The relationship between exhaled nitric oxide and body mass index in controlled an uncontrolled Tunisian asthmatics

Abstract

Background Several studies have demonstrated a causal link between asthma and obesity. Investigations of the relationship between body mass index (BMI) and exhaled nitric oxide (eNO), a marker of eosinophilic airway inflammation in asthmatics, have produced conflicting results. The influence of obesity on eNO in controlled versus uncontrolled asthmatics is unidentified. Objective We aimed to evaluate the relationship between BMI and eNO in a sample of controlled and uncontrolled Tunisian asthmatics. Methods It was a cross sectional study including adult patients treated for asthma. All patients completed an Asthma Control Test and underwent testing for eNO and spirometry. Obesity was defined as a BMI≥30 Kg/m 2 . Results The mean age for the 148 asthmatics enrolled was 44.2 ± 14.7years. Controlled asthma was diagnosed in 71.7% of patients and uncontrolled asthma in 28.3%. Obesity was present in 20% of patients. Obese asthmatics had a higher eNO than non obese (32.5 vs 29.4 ppb, p=0.5). Among uncontrolled asthma, mean eNO level was higher in obese patients than in non obese (50.4 vs 38.3 ppb, p=0.4). However, eNO of obese patients was not different from non obese patients in controlled asthmatics (28.4 vs 26.8 ppb, p=0.7). Pearson9s rank correlation coefficients revealed no correlation between eNO and BMI in controlled asthmatics. However, there was a very weak negative correlation between eNO and BMI in uncontrolled asthmatics (r=-0.05, p=0.7). Conclusion Our data show that in people with established asthma, there is no relationship between BMI and eNO. Obesity is not associated with eosinophilic airway inflammation, neither in controlled, nor in uncontrolled asthmatics.