From: Reversible and permanent effects of tobacco smoke exposure on airway epithelial gene expression
 | Never | Former | Current |
---|---|---|---|
n | 21 | 31 | 52 |
Age | 32.3 (10.7) | 55.9 (14.7) | 48.6 (15.2) |
Pack years | Â | 34.0 (30.1) | 34.5 (34.2) |
Months since quitting | Â | 145.2 (162.82) | Â |