After analyzing results of a survey of more than 3,000 adults with asthma, researchers at Emory Crawford Long Hospital have found that obese patients with asthma are more likely to have severe asthma when compared to those who are not overweight.
The results of this study will be presented on Wednesday, May 23 at the American Thoracic Society 2007 International Conference in San Francisco.
"Approximately 65 percent of adults in the U.S. age 18 or older are either overweight or obese," says Brian Taylor, MD, a pulmonary fellow and researcher at Emory Crawford Long Hospital. "And similar to the obesity epidemic, there has also been a substantial increase in the prevalence of asthma.
"While there have been many studies on the association between obesity and asthma incidence, few have examined obesity and its relation to asthma severity," explains Dr. Taylor.
Fernando Holguin, MD, MPH, assistant professor of pulmonary medicine, Emory University School of Medicine, and physician at Emory Crawford Long Hospital and senior researcher on the study, says, "To our knowledge, this is one of the most comprehensive and largest all-asthma surveys showing the association between asthma severity and obesity using a broad range of severity outcomes. "However, we still cannot determine exactly how asthma severity and obesity are linked; it is possible that reduced physical activity caused by more severe asthma may lead to weight gain," says Dr. Holguin.
The researchers state there may be a connection with the hormone leptin, which is produced by fat cells and plays a role in body weight regulation. Previous research suggests leptin may also contribute to inflammation of airways seen in patients with asthma.
To further understand how obesity may impact the severity of asthma, the Emory researchers looked at the association of body mass index (BMI) to quantify a patient's body size with the following measures of severity: respiratory symptoms, healthcare utilization (emergency room visits or other unscheduled doctor visits for asthma), medication usage, missed days at work and the Global Initiative for Asthma (GINA) severity classification. GINA is an international society aimed at standardizing asthma care. Medication usage was evaluated for the 90-day period immediately preceding the survey.
The researchers examined data from the four-state sample of the National Asthma Survey, one of the largest diverse surveys of all asthma patients in the U.S. The survey, collected over a one-year period, consists of self-reported, physician-diagnosed patients with asthma.
The researchers also adjusted for certain variables including: gender, race, age, smoking status, education level, income, employment status, family history of asthma and residence in a metropolitan area to ensure these variables were not playing a role in the results. Even after adjusting for the variables, the researchers still found the same outcome.
"Our analysis showed that out of more than 3,000 patients with asthma, obese patients were 66 percent more likely to report continuous symptoms, 36 percent more likely to miss more days of work and 52 percent more likely to be classified as having either moderate or severe persistent asthma when compared to non-overweight people," says Dr. Taylor. "We also noted that obese patients were more likely to have less education, be unemployed and be African-American."
The researchers found no significant differences with regard to smoking status and family history of asthma.
Other outcomes also found to be more common in obese patients with asthma included more frequent emergency room visits as well as greater use of both daily controller and as-needed rescue medications. Further, obese patients were less likely to be in asthma remission compared to non-overweight patients.
As demonstrated in previous studies, the associations of asthma severity and obesity in this study seem to be slightly stronger in women than men.
The Emory Crawford Long Asthma Translational Research Center, led by Dr. Holguin, is currently studying how weight loss and hormones produced by fat cells affect the airways of both patients with asthma as well as healthy adults.