Inflammation and Treatment in Asthma and COPD

By James F. Donohue, MD, FCCP; and Jill A. Ohar, MD, FCCP

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Asthma

Significance

The prevalence of asthma has increased dramatically in the United States over the past 30 years. The mortality rates also increased until they reached a plateau recently. Mortality is especially high in African Americans (38.5 vs 15.1 per million in Caucasians) and it is also high in Hispanics of Puerto Rican heritage (40 per million). Asthma was estimated to affect more than 10.2 million adults during 1996. Direct and indirect costs associated with asthma during 1998 were $12.7 billion. A recent report from the 2000 Behavioral Risk Factors Surveillance System estimates that approximately 7.2% of adults residing in the United States have asthma. The prevalence of asthma decreases with increasing family income. The prevalence is 9.8% among people with family incomes of < than $15,000 and 5.9% among those with incomes > $75,000. Women had higher prevalence rates of asthma than men (9.1 vs 5.1%).³

For unclear reasons, more affluent Western countries have higher prevalence rates than impoverished nations, giving rise to the "health hygiene hypothesis." The basic tenet is that the immune system of the newborn infant is skewed toward subtype 2 helper T (Th²) cells and needs timely and appropriate environmental stimuli to create a balanced immune response with subtype 1 helper T (Th₁) cells. The presence of older siblings, early exposure to day care, tuberculosis, measles or hepatitis A infection, or living in a rural environment are factors that favor the Th₁ phenotype. The Th₂ allergic, asthmatic phenotype is favored by the widespread use of antibiotics, Western lifestyle, living in an urban environment, a diet high in sodium and fat, plus sensitization to house dust mites and cockroaches.

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