(From the March 2015 Issue of PediatricsOnline)
While a connection between childhood obesity and asthma is well established, there have been few studies to define the biological factors that link the two conditions. The lack of information has left physicians with little guidance about how the asthma symptoms of overweight patients and their response to treatment may differ from those of lean children. Now, a study and its accompanying commentary published in the Journal of Allergy and Clinical Immunology are offering insight into how a child’s body weight may deeply impact the way that asthma is experienced — and ultimately managed.
Of the 56 asthmatic study participants, aged 10 to 17 years old, obese children (>85th percentile body mass index) were three times more likely to use bronchodilator rescue therapy at least once a week than lean children (20th percentile to 65th percentile BMI), despite the fact that both had similar rates of health care use and adherence to maintenance therapy. Study authors also found that obese children were more likely to report shortness of breath as the primary symptom of unmanaged disease versus lean children, who were more likely to report coughing.
“We have several plausible theories for why asthma and obesity seem to go hand in hand, ranging from genetics to inflammation to mechanical airway obstruction, but very little information about how any of those factors might impact the way overweight children present clinically,” said David Stukus, MD, an allergy and immunology expert at Nationwide Children’s Hospital who wrote the study’s accompanying editorial. “With childhood asthma and obesity at epidemic levels, this study offers a much needed look at the distinct differences in asthma symptoms in obese versus lean kids, and gives us a starting point for offering our patients individualized care.”
Similar Lung Function, but Different Perception of Asthma Control
Dr. Stukus points out that despite previous studies suggesting that overall lung function is more impaired in overweight and obese asthma patients, the recent study did not find any such differences. Interestingly, overweight and obese children in this study were less reactive to a methacholine challenge, which constricts airways; they required roughly four times the dose of methacholine before reaching a significant response.
Also in contrast to earlier research, the study found no differences in reported wheezing, the symptom most commonly associated with overweight and obese children. Furthermore, obese patients reported more symptoms of gastroesophageal reflux disease (GERD) than lean children.
In their discussion, the study authors say that the disparity in rescue inhaler use and prevalence of GERD, coupled with the finding that obese and lean children have similar lung function, suggests that obese kids may be mistaking symptoms unrelated to asthma for a worsening of their condition. They hypothesize that GERD and physical chest restriction stemming from obesity may not exacerbate asthma at all, but may, by causing shortness of breath, prompt obese kids to increase use of rescue inhalers and subjectively report poor control of the disease.
However, the authors also note that the study was not designed to determine if GERD symptoms are causing obese children to experience dyspnea, so more research is needed to validate the potential connection.
Dr. Stukus says that the intriguing findings support the use of lung function testing along with the current guidelines suggested by The National Heart, Lung, and Blood Institute, which recommend a thorough assessment of medication adherence, comorbid conditions and environmental exposures before increasing therapy in patients with poorly controlled asthma.
“Some children might even be able to step down their level of controller medication, particularly if symptoms are deemed to be due to other causes that can be better addressed through non-asthma-related interventions,” said Dr. Stukus. “The findings underscore the fact that we cannot use a ‘one-size-fits-all’ approach with our asthma patients.”
Stukus DR. Obesity and asthma: The chicken or the egg? The Journal of Allergy and Clinical Immunology. 2014 Dec 18. Pii: S0091-6749(14)01594-2. [Epub ahead of print]
Lang JE, Hossain MJ, Lima J. Overweight children report qualitatively distinct asthma symptoms: Analysis of validated symptom measures. The Journal of Allergy and Clinical Immunology. 2014 Oct 14. Pii: S0091-6749(14)01204-4. [Epub ahead of print]