A new study has found that obese patients with asthma are more likely to have severe asthma when compared to those who are not overweight.
The study was conducted by a team of researchers including Brian Taylor, Fernando Holguin and colleagues at Emory University.
As part of the study, researchers conducted a survey of more than 3,000 adults by examining a 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.
To further understand how obesity may impact the severity of asthma, 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.
"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," Taylor said.
"We also noted that obese patients were more likely to have less education, be unemployed and be African-American," he added.
Researchers also found that frequent emergency room visits and greater use of both daily controller and as-needed rescue medications was more common in obese patients with asthma. 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.
"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," Holguin said.
"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," Holguin added.
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 that leptin may also contribute to inflammation of airways seen in patients with asthma.
The findings of the study were presented at the American Thoracic Society 2007 International Conference in San Francisco.