Computed tomography-quantified emphysema distribution is associated with lung function decline

Emphysema distribution is associated with chronic obstructive pulmonary disease. It is, however, unknown whether computed tomography (CT)-quantified emphysema distribution (upper/lower lobe) is associated with lung function decline in heavy (former) smokers. 587 male participants underwent lung CT and pulmonary function testing at baseline and after a median (interquartile range) follow-up of 2.9 (2.8-3.0) yrs. The lungs were automatically segmented based on anatomically defined lung lobes. Severity of emphysema was automatically quantified per anatomical lung lobe and was expressed as the 15th percentile (Hounsfield unit point below which 15% of the low-attenuation voxels are distributed (Perc15)). The CT-quantified emphysema distribution was based on principal component analysis. Linear mixed models were used to assess the association of emphysema distribution with forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC), FEV1 and FVC decline. Mean +/- SD age was 60.2 +/- 5.4 yrs, mean baseline FEV1/FVC was 71.6 +/- 9.0% and overall mean Perc15 was -908.5 +/- 20.9 HU. Participants with upper lobe-predominant CT-quantified emphysema had a lower FEV1/FVC, FEV1 and FVC after follow-up compared with participants with lower lobe-predominant CT-quantified emphysema (p=0.001), independent of the total extent of CT-quantified emphysema. Heavy (former) smokers with upper lobe-predominant CT-quantified emphysema have a more rapid decrease in lung function than those with lower lobe-predominant CT-quantified emphysema.