Lung function, FE_no, symptoms and obesity in asthma – A cross-sectional study

Background: Obesity increases the risk of asthma. Obesity-related asthma is recognized as a distinct phenotype. More evidence on differences between obese and non-obese asthma patients can help to improve diagnostic accuracy and to optimize treatment. Aim: To explore differences in lung function, inflammation and symptoms between obese and non-obese asthma patients. Method: The Netherlands Epidemiology of Obesity (NEO) study is a population based cohort study in 6671 participants(592 with asthma). Differences in lung function, fractional exhaled nitric oxide(Fe_NO) and symptoms between obese and non-obese asthma patients were explored using regression analysis, corrected for age, sex, smoking, ethnicity, education, physical activity, inhaled corticosteroids use. Results: Among 592 asthma patients, 318 were obese(BMI≥30 kg/m²). Non-obese asthma patients had better predicted forced expiratory volume in 1s (FEV₁%)(100.2±18.6 vs. 96.5±18.1,p=0.026) and forced vital capacity (FVC%)(112.1±18.0 vs. 107.0±15.8,p<0.001) compared with obese patients. They did not differ regarding Fe_NO(17[12-25] vs. 15[11-24]ppb,p=0.285). Obese patients reported more wheezing than non-obese patients(33.3% vs. 16.9%,p<0.001), but did not differ on other symptoms. Symptoms worsened more during exercise in obese patients compared with non-obese patients(47.0% vs. 31.9%, p<0.001). Conclusions: Non-obese asthma patients have a better lung function than obese asthma patients. Obese patients more often experience wheezing and their symptoms worsen more during activity. Our results suggest that despite similar levels of inflammation as assessed by Fe_NO, obese asthma patients are more symptomatic and have a lower lung function than non-obese patients.