Airway inflammation in obese and nonobese patients with difficult-to-treat asthma

• Published in: Allergy (Copenhagen) Vol. 63; no. 5; pp. 570 - 574
• Main Authors: van Veen, I.H, ten Brinke, A, Sterk, P.J, Rabe, K.F, Bel, E.H
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-05-2008; Blackwell Publishing Ltd
• Subjects: Adolescent; Adult; Aged; Asthma; Asthma - drug therapy; Asthma - etiology; Asthma - physiopathology; Body Mass Index; Disease management; Eosinophils; Female; Gastroesophageal Reflux; Humans; inflammation; Inflammation - etiology; Inflammation - immunology; Inflammatory diseases; Lung - immunology; Lung - physiopathology; Male; Middle Aged; Nitric Oxide - metabolism; Obesity; Obesity - complications; Respiratory Function Tests; risk factor; Risk Factors; Severity of Illness Index; Sleep Apnea Syndromes; Sputum - immunology
• ISSN: 0105-4538; 1398-9995
• DOI: 10.1111/j.1398-9995.2007.01597.x

Asthma and obesity are associated disorders, but the contribution of obesity to difficult-to-treat asthma as well as the mechanisms responsible for this relationship are unclear. The aim of this study was to investigate the relationship between obesity (body mass index >= 30) and factors related with asthma severity in patients with difficult-to-treat asthma. One hundred and thirty-six nonsmoking asthmatic adults with persistent symptoms despite high doses of inhaled or oral corticosteroids and long-acting bronchodilators were studied [70% female, median (range) age 44.6 (18-75) years, 32% on daily oral corticosteroids]. The association between obesity, lung function parameters [forced expiratory volume in 1 s (FEV₁), functional residual capacity/total lung capacity (FRC/TLC)], inflammatory markers [blood eosinophils, sputum eosinophils and neutrophils, exhaled nitric oxide (FENO), airway hyperresponsiveness, C-reactive protein (CRP)] and aggravating co-morbid factors (severe chronic sinus disease, gastro-esophageal reflux, recurrent respiratory infections, psychopathology and obstructive sleep apnea) was investigated. Obese patients (n = 29) had a higher FEV₁%pred (P = 0.05) and a lower FRC/TLC%pred (P < 0.01) compared with nonobese patients (n = 107). Body mass index was inversely related with sputum eosinophils (r = -0.36, P < 0.01) and FENO (r = -0.30, P < 0.01). Obese patients had an increased risk for gastro-esophageal reflux (OR = 2.3) and sleep apnea (OR = 3.1). Obesity in patients with difficult-to-treat asthma is inversely related with sputum eosinophils and FENO, and positively associated with the presence of co-morbid factors and reduced lung volumes. This suggests that other factors than airway inflammation alone explain the relationship between obesity and asthma severity.