Asthma

Asthma is a disease of the lung’s airways. About 1 person in 40 is the world has asthma. Its prevalence and severity among children has increased steadily in the past 40 years. A World Health Organization report indicates that 10 to 15 % of children in the world suffer from the disease. In Malaysia a clinical survey done in 1997 of school children aged 7 to 12 years in the Kelang Valley showed that 17 % had asthma but in many cases their parents were not aware of their children’s condition. Asthma is defined as follows:

1. 2. 3. Airways obstruction that is reversible (but not completely in some individuals) either spontaneously or by treatment; the presence of inflammation in the airways mucosa by inflammation-causing cells such as eosinophils, mast cell, macrophages, and T-lymphocytes; and increased airway responsiveness to a variety of stimuli. The abnormal hyperactivity of the airway may be caused by many non-specific stimuli including: aero-irritants (cigarette smoke, diesel fumes, nitrous oxide and others), weather changes, stress, drugs (aspirin, antibiotics and others), emotions and viral infections.

These stimuli cause increased production of mucus and contraction of the bronchial muscles resulting in difficulty in breathing out. Asthmatic individuals develop clinical symptoms such as chronic cough, wheezing and hoarse voice, after exposure to allergens, environmental irritants, viral infections, cold air or exercise. Asthma may be broadly grouped into allergic asthma and non-allergic asthma. Some asthmatics may have both types. In Malaysia about 80 to 90% are allergic asthma mostly noted in children and young adults, and 20% are non-allergic asthma that is frequently found in middle-aged and elderly individuals. In allergic asthma, inhalation of allergens such as house dust mites, cockroach or cat dander, is the most important stimulus known to trigger the disease. In sensitized individuals the allergens trigger an immediate asthmatic response during which bronchi-constriction develops within 10 minutes, reaches maximal contractions in 30 minutes and then usually resolves in 1 to 3 hours. In about 50% of adults and 80% of children with the response, a late asthmatic response (bronchi-constriction) follows. The asthmatic attack recurs at 3 hours and lasts for 24 hours if untreated. Patients with late phase asthma triggered by allergens, go on to develop hyper-responsiveness that last for days or weeks. From the Malaysian context, analysis of the response to specific allergens in children with asthma showed that 90% reacted to house-dust mites allergens, 67% reacted to cockroach allergens, 23% to cat dander or dog epithelium allergens, and 10 to 22% to cows milk, soya bean, egg, peanut, fish, shrimp, crab, banana, and wheat. Thus, it is important to obtain a complete allergen profile for the asthma patient so that appropriate avoidance measures can be taken as part of the management programme for the disease. Two approaches are needed for the successful management of the asthma, namely, non-pharmacological reduction of risk factors and pharmacological intervention through medication. Bronchoconstriction is reversed by long acting bronchodilators (e.g. Salmeterol, formoterol) and may be used in children greater than 5 years old. As the disease progresses, exacerbation caused by inflammation of the bronchial mucosal tissue, specifically eosinophils, is an early and important feature of asthma. Thus, anti-inflammatory drugs specifically inhaled corticosteroids (e.g. nebulized budesonide) are widely used for the long-term control of asthma.