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The Asthma-Obesity Connection
Could Link Explain Why Some Kids Don't Outgrow Asthma as Previously Believed?
By Sid Kirchheimer
WebMD Medical News Reviewed By Brunilda Nazario, MD
on Tuesday, July 13, 2004
July 13, 2004 -- Despite popular belief that many kids outgrow asthma, new research shows that the condition usually persists into adolescence -- and childhood obesity may play a major role in explaining why.
"Complete remission of asthma in adolescents and adults does occur, but it's a lot less common than what has been believed," says Stefano Guerra, MD, PhD, MPH, of the University of Arizona College of Medicine in Tucson. "We used to think that the majority of children outgrew asthma around the time of puberty. But our study shows that the majority continue to display symptoms after they reach puberty."
It has long been thought that around age 12, around the time of puberty, many children outgrow asthma. But after tracking nearly 800 children and examining them at ages 6, 8, 11, 13 and 16, Guerra's team at the Arizona Respiratory Clinic finds that 60% of children with asthma continued to display symptoms well into their teenage years.
And kids who were overweight or obese at the time of puberty were three times more likely to continue to have asthma problems into their teen years, according to their study, published in this month's American Journal of Respiratory and Critical Care Medicine.
Threefold Risk in Adults, Too
"Obesity definitely plays a role in the persistence of asthma, but the million-dollar question is, specifically how?" Guerra tells WebMD. "One common argument is that obese children are less likely to exercise, which may have some effect on the condition. But there is evidence, not only from our study but also others, that obesity precedes asthma. It seems to be a cause of asthma, rather than an effect."
Actually, the asthma-obesity connection has been a hot topic of research since 1998, when Harvard Medical School researchers first noted a possible connection, discovering that obese adults were three times more likely to develop asthma than slimmer folks. That research, later published in Archives of Internal Medicine, tracked the weight, height, and asthma rates of some 90,000 nurses -- but not children -- and essentially found, "the heavier you are, the more likely you are to get asthma," according to researcher Carlos Camargo, MD.
While that study didn't determine how obesity increases asthma risk, Camargo said at the time that excess weight compresses the airways, making them smaller and therefore more reactive to cold and other asthma triggers. Since then, various studies have been done on children. In one, German researchers noted that the heaviest children were 77% more likely to have asthma symptoms than kids of normal weight, but no similar relationship was noted between obesity and allergies.
Common Gene Discovered
More recently, the discovery of a new gene may explain the link. At last year's annual meeting of American Academy of Allergy, Asthma & Immunology (AAAAI), researchers noted that the gene, which belongs to a family of similar proteins found to cause insulin resistance (a common preface to obesity) and obesity in mice, also occurs in the lungs of mice with asthma, suggesting a possible link of the two conditions. One of those researchers, Marc E. Rothenberg, MD, PhD, tells WebMD that his gene discovery is just the latest piece linking the two conditions.
"There appears to be common mechanisms between both obesity and asthma, and my prediction is that we will see the two conditions have common genetic factors, common molecules and common causes that explain the association," says Rothenberg, director of Allergy and Clinical Immunology and a professor of pediatrics at Cincinnati's Children's. He is currently doing a new study on the asthma-obesity link.
"Already, we know that inflammation is involved in both asthma and obesity, as well as other diseases," he tells WebMD. "I think what will probably eventually happen is that drugs developed to block elements of obesity will also improve asthma as well. We know that as obese people lose weight, their asthma tends to improve."
The Asthma-Obesity Connection
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