Researchers from National Jewish Health found that overweight or obese patients with mild and moderate forms of asthma may have a reduced response to their medications.
"With both asthma and obesity on the rise in recent years, there has been much interest in the possible link between these two conditions," said lead author E. Rand Sutherland, MD, MPH, associate professor of medicine at National Jewish Health. "By studying a well characterized group of patients with asthma, we were able to determine that increased weight is not associated with more severe asthma. Although benefits can be obtained with weight loss in other diseases, these findings suggest that an improvement in asthma may not necessarily result from weight loss.”
"The findings also suggest that patients and physicians should be aware that obese asthma patients may not respond well to corticosteroids, the most successful controller medication for asthma, which can affect dosing decisions and choices of possible alternatives to steroids," said Sutherland in an announcement from National Jewish Health.
According to National Jewish Health, previous studies suggested that obesity predisposes people to developing asthma, suffering more severe asthma symptoms, and responding less to medications. However, the studies generally relied upon patients’ reports of their diagnosis and symptoms rather than using more precise tools to characterize patients.
To conduct their study, Sutherland and colleagues examined the issue in a well-characterized group of 1,256 patients who had participated in NIH-sponsored studies. The participants were divided into groups by body mass index (BMI). Participants were divided into a group characterized by a BMI of less than 25 or greater than or equal to 25.
Lean asthma patients had only slightly greater forced expiratory volume in one second, or FEV1 (3.05 liters vs 2.91 liters), and slightly greater ratio of FEV1 to forced vital capacity (83.5% vs. 82.4%). Slightly greater use of rescue inhalers was also found among overweight patients (1.2 puffs per day vs. 1.1 puffs per day).
Among a subgroup of 183 people, lean patients taking inhaled corticosteroids alone showed a 55% greater reduction in exhaled nitric oxide. Lean patients taking a combination inhaled steroid and long-acting beta agonist increased their FEV1 by 80 more milliliters. There were no differences, however, between these patients in the number of asthma exacerbations.
"The data suggest overweight and obese people respond less well to controller medications for asthma than do their lean counterparts," said Sutherland. "These data come from already-completed studies designed to answer other questions, however, and ongoing studies are being conducted to more definitively determine the effect of increased weight on treatment response in asthma."
The findings appear in the June 2009 issue of the Journal of Allergy and Clinical Immunology.