Causes of Asthma
It has been estimated that there are about 300 million of people affected by asthma all over the world. Among the big numbers, about 22 million are in the USA. People ranging from all ages may have asthma, but this disease usually starts from the childhood. Today, there are nearly 6 million of children are suffering from asthma in the United States. And asthma causes approximately 255,000 deaths each year in the world.
For most children, asthma has become one of the most commonly chronic diseases, particularly for those who were born in low weight, or those who are often exposed to cigarette smoke or brought up in low level economic environment. Generally, asthma symptoms will occur on children at the age of five for the first time. The symptoms often start with frequent episodes of wheezing together with respiratory infections. In addition, there are other factors that can also pose risks to children, such as allergies, eczema caused by allergens, or hereditary problems.
During the childhood, boys have higher risks of asthma than girls. However, this tendency is reversed when they enter the adulthood period. According to researchers’ hypothesis, the size of male’s airway is relatively smaller than that of female, which may cause this difference between boys and girls. And once it’s infected through viruses, the smaller airways of male will cause wheezing to happen more often.
Actually, all asthma patients almost suffer from allergies. And more than 25% of patients with allergic rhinitis can develop asthma. What’s more, antibodies in the blood can lead to allergic reactions, which further inflame airways. This may be a major cause of asthma. Indoor allergens can be easily formed or dispersed. Pet dander, animal proteins, house dust mites, fungi, cockroaches, all of these can be commonly found indoors. The trend to build energy-efficient houses can also escalate the exposure to asthma causes.
Cigarettes smoke is not only highly associated with the incidence of asthma, but also increases the rate of death that is caused by wheezing, respiratory infections and asthma. What’s worse, children whose mother smoke, adolescent who have already began to smoke or people who are often exposed to the second hand smoke all have higher risks of asthma.
Today, indoor air pollutants have become the main threats to human health problems. For example, molds, chemicals and toxic gases brought out by indoor air pollution often lead to allergic reactions and asthma symptoms. Actually, nitrogen oxide released by gas stoves is also a big cause of asthma. People who often use gas stoves to cook have higher risks of asthma symptoms, like wheezing, hay fever, breath difficulties and asthma attacks.
It’s has been shown that nitrogen oxide, sulfur dioxide, ozone, air pollution and cold temperatures can trigger asthma among certain people. If air pollutants are intensive, asthma symptoms will be aggravated. That’s why there are so many hospital admissions during certain times. Some destructive pollutants, such as ozone, often released by smog are able to cause coughing, short breath or chest pain. And smoggy weather condition can also release tons of sulfur dioxide into the air, which can constrict people’s airways and further cause asthma attacks.
Another important environmental factor to cause asthma is the weather changes. It’s known to all that cold temperatures of the air are able to cause airways constriction, congestion, secretions, or decrease mucociliary clearance. Besides, humidity plays an important role on certain population groups’ health.
Comparing to adults who are with normal body mass indexes (BMIs), obese adults whose BMIs range from 25 to 30 have 38% higher risks of asthma. Adults with the BMI of 30 or above have twice chances of asthma. Researchers say that people with non-allergic asthma are posed higher risks of asthma than people who have allergic asthma.
How you come to the world may have great impact on your sensitivities to asthma. Usually, babies who are born by Casarean sections may have about 20% higher risks of asthma prevalence than those who are born by vaginal birth. During Cesarean sections, the immune system modifying may become infected due to bacterial exposure. That’s why the way of birth can impact asthma incidences.
If pregnant women smoke, their babies are more likely to have lower pulmonary function after birth, which can also pose the risk of asthma. According to researches, premature birth can be a potential risk of developing asthma.
For those people who are often undergoing stress, they have more chances of asthma, which can be partially because stress often can induce asthma-related activities, like smoking. But researches have shown that stress is also able to modify immune system.
It has been shown that about 100 genes are associated with asthma. And 25 of them are linked to separate populations as of 2005. Genes related to asthma have an important role on inflammation and immune system management. Although there are no consistent researches to study the genetic asthma across all population groups, further investigations should be taken to explore the relations between asthma and complex interactions.
60% of asthma is shown to be hereditary, so mother and father may be responsible for the asthma of their children. According to the Centers for Diseases Control in the United States, if one of a child’s parents has asthma, the chance for him to have asthma can be increased 3 to 6 times higher than those whose parents don’t have asthma.
What’s more, genetics may interact with environmental conditions. For instance, the genetic trait CD14 can have a gene-environmental interaction when people are exposed to bacterial product endotoxin, which has great associations with asthma development.
Although researchers haven’t found the clear evidences about the relation between airway hyperrectivity and asthma, cold air or allergens can probably trigger airway hyperreactivity, which may cause airways inflammations. Some people may have higher risks of asthma; while some can’t have the chance of asthma even thought their airways are hyperreactive.
Atopy is a major reason of asthma. Atopy is a predisposition toward developing certain allergic hypersensitivity reactions, such as allergic rhinitis (hay fever), atopic dermatitis (eczema), allergic conjunctivitis.
Studies show that 40% to 50% of children having atopic dermatitis have the risks of asthma. And they are also more likely to have more persistent and severe asthma than other adults.