According to the Centers for Disease Control and Prevention (CDC), smoking is the primary risk factor for chronic respiratory diseases, such as emphysema and chronic bronchitis, both of which are major conditions of COPD. In addition, more than 126 million non-smoking Americans continue to be exposed to secondhand smoke in homes, vehicles, workplaces, and public places. Nationally, nearly 60 percent of U.S. children ages 3 – 11 years are exposed to secondhand smoke. Direct or secondhand exposure to tobacco smoke is therefore a key risk factor for CLRD.
The figure below summarizes the various risk factors associated with CLRD. It is important to note that there are two classes of risk factors associated with lower respiratory diseases: those that are a direct cause of disease (e.g., cigarette smoking among those with emphysema) and those that worsen or serve as a trigger for existing disease (e.g., exposure to allergens among those with asthma).