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

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.

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.

Asthma patients with obesity had lower predicted FEV₁ 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 FEV₁ and FEV₁/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).

Asthma patients with obesity had lower FEV₁ 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.