Asthma, high BMI, older age up risk of small airway dysfunction

Small airway disfunction can lead to increased airway resistance and visible computed tomography (CT) changes, according to a study. Furthermore, this disease is more common among individuals with advanced age, high body mass index (BMI), childhood cough, and asthma.

The study included 1,327 individuals, among whom 437 (32.9 percent) had small airway dysfunction as confirmed by impulse oscillometry (IOS), based on a cutoff of >0.07 kPa/L/s in the difference between the resistance at 5 Hz vs the resistance at 20 Hz (R5–R20). All participants underwent spirometry and completed a questionnaire. Some of them underwent CT imaging.

Participants with vs without small airway dysfunction were more likely to be older (mean 64.0 vs 59.6 years; p<0.001), never-smokers (35.8 percent vs 30.2 percent; p<0.001), have greater airway resistance and worse lung function as indicated by a larger R5–R20 (0.15 vs 0.03 kPa/L/s; p<0.001), and smaller forced expiratory volume in 1 second to forced vital capacity after bronchodilation (60.2 percent vs 72.6 percent; p<0.001). 

With regard to CT results, small airway dysfunction was associated with higher prevalence rates of emphysema (24.0 percent vs 7.0 percent; p<0.001) and gas trapping (50.1 percent vs 22.6 percent; p<0.001).

On analysis, the odds of small airway dysfunction were high in the presence of older age, high BMI, smoking, childhood cough, and asthma.