Chronic inflammatory lung diseases like chronic bronchitis and emphysema are a major global health problem, and the fourth leading cause of death and disability in developed countries, with smoking accounting for 90% of the risk for developing them.

Smoking is a known risk factor for respiratory diseases like chronic bronchitis, but genes also play a significant role in its development, according to researchers in Sweden, who studied more than 40,000 Swedish twins to determine the extent to which behavior, environment and genes each play a role ion the development of chronic bronchitis.

Some people have a genetic variation that makes them more susceptible to chronic obstructive pulmonary disease (COPD) if they smoke tobacco, according to new research from Wake Forest University School of Medicine and colleagues.