Influence of distinct asthma phenotypes on lung function following weight loss in the obese. Issue 8 (19th August 2014)

• Record Type: Journal Article
• Authors: Chapman, David G.; Irvin, Charles G.; Kaminsky, David A.; Forgione, Patrick M.; Bates, Jason H.T.; Dixon, Anne E.
• Is Part Of: Respirology. Volume 19:Issue 8(2014)
• Page Start: 1170
• Page End: 1177
• Publication Date: 2014-08-19
• Subjects: Respiratory organs -- Diseases -- Periodicals; Respiratory organs -- Periodicals; 612.2
• DOI: 10.1111/resp.12368
• Languages: English
• ISSNs: 1323-7799

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <sec id="resp12368-sec-0001" sec-type="section"> <title>Background and objective</title> <p>There appears to be two distinct clinical phenotypes of obese patients with asthma—those with early‐onset asthma and high serum IgE (T<sub>H</sub>2‐high), and those with late‐onset asthma and low serum IgE (T<sub>H</sub>2‐low). The aim of the present study was to determine in the two phenotypes of obese asthma the effect of weight loss on small airway function.</p> </sec> <sec id="resp12368-sec-0002" sec-type="section"> <title>Methods</title> <p>T<sub>H</sub>2‐low (<italic>n</italic> = 8) and T<sub>H</sub>2‐high (<italic>n</italic> = 5) obese asthmatics underwent methacholine challenge before and 12 months following bariatric surgery. Dose–response slopes as measures of sensitivity to airway closure and narrowing were measured as maximum % fall forced vital capacity (FVC) and forced expiratory volume in 1 s/FVC, respectively, divided by dose. Resting airway mechanics were measured by forced oscillation technique.</p> </sec> <sec id="resp12368-sec-0003" sec-type="section"> <title>Results</title> <p>Weight loss reduced sensitivity to airway closure in T<sub>H</sub>2‐low but not T<sub>H</sub>2‐high obese asthmatics (pre‐post mean change ± 95% confidence interval: 1.8 ± 0.8 doubling doses vs −0.3 ± 1.7 doubling doses, <italic>P</italic> = 0.04). However, there was no effect of weight loss on the sensitivity to airway narrowing in either group (<italic>P</italic> = 0.8, T<sub>H</sub>2‐low: 0.8 ± 1.0 doubling doses, T<sub>H</sub>2‐high: −1.1 ± 2.5 doubling doses). In contrast, respiratory resistance (20 Hz) improved in T<sub>H</sub>2‐high but not in T<sub>H</sub>2‐low obese asthmatics (pre‐post change median interquartile range: 1.5 (1.3–2.8) cmH<sub>2</sub>O/L/s vs 0.6 (−1.8–0.8) cmH<sub>2</sub>O/L/s, <italic>P</italic> = 0.03).</p> </sec> <sec id="resp12368-sec-0004" sec-type="section"> <title>Conclusions</title> <p>T<sub>H</sub>2‐low obese asthmatics appear to be characterized by increased small airway responsiveness and abnormalities in resting airway function that may persist following weight loss. However, this was not the case for T<sub>H</sub>2‐high obese asthmatics, highlighting the complex interplay between IgE status and asthma pathophysiology in obesity.</p> </sec> </abstract>