Asthma

Asthma

• Definition.

Asthma is a chronic, inflammatory disease that affects the respiratory system (lungs and airways).
People who have asthma have hyperactive airways that respond to allergens (things they are allergic to) or irritants (things that produce irritation) by a series of reactions that result in a reduction of the diameter of the airway and thus in airflow limitation, causing the manifestations that will be discussed later.

II-     Burden of disease

The prevalence of asthma appears to have increased continuously since 1970s. It is estimated that asthma affects now 4 to 7 % of people worldwide.
The prevalence is higher in people aged less than 18 years old.
It is higher in males before puberty and in females after puberty.
It is also higher in urban population.
Asthma is the leading cause of hospitalization for children and is the number one chronic condition causing elementary school absenteeism.

III-   Causes

Development of asthma is multifactorial.
There is a genetic susceptibility as shown by the presence of a positive family history in many cases.
But many environmental factors interact as to determine the severity of the disease and the frequency of the attacks
Examples of factors or triggers:

• Household allergens: dust mites, cockroaches, pets, …
• Environmental allergens : pollen, …
• Occupational allergens:  paint, …
• Infections: such as common cold, sinusitis, …
• Exercise (especially in cold or dry environment)
• Emotional stress such as anxiety, anger, excitement…
• Gastro esophageal reflux disease
• Certain medications such as Aspirin, Ibuprofen (trigger > 30 %, especially in people who have nasal polyps). 

IV-     Mechanism of Action.

When an asthmatic is exposed to an irritant or allergen:

• The airway constricts ( i.e. narrows )
• The airway gets inflamed and swells
• An excessive amount of mucus is secreted by the lining of the airway ; this clogs the airways and further blocks them
• The muscles around the airways contract and spasm , causing more narrowing

     V -      Symptoms

          The narrowing of airways results in symptoms such as:

• Coughing
• Wheezing
• Chest tightness
• Shortness of breath
• Decreased exercise tolerance

     Between episodes, most patients feel well or have mild symptoms especially after exercise.

  VI- Diagnosis

  In order to make a diagnosis of asthma, doctors will gather information from personal and family history and from the physical exam. They might need to confirm it by a test called “spirometry”. They might also need to diagnose a possible underlying cause (such as pneumonia) and to exclude other diseases that might cause wheezing (such as a foreign body -like a peanut- getting accidentally lodged in the lungs).

• Prognosis

Asthma is resolved in most children afflicted with the disease. However, about 25% of children continue to experience the symptoms of asthma (like wheezing) into adulthood, or they may have relapse (i.e. symptoms of asthma occurring again after a disease-free period).

• Treatment

Treatment consists of controlling triggering factors and using certain medications.

• Control of triggering factors :
• Use of synthetic fiber pillows
• Use of impermeable mattress covers
• Frequent washing of bed sheets , pillow cases and blankets in hot water
• Removal of upholstered furniture , soft toys , pets and carpets ( dust mites , animal dander )
• Use of dehumidifiers , especially in poorly aerated rooms ( molds )
• Elimination of cockroach exposure by house cleaning or extermination
• Steam treatment of homes to decrease dust mite allergens
• Avoidance of cigarette smoke, strong odors, irritant fumes, cold temperature, high humidity, certain medications…

• Medications.

They can be taken orally or inhaled. Some of them act on the bronchoconstriction or narrowing of the airways and are called bronchodilators. Others act on the inflammation (like corticosteroids, leukotriene inhibitors  ...)