Clinical features and 1-year outcomes of variable obstruction in participants with preserved spirometry: results from the ECOPD study in China

Background There are limited data on the clinical features and longitudinal prognosis of variable obstruction, particularly among never smokers and different variable obstruction types. Therefore, we aimed to evaluate the clinical characteristics of the participants with variable obstruction and determine the relationship between variable obstruction and the development of chronic obstructive pulmonary disease (COPD) and the decline of lung function in a community-dwelling study of Chinese, especially among never smokers and different variable obstruction subtypes. Methods Participants with preserved spirometry (postbronchodilator forced expiratory volume in 1 s (FEV 1 )/forced vital capacity (FVC) ≥0.70) at baseline from the Early COPD cohort were included in our analysis. Participants with variable obstruction (prebronchodilator FEV 1 /FVC <0.70) were compared with those without variable obstruction (prebronchodilator FEV 1 /FVC ≥0.70). We performed subgroup analyses in never smokers, former and current smokers, and different variable obstruction types (postbronchodilator FVC <prebronchodilator FVC or postbronchodilator FVC ≥prebronchodilator FVC). Results The final analysis included 1140 participants with preserved spirometry (169 in the variable obstruction group) at baseline. Participants with variable obstruction were older, had lower lung function and had greater severe emphysema and computed tomography-defined air trapping than participants without variable obstruction. Participants with variable obstruction had a significantly increased risk of incident spirometry-defined COPD (relative risk: 3.22, 95% confidence interval 2.23 to 4.64, p <0.001) than those without variable obstruction after adjustment for covariates. These findings remained consistent among both former and current smokers, never smokers, and different variable obstruction types. Additionally, participants with variable obstruction had a faster decline in postbronchodilator FEV 1 /FVC (2.3±0.5%/year vs 0.9±0.4%/year, mean difference: 1.4 (95% confidence interval 0.5 to 2.3), p=0.002) than participants without variable obstruction after adjustment for covariates. Conclusions The results of our study revealed that variable obstruction can identify individuals who are at risk for the development of COPD and accelerated postbronchodilator FEV 1 /FVC decline in preserved spirometry.