COPD is influenced by genetic and environmental factors and the interaction between genetic and environmental influences are likely to be important in the pathogenesis of COPD.[25] Cigarette smoking is the major environmental determinant of COPD and genetic and smoking interactions have been associated with lung function in COPD and other chronic lung diseases.[26]–[29] We found effects of genetic variants in AQP5 are stronger in continuous smokers than among those who have quit smoking or smoke intermittently. The gene discussed is AQP5; the disease is chronic lung disease.