In these genetic association studies of lung cancer and COPD, the amount of cigarettes smoked per day was accounted for in analyses. After including number of cigarettes smoked and other measures of smoking exposure such as pack years smoked, the genetic association with lung cancer and COPD remained. This supports the potential of a direct genetic influence of this region on multiple distinct disorders, nicotine dependence, lung cancer, and COPD, or pleiotropy.
