Lung Diseases

Asthma

About 300 million people worldwide suffer from asthma, a chronic disease marked by bouts of breathlessness and wheezing, and in 2005, about 255,000 people died from [Page 263]asthma. Asthma is the most chronic disease among children, and it occurs in all countries of the world. Over 80 percent of deaths from asthma occur in low- and lower-middleincome countries, in part because of the lack of medical care and pharmaceutical intervention (e.g., inhaled corticosteroids) available to many in those countries.

Exposure to allergens is the greatest risk factor for developing asthma, and inhaled allergens seem to be the most harmful. Some allergens are naturally occurring substances like pet dander, pollen, and molds, while others are created by human activity, including tobacco smoke and other air pollutants. Urbanization is associated with an increase in asthma; although the exact mechanism has not been determined, some theorists think it could be due to greater exposure to air pollution (e.g., from automobiles and other motorized vehicles). Because many cases of asthma go undiagnosed, it is also possible that greater access to healthcare in cities results in previously ignored cases being diagnosed.

In the United States, according to the 2007 National Health Interview Survey, 11.5 percent of Americans suffer from asthma. The prevalence of asthma varies with age, being highest in the late teenage years (16.9 percent for people age 15–19) and lowest in early childhood (8 percent for children under age 5). In adulthood the prevalence is similar for men and women, but in childhood (under age 18) it is more common in boys than girls (14.7 percent versus 11.3 percent). Asthma is somewhat related to race and ethnicity—blacks have higher rates than whites (13.2 percent versus 11.5 percent) and Puerto Ricans have an even higher prevalence (20.3 percent)—and it is higher for people living below the poverty threshold than above it.

Chronic Obstructive Pulmonary Disease

About 210 million people worldwide are believed to suffer from chronic obstructive pulmonary disease (COPD), a lung disease in which airflow is blocked from the lungs, and in 2005, over three million people died of it (about 5 percent of all global deaths). Most COPD deaths (90 percent) occur in low- and middle-income countries, and although historically COPD has been more common in men, as more women worldwide have taken up cigarette smoking, the rates have become more equal between the genders. COPD includes emphysema and chronic bronchitis, terms no longer used by the World Health Organization (WHO), and is characterized by breathlessness, a chronic cough, and abnormal sputum (matter expelled from the respiratory tract).

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