Airway wall thickness on HRCT scans decreases with age and increases with smoking

BACKGROUND To investigate if age, gender and smoking are associated with airway wall thickness (AWT) measured by high resolution computed tomography (HRCT) and if higher AWT is associated with lower levels of pulmonary function in healthy current- and never-smokers with a wide age range. METHODS HRCT scans were performed in 99 subjects (48 never- and 51 current-smokers, median age 39 years [IQR 22 - 54], 57% males). The AWT at an internal perimeter of 10 mm (AWT Pi10) was calculated as an overall measurement of AWT, based on all measurements throughout the lungs. Extensive pulmonary function testing was performed in all subjects. RESULTS Higher age was associated with a lower AWT Pi10 (b = -0.003, p < 0.001). Current-smokers had a higher AWT Pi10 than never-smokers (mean 0.49 mm versus 0.44 mm, p = 0.022). In multivariate analysis, age and current-smoking were independently associated with AWT Pi10 (age b = -0.002, p < 0.001, current-smoking b = 0.041, p = 0.021), whereas gender was not (b = 0.011, p = 0.552). Higher AWT Pi10 was associated with a lower FEV1, FEV1/FVC, FEF25-75 and higher R5, R20 and X5. CONCLUSIONS AWT decreases with higher age, possibly reflecting structural changes of the airways. Additionally, current-smokers have a higher AWT, possibly due to remodeling or inflammation. Finally, higher AWT is associated with a lower level of pulmonary function, even in this population of healthy subjects. TRIAL REGISTRATION This Study was registered at www.clinicaltrials.gov with number NCT00848406 on 19 February 2009.