Registered Nurses' Association of Ontario

Prevalence and Definition

Prevalence of Asthma

  • Asthma is the most common chronic illness affecting children
  • Asthma affects 2.3 million Canadians over the age of 4 years with an estimated total cost of between $504 million and $648 million in 1991.
  • It accounts for more missed school days and limitations in daily activities than any other childhood illness
  • In Ontario, 10 to 13 % of children from birth to 18 years have asthma.
  • Asthma is one of the main reasons children are admitted to hospital and is also one of the main reasons children are seen repeatedly in the emergency department.


Asthma, a chronic inflammatory disorder of the airways. It is characterized by paroxysmal or persistent symptoms such as

  • dyspnea
  • chest tightness,
  • wheezing,
  • sputum production and
  • cough associated with variable airflow limitation and a variable degree of airway hyper-responsiveness to triggers.

An asthma episode may begin suddenly, or may have a slow onset with a gradual worsening of symptoms.

These episodes, which can last for a few minutes to several days, are attributed to a hyper-responsiveness of the airways and are typically reversible.

Women and Children
Promoting Asthma Control in Children
Background Information