Background Sarcoidosis is a granulomatous disease of unknown cause potentially affecting any organ, and most commonly the lung. Previous studies demonstrate that while smoking is known to cause increased airway obstruction over time, bronchovascular bundle thickening which is a radiological pattern of irregular nodular thickening in peri-vascular and lymphatic distribution suggestive of granuloma formation along the airways. Additive effects of smoking and pulmonary sarcoidosis on increasing airway obstruction over time have not yet been investigated. A better understanding of this phenomenon could help predict outcomes for patients and possibly lead to more personalized approaches to treatment.
Methods A retrospective study of pulmonary function tests (PFT) from 22 ever smokers and 27 never smokers with biopsy-supported pulmonary sarcoidosis of greater than one year duration. Changes over time for FEV1, FVC, FEV1/FVC, FEF 25-75, RV, TLC, and DLCO (all expressed as percent predicted) were evaluated. The number of days between each subsequent PFT and initial PFT as well as the slope of change per day was calculated for each case and then converted to show changes per year.
Results There were significant baseline differences in PFTs between the two groups. There was, however, a significant difference in % predicted FEV1/FVC over time, with smokers showing an overall decrease, -1.21±2.69%/year, and nonsmokers showing an increase, 2.85±6.40%/year (p=0.0079). There was also a statistically non-significant difference showing a drop in FEF 25-75 with smokers, -3.82±16.03%/year, and an increase in FEF 25-75 with nonsmokers, 8.11±25.27%/year (p=0.061). In both groups, there were similar increases in FEV1 (p=0.63), FVC (p=0.30), RV (p=0.54), and TLC (p=0.77) over time. Both groups showed a decrease over time in DLCO (p=0.69). After performing a multivariate analysis that controlled for age, medications, and baseline DLCO, the FEV1/FVC change between the two groups was still significantly different (p=0.035).
Conclusions FEV1/FVC ratio and the FEF 25-75 volume can both be used as indicators of airway obstruction, and therefore it may be concluded that smoking may lead to increases in airway obstruction over time in patients with pulmonary sarcoidosis that is independent of age, medications, or baseline PFTs.
Acknowledgements This research was funded by grant #T35HL105350 from the National Heart, Lung and Blood Institute.
Disclosure of Interest M. Walker: None declared, L. Doughty: None declared, A. Janot: None declared, H. Grewal: None declared, M. Yu: None declared, L. A. Saketkoo Grant/research support from: ACR/EULAR Exchange Awardee, M. Lammi: None declared