Obese-asthma phenotype linked to increased asthma severity

Naveed Saleh, MD, MS, for MDLinx | May 17, 2018

During the past two decades, the synchronous rise of asthma and obesity prevalence has suggested an association between the two conditions. Two new studies published in the Journal of Allergy and Clinical Immunology further examined the obesity-asthma phenotype.

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Two new studies look at the association between obesity and asthma severity.

In one study, Cristina Longo, MSc, McGill University, Montreal, Quebec, Canada, and colleagues performed a retrospective cohort study that included patients between the ages of 2 and 18 years with specialist-confirmed asthma who initiated step 3 maintenance therapies at the Montreal Children’s Hospital Asthma Center between 2000 and 2007.

Step 3 maintenance therapies involve either medium/high-dose inhaled corticosteroids (ICS) monotherapy or low/medium-dose ICS with a long-acting β-agonist/leukotriene receptor antagonist (ie, combination therapy).

The researchers identified 231 children who used ICS monotherapy and 97 who used combination therapy.

The composite endpoint for this study was asthma exacerbation defined as whichever of the following occurred first:

  • Short course of oral corticosteroids
  • Acute care visit
  • Hospital admission related to an asthma exacerbation

The researchers found that obese children with asthma experienced an increased risk of exacerbation when compared with non-obese children after commencing ICS monotherapy or combination therapy. Furthermore, ICS monotherapy may be less effective in obese children, whereas combination therapy is equally effective in obese and non-obese children.

However, the researchers could not rule out a differential response to step 3 maintenance therapies among patients as a potential reason for shorter exacerbation-free periods in obese children with asthma due to a potential lack of precision. The authors stated that the exclusion of children covered by private drug insurance plans in the study affected the ability to rule out a potential differential treatment response by obesity status.

The researchers highlight the clinical implications of their study: “Obese children with asthma appear to be more susceptible to early exacerbations after initiation of step 3 maintenance therapies; a different management approach may be warranted for obese children, pending improved weight status.”

In another study, Jason E. Lang, MD, MPH, Duke University School of Medicine, Durham, NC, and colleagues examined the links among obesity, asthma severity, and ICS response in preschool-aged children.

In this post hoc study, researchers analyzed data from three large prospective studies of preschool children enrolled in the Childhood Asthma Research and Education (CARE) and AsthmaNet networks.

“We evaluated the effects of early life OW [overweight/obesity] status on prospectively determined asthma symptom days (AD) and exacerbations in children treated with either ICS (daily or intermittent step up) or placebo,” wrote the researchers.

They hypothesized that OW status would lead to greater AD and exacerbations among both placebo-treated and ICS-treated children.

Data from 736 preschool children aged between 24 and 59 months with recurrent wheezing or mild persistent asthma were examined. The children were randomized to one of three multicenter trials in which researchers administered daily ICS, intermittent ICS, or placebo.

“The primary analyses were comparisons between NW [normal weight] and OW in AD and exacerbations,” wrote the researchers.

Results showed that in the placebo group, overweight children experienced more asthma days and exacerbations than did normal weight children. However, in the experimental groups, overweight children experienced a marked clinical response to ICS, unlike that experienced by older OW children and adults.

One limitation of this study was its post hoc design, which is typically used to generate hypotheses. Therefore, the results should be taken with caution until the findings can be reproduced.

“In conclusion,” wrote the researchers, “early life high BMI does appear to worsen both impairment and risk domains of asthma severity in preschool children off controller therapy. Interventions that reduce early life weight gain and OW status may benefit respiratory health in preschool children.”

Taken together, these results indicate increased disease severity in children with the obesity-asthma phenotype, as well as differential responses to asthma therapy.

To read more about these studies, click here and here.

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