Increased Asymptomatic Airway Hyper-Responsiveness in Obese Individuals

Objective. Asymptomatic airway hyper-responsiveness (AHR) represents a risk of further accelerated decline in lung function, and of asthma. Due to the fact that rare and contradictory results exist concerning the impact of obesity on BHR, we re-assessed the prevalence of bronchial hyper-responsiveness (BHR) in a large cohort of 60 lean, 84 overweight, and 360 class 1-3 obese non-asthmatic individuals, by coupled plethysmography and spirometry. Methods. Baseline-specific airway conductance (SGaw) and spirometric values were measured and then a methacholine challenge testing (MCT) was performed and considered as positive when a >= 200% increase in specific airway resistance (SRaw = 1/SGaw) was reached. Results. Compared to lean and overweight subjects, obese subjects of any class presented about a twice more frequent AHR (similar to 50% in obese vs. 17 and 26% in lean and overweight subjects, respectively). However, the bronchial sensitivity (methacholine dose doubling SRaw) and the shape of the relationship between SGaw and cumulative methacholine doses were the same in the five groups of individuals. Conclusion. The present data show a more frequent AHR in obese subjects. The association of plethysmography with spirometry, by taking into account the bronchodilator effect of the lung inflation (preceding the expiratory flow measurement) in some individuals, permitted to include some MCT which would have been otherwise excluded.