Background: Several studies have demonstrated an association between obesity and asthma. However, it is uncertain if fraction of exhaled nitric oxide (Feno), which is used as a marker of airway inflammation, and atopy are associated with BMI. The aim of this study was to examine if obese subjects with asthma symptoms have a different phenotype of asthma than nonobese subjects as indicated by Feno.
Methods: The subjects (N = 2,187) consisted of women and men, aged 25 to 74, living in Gothenburg, Sweden, who participated in the randomly selected INTERGENE study cohort. Measurements included anthropometric measures, bioelectric impedance, Feno, pulmonary function, and blood samples for IgE; questionnaires included items on respiratory symptoms. Obesity was defined as BMI ≥ 30 kg/m(2). In this cross-sectional analysis, general linear models were used to analyze how Feno was associated with anthropometry, body composition, wheezing, and atopy.
Results: In nonobese subjects, wheezing was associated with raised Feno and atopy, whereas in contrast, obese subjects who reported wheezing had lower Feno than obese subjects without wheezing (16.1 vs 19.1 parts per billion, P < .01). The prevalence of atopy was similar in both of those subgroups (25.0% vs 20.7%, P = .4). Similarly, in 395 subjects (19%) who reported wheezing, Feno was negatively associated with BMI, waist-to-hip ratio, and percentage of body fat, whereas no significant relationships were observed in those without respiratory symptoms.
Conclusions: Wheezing was significantly associated with reduced Feno in obese subjects, whereas there was a positive association between wheezing and Feno among the nonobese subjects, indicating a possible difference in asthma phenotype, based on body weight.