Obese adults with asthma are more likely than their leaner counterparts to have severe, persistent disease, according to a new large study. The study was carried out by Dr. Brian Taylor of Emory Crawford Long Hospital, Atlanta.
Obese patients, compared with normal-weight adults, were 47 percent less likely to have their asthma in remission and were 52 percent more likely to have severe persistent asthma, Taylor said.
The increase in childhood asthma may be explained by the rise in obesity, a US study has suggested. They suggest increased weight might lead to inflammation in the respiratory tract, which could be the key factor in inducing asthma. The way weight affects the lungs could also affect the airways, leading to a child developing asthma symptoms. The study, by researchers from University Children’s Hospital, Munich, Germany and Harvard Medical School, USA, is published in the journal Thorax.
According to a recent review by Stephanie A. Shore, PhD, and Jeffrey J. Fredberg, PhD, both from the Harvard School of Public Health in Boston, increased abdominal and chest wall mass in obese people causes lower functional residual capacity. And since lung volume is a major determinant of airway diameter, it is possible that these changes in residual capacity allow smooth airway muscles to shorten excessively when activated.
Another possibility is that obese persons breathe at higher frequencies–but substantially smaller tidal volumes–compared with nonobese individuals. As a result, the bronchodilatory effect of tidal strains is compromised and the obese person is predisposed toward increased airway responsiveness.
Although the reason why obesity increases asthma severity is not entirely clear, evidence suggests that the hormone leptin, which is produced by fat cells and plays a role in weight regulation and asthma-related airway inflammation, may be involved.
