Etiology of Asthma

The complete causes of asthma are unknown. Heredity does seem to play a role as do allergens and environmental factors. According to the latest Expert Panel Report (EPR) in 1997 from the National Heart, Lung, and Blood Institute's National Asthma Education and Prevention Program, "Atopy, the genetic predisposition for the development of an IgE-mediated response to common aeroallergens, is the strongest identifiable predisposing factor for developing asthma." There are two categories of asthma: allergic or extrinsic and idiosyncratic or intrinsic. Allergic asthma is a result of an antigen\antibody reaction on mast cells in the respiratory tract. This reaction causes the release of inflammatory mediators from mast cells which elicit the clinical response associated with an asthma attack. Idiosyncratic asthma is a result of neurological imbalances in the autonomic nervous system (ANS) in which the alpha and beta adrenergic as well as the cholinergic sites of the ANS are not properly coordinated.

Onset of asthma between the ages of 5 to 15 years usually indicates asthma with an allergic basis. According to Adams and Marano, CDC 1995, asthma affects an estimated 4.8 million children and is the most common chronic disease of childhood. If onset occurs later in life, asthma is more likely idiosyncratic. The incidence of asthma in the population below the age of 15 years is 5% to 15%. An incidence of 1% is found in the adult population.