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Childhood Asthma

Are there any risk factors for asthma?

  • The most important "risk factor" for asthma is probably whether allergic diseases run in the child's family. Children can inherit an increased likelihood of having an allergic disease from parents who have allergic diseases, or whose families have allergic diseases. "Allergic diseases" which run in families include Asthma, Hay Fever (or Allergic Rhinitis), Eczema, Hives (or Urticaria), and certain food allergies. Often, there is no particular pattern of inheritance — for example, a parent might have Hay Fever, and have 1 child with asthma, another child with eczema, and a third child with no allergic diseases at all. Individuals in familes with allergic diseases are more prone to have cells which release chemicals causing local inflammation and allergic reactions in response to allergic and irritant triggers
  • Smoking in the home increases the risk of asthma. This is important, because prohibiting smoking in the house is such a simple way of reducing the risk that a child has asthma.
  • Asthma is more common in children who were born prematurely (before 36 weeks gestational age). This is true even if the child didn't have much in the way of lung disease as a premature baby.

Can a child with asthma outgrow it?

Even though asthma is a potentially dangerous disease, with good treatment, most Canadian children with asthma do well. The best studies on long-term outcome in asthma come from Australia. These studies show that about 2/3 of children with asthma outgrow it — sometime before or around puberty. In a small number of these people, asthma comes back later in adult life. In most of the remaining 1/3 of patients, their asthma improves as they grow older. In only about 10% of children with asthma will their asthma continue to be a major problem as they enter adult life.

Asthma research has suggested that there may be 2 different forms of asthma in young children.

  • In one type, children are born with relatively small airways, and when these airways are narrowed further by a viral respiratory infection, asthma symptoms can result. Children appear to be more likely to be born with relatively small airways if their mother smoked during the pregnancy. As the child grows, the airways become bigger and viral infections are less likely to cause enough airway narrowing to lead to asthma symptoms. Thus, children with this form of asthma tend to have symptoms during viral infections such as colds, and their asthma tends to resolve later on in childhood.
  • In the other type of childhood asthma, children tend to have allergic diseases such as asthma, hay fever, and eczema. These children have asthma symptoms when exposed to substances they are allergic to, such as pollens and animals, and they often have similar reactions leading to asthma symptoms during viral respiratory infections. These children have probably inherited their tendency to have allergic disease(s) from their parents. They are more likely to continue having allergic diseases such as asthma and hay fever as they grow older, and they are less likely to outgrow their asthma.

Long-term outcome of Asthma

Recent research suggests that people with severe, chronic asthma may be at increased risk of developing Chronic Obstructive Lung Disease (COPD), especially after 50 years of age. COPD typically occurs in smokers. This is another reason why people with asthma should never smoke – even as adults. It would seem reasonable to also avoid, whenever possible, occupations with heavy exposure to dusts or fumes. 

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