ATS: Asthma Severity Exacerbated by Excess Weight

SAN FRANCISCO, May 23 -- Obesity makes asthma not only more common but worse, researchers reported here.

Obese asthma patients were 66% more likely to report having constant symptoms, 47% less likely to be in remission, and 52% more likely to have severe persistent asthma than those who were not overweight, found Brian Taylor, M.D., of Emory University in Atlanta, and colleagues

The findings emerged from a survey that screened households for members with physician-diagnosed asthma, they reported at the American Thoracic Society meeting here. The four-state sample in the analysis included 3,059 self-referred adults.

John Mastronarde, M.D., of Ohio State University in Columbus, who chaired the session where the results were presented, commented that obesity has been associated with increased prevalence of asthma, but this is one of the first studies to correlate obesity with severity.

"That obviously can be important for clinicians and those of us who take care of asthma patients in that you may tailor your treatment a little bit different now depending on the patient's body mass index," he said.

"You may anticipate that patients who are obese will need more aggressive therapy or different therapy to control their asthma," he added in commenting on the study at a press conference.

Previous studies had been limited by small size, inconsistent definitions of asthma severity, and limited adjustment for confounding factors. So Dr. Taylor and colleagues used a detailed set of data for four states-Alabama, Texas, California, and Illinois--from the larger National Asthma Survey.

All had current asthma, defined as symptoms, medications, or physician visits for asthma in the prior three to five years. About a third of the participants fell into normal weight, overweight and obese categories, respectively.

After adjustment for race and ethnicity, education, income, and employment status in a multivariate analysis, the findings for obese versus normal weight respondents were:

• Less likely to be in remission according to Global Initiative for Asthma (GINA) criteria (OR 0.53, 95% CI 0.36 to 0.79).
• More likely to have persistent, GINA Class II to IV, asthma (OR 1.35, 95% CI 1.03 to 1.77).
• More likely to have severe persistent, GINA class IV, asthma (OR 1.52, 95% CI 1.06 to 2.17).
• Greater likelihood of reporting symptoms "all the time" in the prior 30 days (odds ratio 1.66, 95% confidence interval 1.09 to 2.54).
• More likely to have at least one emergency department in the prior year (OR 1.46, 95% CI 1.00 to 2.14).
• More likely to have missed more than two days of work in the prior year (OR 1.36, 95% CI 1.01 to 1.83).
• More likely to use inhaled corticosteroids (OR 1.35, 95% CI 1.01 to 1.80).
• More likely to have used short-acting beta₂ agonists (OR 1.36, 95% CI 1.6 to 1.76).

When overweight respondents who were not obese were compared with those at normal weight, the findings for each asthma outcome still tended to be worse,, but the only significant difference was remission (OR 0.52, 95% CI 0.35 to 0.77).

The study was limited by lack of spirometry data and reliance on participants to accurately report physician diagnosis of asthma as well as height and weight, on which body mass index was calculated.

Furthermore, the cross-sectional design precluded the researchers from determining causality.

Dr. Taylor postulated that the mechanism by which asthma and obesity are linked might be that the hormone leptin plays a role in both body weight regulation and inflammation of airways.

Whatever the mechanism turns out to be, the link opens up different potential therapeutic targets for obese patients, Dr. Mastronarde said.

"For example if your patient is very obese with severe asthma, you might really start looking aggressively at weight loss reduction to not only treat their obesity but also their asthma," he said.

Dr. Taylor and colleagues said they are now studying whether bariatic surgery improves airway function compared with obese patients who do not undergo the surgery.