on May 23 looked at 3,059 adults with asthma, who were divided into three groups: non-overweight, overweight and obese, based on their body mass index (BMI). Compared with non-overweight asthma patients, obese patients (BMI=30) were more likely to report having continuous symptoms, have more ER visits, miss more days of work, use more rescue inhaler medications and use inhaled steroids to control asthma.

Obese patients were 66% more likely to report having asthma symptoms all of the time, were 47% less likely to be in asthma remission, and 52% more likely to have severe persistent asthma than non-overweight people with asthma. Obese asthmatics were also 36% more likely to miss more than two days of work per year due to asthma than non-overweight asthma patients.

"There have been a number of studies on obesity and asthma prevalence, but until now there has been little data on obesity and asthma severity," says lead researcher Brian Taylor, M.D., of Emory Crawford Long Hospital in Atlanta.

The studies that have been done have been small, but this study took data from the National Asthma Survey, which includes 5,741 asthmatics, Dr. Taylor notes. "We had enough data to adjust for other factors, such as gender, race, income and employment status, and ensure that these factors were not playing a role in the results. Even after taking these variables into account, the association between obesity and asthma severity still held."

Dr. Taylor notes that this study, like many previous studies, shows the link between asthma and obesity is more prominent in women. "A big part of that is simply that 70% of the study subjects were women," he says. "We did find a statistically significant association between obesity and asthma severity in men, too."

While it's not known for sure how asthma and obesity are linked, Dr. Taylor notes that one potential mechanism seems to be an association between the hormone leptin, which is produced by fat cells and plays a role in body weight regulation, and inflammation of airways seen in asthma. Obesity also may impact the lungs in other ways to increase the risk of asthma.

A recent review of studies, which was published in the ATS's own American Journal of Respiratory and Critical Care Medicine, suggested that asthma incidence could be reduced by interventions targeting overweight and obesity. Led by Dr. Fernando Holguin, Dr. Taylor and colleagues are now studying whether patients who undergo bariatic, or weight-loss, surgery experience an improvement in airway function compared with obese patients who don't have the surgery.

"Body Mass Index as a Predictor of Asthma Severity in Adults with Asthma. Results from the 4-State National Asthma Survey." (Session D94; Abstract # 68)