Due to their typically heavy lifetime smoking exposures, potentially related to (at least in part) enrichment in genetic variants responsible for nicotine addiction, COPD subjects can be considered as a unique population for studying smoking behaviors. However, diagnosis and further progression of COPD are likely to modify smoking status (i.e. increased efforts to quit smoking) and smoking intensity (e.g. reduction of CPD). Identifying genetic factors involved in smoking cessation is of special importance in clinical practice, since quitting smoking may reduce subsequent loss of lung function in COPD patients.1314 Smoking cessation results in an improvement of respiratory symptoms in COPD patients, and is associated with reduced mortality due to COPD.13–16 Another smoking-related phenotype, age at smoking onset, correlates with nicotine dependence in adulthood 17 and mortality due to COPD.15 Taken together, it is of special interest to search for markers associated with smoking behaviors uniquely among COPD patients. Likewise, it is of importance to assess whether SNPs, regarded as established genetic determinants of smoking cessation and CPD in other populations, associate with these traits in COPD patients as well. Identification
