risk factors for asthma

Risk factors for asthma:

1. Constitutional factors: predisposes the person to development of asthma or particular outcomes of asthma.

a. Family history: Although asthma is not a hereditary disease, but having parents with asthma history predisposes the offspring with high probability to get the disease due to genetic inheritance.

b. Genetic mutations: Studies showed that a specific gene may have been associated with asthma development. The gene, ADAM33 is located on chromosome 20 and is expressed in lung and muscle cells. Mutations on this gene may predispose the person to having asthma. The gene causes airways to over-respond and constrict airway passages.

c. Gender: Males are more susceptible to get asthma after birth compared to females. The reason may be due to the fact that a man’s airway size is smaller compared to a woman. However, the percentages drops as males grow up, and at around the age of 20, the rates are similar for both genders. After the age of 40, females tend to have higher chances to get the disease compared to males.

d. Allergic (atopy) predisposition: Atopy is allergic hypersensitivity to different parts of the body that do not come in contact with allergens, but triggers allergic reactions (anaphylaxis). Studies showed that many children with eczema during when they are young have higher chances to develop asthma.

2. Environmental exposures or other factors: associated with increased risk of acquiring asthma or having certain outcomes of the disease.

a. Exercise: exercise can induce asthma for people who are more sensitive to changes in temperature and humidity of the air. When resting, the person breathes through nose that serves to warm and humidify the air inhaled. However, when exercising, the person tends to breathe through mouth and the air being inhaled is colder and drier. The difference between the humidity of air in lungs and the inhaled ones triggers the allergic reaction. Airway begins to swell and secrete large amount of mucous. This obstructs the airway, making it difficult to breathe and thus, leads to asthma (COPD).

b. Viral infections: viral infections activate eosinophils that readily gathered along the nerves in the lungs. This will then cause eosinophils to release a protein called major basic protein (MBP) which has been discovered to block the action of M2 receptors and keeps the receptors from turning off Ach release. High Ach leads to increased constriction of the airways.

c. Irritants (smoking, pollutants): smoking damages cilia in the airways, preventing the cilia from performing their normal function, clear mucous and dust out of the respiratory system. Smoking also cause lungs to secrete more mucous than normal, resulting in marked increase in mucous accumulation in the airways, obstructing the air pathway.

d. Allergies: hypersensitivity due to exposure to a particular allergen resulting in marked increase in reactivity to that antigen on subsequent exposure. Among the common allergens are: dust mites, fungi, animal proteins, fur.

e. Pregnancy: Mothers who smoke during pregnancy can lead to having infants with lower pulmonary function compared to those who are not.