Pulmonary function, exhaled nitric oxide and symptoms in asthma patients with obesity: a cross-sectional study

BACKGROUND: Obesity is a risk factor for the development of asthma. In patients with obesity the diagnosis of asthma is often based on symptoms, but without objective measurements. Nevertheless, obesity-associated asthma is recognized as a distinct asthma phenotype. Therefore, this study explores lung function and symptoms in asthma patients with and without obesity. METHODS: The Netherlands Epidemiology of Obesity (NEO) study is a population-based cohort study with 6671 participants (aged 45–65 years) of whom 472 had asthma. Of this latter group, linear regression analysis was used to examine differences in lung function and symptoms between asthma patients with (n = 248) and without obesity (n = 224), and between asthma patients with and without increased Fe(NO). Analyses were adjusted for confounders. RESULTS: Asthma patients with obesity had lower predicted FEV(1) and FVC values than patients without obesity [adjusted mean difference (MD) -3.3% predicted, 95% CI -6.5, −0.2; adjusted MD −5.0% predicted, 95% CI -7.8, −2.1]. The prevalence of symptoms was higher in patients with obesity. Asthma patients with obesity and with increased Fe(NO) had lower FEV(1) and FEV(1)/FVC values compared with those with low Fe(NO) (adjusted MD −6.9% predicted, 95% CI -11.7, −2.0; −2.4%, 95% CI -4.6, −0.2). CONCLUSION: Asthma patients with obesity had lower FEV(1) and FVC values than patients without obesity. This suggests that patients with obesity have restrictive lung function changes, rather than obstructive changes. Asthma patients with obesity and increased Fe(NO) showed more obstructive changes. Fe(NO) might help to identify patients with eosinophilic inflammation-driven asthma, whereas patients with low Fe(NO) might have an obesity-associated asthma phenotype in which symptoms are partly caused by the obesity. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12931-017-0684-9) contains supplementary material, which is available to authorized users.