Impaired exercise capacity in individuals with non-obstructive small airway dysfunction

Whether individuals with non-obstructive spirometry-defined small airway dysfunction (SAD) have impaired exercise capacity is unclear, particularly in never-smokers. This study clarifies the degree of impaired exercise capacity and its potential cause in individuals with non-obstructive SAD.

This community-based, multiyear cross-sectional study analyzed data collected in Guangdong, China from 2012-2019 by the National Science and Technology Support Plan Program. Measurements of exercise capacity [peak work rate and peak oxygen uptake ( $$ )] in participants with non-obstructive spirometry-defined SAD (n=157) were compared with those in controls (n=85) and Global Initiative for Chronic Obstructive Lung Disease (GOLD) I patients (n=239). Subgroup analyses were performed by smoking status.

The risk of impaired exercise capacity was significantly higher in participants with non-obstructive SAD [ $$ <84%predicted, adjusted odds ratio (aOR) =2.53; 95% confidence interval (CI): 1.42-4.52] than in controls but was not significantly different from that in GOLD I patients. Results were consistent within subgroups of smoking status (ever-smokers: non-obstructive SAD vs. controls, aOR =2.44; 95% CI: 1.08-5.51; never-smokers: non-obstructive SAD vs. controls, aOR =2.38, 95% CI: 1.02-5.58). Participants with non-obstructive SAD had a significantly lower peak work rate (β=-10.5; 95% CI: -16.3 to -4.7) and $$ (%predicted, β=-4.0; 95% CI: -7.7 to -0.2) and tended to have higher ventilatory equivalents for carbon dioxide at the ventilatory threshold ( $$ , β=1.1; 95% CI: -0.1 to 2.3) when compared with controls. Both peak work rate and $$ were negatively correlated with $$ .

Although not meeting the current criteria for chronic obstructive pulmonary disease, individuals with non-obstructive SAD have impaired exercise capacity that may be associated with ventilatory inefficiency regardless of smoking status.