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


METHODS
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 (FEV(1)), functional residual capacity/total lung capacity (FRC/TLC)], inflammatory markers [blood eosinophils, sputum eosinophils and neutrophils, exhaled nitric oxide (FE(NO)), 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.


RESULTS
Obese patients (n = 29) had a higher FEV(1)%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 FE(NO) (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).


CONCLUSIONS
Obesity in patients with difficult-to-treat asthma is inversely related with sputum eosinophils and FE(NO), 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.
van Veen
I H
IH
Department of Pulmonology, Medisch Spectrum Twente, Enschede, The Netherlands.
Ten Brinke
A
A
Sterk
P J
PJ
Rabe
K F
KF
Bel
E H
EH
D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000188:drug therapy / Q000209:etiology* / Q000503:physiopathology*; D015992:Body Mass Index; D004804:Eosinophils; D005260:Female; D005764:Gastroesophageal Reflux; D006801:Humans; D007249:Inflammation / Q000209:etiology / Q000276:immunology; D008168:Lung / Q000276:immunology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D009765:Obesity / Q000150:complications*; D012129:Respiratory Function Tests; D012307:Risk Factors; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes; D013183:Sputum / Q000276:immunology
D009569:Nitric Oxide