Asthma affects an estimated 20 million people in the United States and costs the nation billions of dollars in lost productivity and hospitalization costs. The Federal Government and pharmaceutical companies in turn spend billions of research dollars each year in an effort to better diagnose and treat asthma. Below is an overview of some of the recent medical developments in asthma research followed by links to some recent scientific and news articles about asthma.

Genetics of asthma

While it is known that genetics play an important role in the development of asthma, exactly which genes are involved is still a mystery. There is no evidence yet that just one gene causes asthma. More likely there are several genes that interact to increase the likelihood of developing asthma as long as certain environmental conditions are also encountered. For example, if you live in a bubble and are never exposed to any asthma triggers, you will probably never develop asthma even if you have all the right genes. Genetic techniques developed in the last 20 years have allowed scientists to analyze families with several asthma cases and determine which genes the asthmatics share that unaffected individuals do not. One of the candidate genes identified so far is called ADAM33 and is involved in lung and muscle cell development. This gene may cause the airways to constrict more than normal when they encounter asthma triggers. Several other genes have also been identified as possible candidates in asthma susceptibility. These include genes involved in immune system signaling, in tissue remodeling, and in the response to antioxidants

Asthma Diagnosis

Nitric oxide

While lung function tests using a spirometer are currently the most accurate way of diagnosing asthma, they are not perfect. Researchers are trying to find better ways to diagnose asthma and determine the appropriate levels of asthma medications to prescribe. One candidate is a test for exhaled nitric oxide, a natural gaseous chemical whose levels tend to increase in exhaled air with increasing asthma severity. The amount of exhaled nitric oxide even decreases with corticosteroid treatment as asthma symptoms improve. Research is currently underway to determine if nitric oxide is a better method for diagnosing and tracking asthma than spirometry tests. Initial results are promising, but the equipment is still very costly and the test still needs to prove its clinical relevancy.

Asthma treatments

Several groups of scientists have used mice as a model to study asthma in humans. One of these groups has identified a protein found in certain lung cells called NF-B as critical to the development of asthma (at least in mice). If this proves to be true in humans as well, it could provide an important therapeutic target since blocking it might prevent asthma from developing. This would be a huge breakthrough because all of the current medications for asthma are only designed to stop asthma attacks from happening. They only work after someone has already been diagnosed with asthma. A drug that targets a key step in the development of asthma could prevent asthma altogether. A lot of work remains, but it is likely that similar molecules critical to asthma development in humans will be discovered in the future.

Asthma risk factors

Exposure to allergens and irritants

While several studies suggest a link between young children who are exposed to certain allergens in the home and increased development of allergies to those substances, recent studies indicate that no such relationship exists between allergens in the home and childhood asthma. However, there are some things that a child can be exposed to which increase their risk of developing asthma. Exposure to tobacco smoke either in the womb or after birth is a major risk factor for developing asthma. In addition, results of several studies suggest that exposure to pesticides and wood smoke may also increase the risk of childhood asthma. It is not clear exactly how these irritants increase asthma risk but one theory holds that repeated exposure of infant lungs to irritants causes them to develop a hypersensitivity to chemicals so that upon exposure, they respond with greater inflammation.

Another factor that has received a lot of attention is airborne irritants from diesel fuel exhaust. Several studies indicate that exposure to diesel exhaust not only triggers asthma symptoms in those who are sensitive, it also increases the risk of developing asthma. Diesel exhaust contains at least 40 different types of particles that appear to cause the lungs to become inflamed, release mucus, and constrict the bronchioles, all the hallmarks of asthma. This increased risk may begin to explain why living in densely populated urban areas is a risk factor for developing asthma. Certain urban areas with high levels of diesel bus traffic, such as Harlem in New York City, have an extremely high incidence of asthma, especially in children. There are probably other airborne pollutants that increase relative asthma risk in urban areas but diesel exhaust is one of the best studied so far.

Why is asthma on the rise?

In the past 30 years, the number of people with asthma in the United States has more than doubled and much of this increase is in children and adolescents. So why is this happening? Researchers are trying desperately to figure it out. Many theories have been put forth attempting to explain the increase. One is that genetic factors are to blame. This is not likely to be the whole story because the increase in cases is too large and too rapid to be explained by inheritance alone. Another theory is that an increase in household allergens is causing more asthma cases. This is also unlikely to be a main cause because most evidence to date suggests very little relationship between these allergens and asthma development.

Another theory that attempts to explain the increase in asthma cases is sometimes called the “hygiene hypothesis.” The idea is that our increased use of cleaners, disinfectants, and antibiotic soaps has sanitized our living environment to the point where our immune systems have become “bored” and tend to overreact in the presence of allergens. However, this cannot account for the observation that asthma rates are also on the rise in far less sanitized places such as India. It also fails to explain why the increases are so large in the African American and Hispanic/Latino communities, as well as in urban areas within the United States.

Several theories have been advanced that may help explain the recent increase in asthma. More cars and trucks are on the road now than ever before, so higher levels of diesel exhaust, ozone, and other automobile pollutants may be responsible. Indoor chemicals such as those used in newer building materials and plastics may cause increased sensitivity to allergens. Exposure to other irritants like pesticides may also make asthma more likely to develop. The most likely explanation is that a combination of these factors and others we haven’t thought of yet are responsible for the increase in asthma. Unfortunately, the effects of all of these factors may be greatest during the critical period of lung development in the womb and just after birth; most chemicals and pesticides have never been studied in pregnant women or infants so their effects on these populations is unknown. Many studies are now underway to learn what factors are responsible for the recent steep increase in asthma cases and what we might be able to do to reduce their impact.

Links to recent asthma news and developments

Environmental Protection Agency (EPA) asthma news.
http://www.epa.gov/asthma/news.html

Asthma news on Science Daily, a digest of recent science research news.
http://www.sciencedaily.com/news/health_medicine/asthma/

PubMed is a U.S. National Institutes of Health search engine that covers all research published in medical and bio-scientific journals.
http://www.ncbi.nlm.nih.gov/PubMed/

PubMed Central is the National Institutes of Health free digital archive of biomedical and life sciences journal literature.
http://www.pubmedcentral.nih.gov/

Medline Plus, a service of the NIH, has links to recent asthma news stories.
http://www.nlm.nih.gov/medlineplus/alphanews_a.html#asthma

The U.S. Food and Drug Administration Center for Biologics Evaluation and Research is the government agency charged with reviewing and approving applications for new drugs and medical devices and their website ahs information about recent developments in these areas.
http://www.fda.gov/Cber/index.html

Information about clinical trials

To find a clinical trial being conducted in your area, visit the Healia clinical trials search page.