1. Prevalence of chronic bronchitis in relation to active smoking, stratified by age. □: nonsmokers; ▒: 1–10 cigarettes per day; ░: 11–20 cigarettes per day; ▪: >20 cigarettes per day.
Prevalence of chronic bronchitis in relation to active smoking, stratified by age. □: nonsmokers; ▒: 1–10 cigarettes per day; ░: 11–20 cigarettes per day; ▪: >20 cigarettes per day. Reproduced from [15] with permission from the publisher.
C. Raherison, and P-O Girodet Eur Respir Rev 2009;18:
©2009 by European Respiratory Society