PURPOSE: We investigated the relationship between airway dimensions and airflow obstruction and respiratory quality of life in current and former cigarette smokers. METHOD AND MATERIALS:
Cigarette smokers were studied that enrolled in the COPDGene study. Spirometry assessment included forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), % predicted FEV1 (FEV1%-p), % predicted FVC (FVC%-p), and peak expiratory flow (PEF). Respiratory quality of life was assessed by the St George's Respiratory Questionnaire (SGRQ) score and 6 Minute Walking Distance (SMWD). Inspiratory CT was available to extract the airways, the amount of emphysema, and the total lung capacity (TLC). Lumen perimeters and airway wall areas were automatically extracted perpendicular to the airways. Linear regression was performed on these measurements to calculate an index score of airway wall thickness, expressed as the square root of wall area at airways with a perimeter of 10mm (Pi10). Emphysema was defined as the percentage of low-attenuation area below -950 HU (LAA%-950). Multiple linear regression was used to determine the predictive value of Pi10 and smoking status on airflow obstruction and respiratory quality of life. An interaction was included in the model to investigate if the effect of Pi10 differed by smoking status. All models were adjusted for age, gender, body mass index, pack years, bronchodilator responsiveness, TLC, and LAA%-950. RESULTS: 1544 cigarette smokers (894 former smokers) were included, with a mean age of 60.7 A-A?A 1/2 8.9 years and a mean Pi10 of 2.23 A-A?A 1/2 0.57mm. Pi10 was significantly associated with all airflow obstruction and respiratory quality of life measures (all p<0.001). The interaction between Pi10 and smoking status was significant for all measures except FVC%-p (p=0.30) and SGRQ score (p=0.064). This indicates that the effect of Pi10 on FEV1%-p, PEF, FEV1/FVC and SMWD was significantly reduced in current smokers compared to former smokers. CONCLUSION: Pi10 independently contributes to airflow obstruction and respiratory quality of life. This effect is stronger in former smokers as compared to current smokers. CLNICAL RELEVANCE/APPLICATION: Pi10 is an independent marker for airflow obstruction and respiratory quality of life and may be more strongly associated with these outcomes in former smokers than current smokers.