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Friday, April 10, 2015

Overweight children report qualitatively distinct asthma symptoms: Analysis of validated symptom measures

The relationship between overweight/obesity and asthma phenotype in children remains inadequately defined. Several large epidemiologic studies have demonstrated that obesity increases the risk of physician-diagnosed asthma and is associated with greater asthma-related health utilization and asthma that is more problematic and difficult to control. This discrepancy regarding the impact of obesity suggests that more in-depth and novel assessments of lean and obese asthmatic children may be required. Specifically, few studies have addressed how obese patients perceive and report asthma symptoms. This led Lang et al to determine the qualitative differences in symptoms between lean and overweight/obese children with early-onset, atopic asthma (J Allergy Clin Immunol 2015; 135(4): 886-893).

The authors conducted a cross-sectional analytic study of lean and overweight/obese 10-17 year old children with persistent, early-onset asthma. Participants provided a complete history, qualitative and quantitative asthma symptom characterization, and lung function testing. They determined associations between weight status and symptoms using multivariable linear and logistic regression methods. The authors report that overweight/obese and lean children displayed similar baseline spirometry values. However, despite lower fraction of exhaled nitric oxide and reduced methacholine responsiveness, overweight/obese children reported requiring rescue treatments more than 3x that of lean children. Weight status affected the child’s primary symptom reported with loss of asthma control; overweight/obese children more often reported shortness of breath and less often reported cough.   Using three validated questionnaires for assessing asthma symptom control, the authors showed that overweight/obese status was consistently associated with greater symptom reporting.  Subscale analysis suggested that shortness of breath and self-medication with rescue medication consistently drove the worse asthma scoring.  Gastroesophageal reflux (GER) scores were higher in overweight/obese children and appear to mediate overweight/obesity-related asthma symptoms.

Lang concludes that overweight/obese children with early-onset asthma display poorer asthma control and a distinct pattern of symptoms. Moreover, greater shortness of breath and β-agonist use appears to be partially mediated via esophageal reflux symptoms, which may lead to overweight children with asthma falsely attributing exertional dyspnea and esophageal reflux to asthma and excess rescue medication use. Because dyspnea from asthma is a major driver of anxiety, reduced quality of life, health care utilization, and medication use, a greater understanding of the distinct sensory mechanisms of dyspnea is needed. Until systematic weight loss interventions become more feasible, respiratory physicians may serve their patients better by considering and discussing alternative causes of dyspnea in self-management plans.

Question for the authors:
Are there other factors associated with obesity that may be a factor in the severity of asthma symptoms, such as socioeconomic and health related factors?

Several comorbidities associated with obesity are also likely to influence asthma either directly or by complicating its perception and management.  The best examples include snoring/sleep apnea, immune and metabolic derangements and impaired cardiopulmonary reserve.  We adjusted for presence of snoring in our analysis which did not affect our results (as did adjusting for GER scores).  Lower socioeconomic status has been associated in the past with greater prevalence of obesity and worse asthma control, thereby making it a possible confounding factor.  However, several socioeconomic and environmental factors were measured in our study including race, ethnicity, parental education, income, inutero smoking and later environmental smoke exposure.  None of these measures were associated with overweight/obesity status in our study.  We did not measure for levels of activity.  The effect of daily activity on disease activity, response to controller therapy, and perception of asthma symptoms requires more investigation and may provide important insights into the relationship between obesity and asthma.  

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