Changes in prevalence of chronic obstructive pulmonary disease and asthma in the US population and associated risk factors.

Chronic lower airway diseases, including chronic obstructive pulmonary disease (COPD) and asthma, are currently the third leading cause of death in the United States. We aimed to evaluate changes in prevalence of and risk factors for COPD and asthma among the US adult population. We evaluated changes in prevalence of self-reported doctor-diagnosed COPD (i.e. chronic bronchitis and emphysema) and asthma and self-reported respiratory symptoms comparing data from the 1988-1994 and 2007-2010 National Health and Nutrition Examination Surveys. To investigate changes in the severity of each outcome over the two periods, we calculated changes in the proportions of spirometry-based airflow obstruction for each outcome. Prevalence of doctor-diagnosed chronic bronchitis and emphysema decreased significantly mainly among males, while asthma increased only among females. The self-reported disease and the respiratory symptoms were associated with increased prevalence of airflow obstruction for both periods. However, the prevalence of airflow obstruction decreased significantly in the second period among those with shortness of breath and doctor-diagnosed respiratory conditions (chronic bronchitis, emphysema, and asthma). COPD outcomes and asthma were associated with lower education, smoking, underweight and obesity, and occupational dusts and fumes exposure. Chronic lower airway diseases continue to be major public health problems. However, decreased prevalence of doctor-diagnosed chronic bronchitis and emphysema (in males) and decreased prevalence of airflow obstruction in those with respiratory symptoms and doctor-diagnosed respiratory diseases may indicate a declining trend and decrease in disease severity between the two periods. Continued focus on prevention of these diseases through public health interventions is prudent.