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Whats Behind the Increase in Asthma?

June 10, 2008 - 7:30am
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What’s Behind the Increase in Asthma?

Image for increased asthma article For 6-year-old Sydney W., the winters in New England can be long. With the cold weather setting off her asthma, she sometimes spends recess inside while the other kids go out to play. Sydney may be the only child in her classroom with such severe asthma, but her situation is all too common in schools across the US.

The number of people with asthma in the US. has increased throughout the 1980s and 1990s and shows no sign of abating. In fact, according to the American Lung Association, in 2001, over 6 million American children and close to 14 million American adults suffered from asthma. And while Sydney’s asthma may only cause her to miss recess, many other children are more severely affected. Nationwide, children with asthma account for over 10 million school absence days every year. Asthma has become a huge public health issue, costing the US an estimated $14 billion per year.

What Is Asthma?

Asthma is a condition characterized by inflammation of the airways in your lungs. That inflammation is similar to the redness and swelling seen when you cut your skin, but in asthma it occurs inside the body. As the inflammation worsens, your airways become narrower and less air passes through to your lungs. It’s kind of like a clogged garden hose that only allows a trickle of water through, but in this case, it’s air that can’t get through. The inflammation also makes your airways more sensitive to irritation, so they tend to spasm and constrict more easily.

Symptoms of asthma may range from difficulty breathing to coughing, wheezing, or chest tightness and chest pain.

“It’s hard to get a deep breath,” explains Risha Nathan, a 24-year-old who was first diagnosed with asthma at age 11. “It’s also hard to get a breath out.”

For many people, their asthma has certain triggers. For Sydney, it’s cold weather. For Nathan, exercise causes symptoms to appear. Other common triggers include pollutants like tobacco smoke and smog, or allergens like dust mites, cockroaches, or cat dander. Catching a cold or a viral infection may also induce asthma attacks in many people. For some people, stress or certain medications such as aspirin may spark problems.

Why Is the Rate of Asthma Increasing?

Why more and more people seem to be suffering from asthma is not well understood. Some doctors blame the increase on what is sometimes called the “hygiene hypothesis.” This hypothesis suggests that because personal and public hygiene have improved in recent years, children suffer from fewer infectious diseases during early childhood. As the immune system develops, our bodies respond to allergens and pollutants rather than bacteria and viruses. The result is an immune system permanently biased toward allergic responses. As a result prevalence of asthma is increased. Particularly in people who have family histories of asthma and allergies.

Another hypothesis which has some scientific support but which remains unproven, is that if mothers’ lack Vitamin D (from sunlight or vitamin supplementation) during pregnancy, their children have a higher risk of developing childhood asthma by 3-5 years of age. Studies are currently underway to determine whether effective vitamin supplementation during pregnancy can reduce asthma risk.

It is unlikely that one factor explains the increase in asthma. Air pollution associated with very small particles (such as those from automobile and diesel exhaust – as well as indoor smoking) is very likely to be an important cause. Even when they originate outdoors, small particles are found in relatively high concentrations indoors – in homes and schools. Indoor molds, microorganisms whose growth is promoted by water leaks, poorly ventilated bathrooms, and other causes of damp environments, may also cause asthma in susceptible children.

How Is Asthma Treated?

Doctors treat asthma as a chronic (lasting over a long period of time) disease. Like hypertension or diabetes, the underlying condition is always present, even when a patient is not experiencing symptoms. Treatment for asthma is divided into two parts: removing asthma “triggers” from the environment to reduce the likelihood of symptoms, and treating those symptoms with a variety of drugs.

The National Heart, Lung, and Blood Institute (NHLBI) recommends quick-relief medications along with long-term anti-inflammatory treatments for most people with asthma. Quick-relief medications, such as albuterol inhalers, open up the airways quickly, but are short-acting and do not reduce the inflammation that persists long after an acute attack. Some long-term control medications, such as corticosteroid inhalers, reduce the underlying inflammation responsible for prolonged and recurring symptoms. Other long-acting medications (eg, salmeterol) do not have an effect on inflammation, and for maximum safety and benefit, must be combined with an inhaled corticosteroid.

For patients who experience asthma symptoms more than twice a week during the day, or more than twice a month at night, the NHLBI recommends taking long-term anti-inflammatory medications every day whether they have symptoms or not. Once patients improve, their doctor may allow them to reduce their level of medication.

What Else Can I Do?

Medications are only one approach to controlling asthma. You may also reduce your asthma symptoms by reducing your exposure to asthma triggers. Recent recommendations have put even greater emphasis on reducing trigger exposure. According to the Environmental Protection Agency, the most important of these triggers are:

  • Environmental tobacco smoke, sometimes called “secondhand smoke”
  • Dust mites
  • Mold
  • Cockroach and rodent (mouse and rat) droppings
  • Cat and dog allergens (from saliva, skin, and hair)
  • Nitrogen dioxides—from home heating, especially unvented heaters such as gas fireplaces

General recommendations for avoiding asthma triggers include:

  • Keep pets, food, and smoke out of your bedroom.
  • Cover your mattress and pillow with a dust-proof cover.
  • Wash sheets, blankets, and pillows weekly in hot water (>130ºF).
  • Try to have someone else vacuum for you or wear a dust mask while vacuuming. If possible, use a vacuum cleaner with high efficiency (HEPA) filters, which may reduce the amount of dust recirculated into the air by the vacuuming process.
  • Avoid strong odors, perfumes, paints, and smoke.
  • Get a flu shot every year.

If you are considering moving to a new city, be sure to check the Asthma and Allergy Foundation of America’s “Asthma Capital” list. The foundation ranks US cities on factors related to asthma: air pollution, pollen, smoke-free laws, accessibility of health care, and asthma-related statistics. If you have a choice, you might consider a city which receives a good ranking on the foundations’s list; it won’t guarantee freedom from asthma, but it may help. If you are not considering a move, the foundation recommends that you “Improve, don’t move!” You can work with others in your community to lobby for smoke-free indoors and reduced outdoor air pollution in your own environment.

Awareness of workplace exposures to industrial compounds known to cause lung disorders could also reduce asthma attacks for some employees. Many persons with asthma do not realize that workplace exposures can be responsible for some of the symptoms. The good news is that public health organizations are trying to reduce asthma triggers in our environment. Efforts to reduce chemicals in the air like nitrogen oxides and wood or tobacco smoke may potentially help many people with asthma.

Asthma is a chronic disease with symptoms that can vary throughout your lifetime. Encountering a new trigger, getting sick, or even changing an exercise routine may set off symptoms in someone who was previously doing well. Like other chronic diseases, the best way to manage asthma is to learn about your condition, communicate with your physician, and enlist support from family and friends.


American Lung Association

Asthma and Allergy Foundation of America

Asthma Program, U.S. Environmental Protection Agency

National Heart, Lung, and Blood Institute


Allergy Asthma Information Association

The Canadian Lung Association


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Expert panel report 2: guidelines for the diagnosis and management of asthma. National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf. Accessed May 20, 2003.

Facts about asthma: controlling your asthma. National Heart, Lung, and Blood Institute website.
Available at: http://www.nhlbi.nih.gov/health/public/lung/asthma/asth_fs.pdf. Accessed May 20, 2003.

Graham LM. All I need is the air that I breath: outdoor air quality and asthma. Paediatr Respir Rev. 2004;5 Suppl A:S59-64.

Lemanske RF Jr, Busse WW. Asthma. J Allergy Clin Immunol. 2003 Feb;111(2 Suppl):S502-19.

Litonjua AA, Weiss ST. Is vitamin D deficiency to blame for the asthma epidemic? J Allergy Clin Immunol. 2007 Nov;120(5):1031-5.

Mannino DM, Homa DM, Akinbami LJ, et al. Surveillance for asthma—United States, 1980-1999. MMWR. 2002;51:SS-1-6.

Trends in asthma morbidity and mortality. Epidemiology and statistics unit research and scientific affairs. March 2003. American Lung Association website. Available at: http://www.lungusa.org/data/asthma/asthma1.pdf. Accessed May 19, 2003.

Wood RA. Pediatric asthma. JAMA. 2002 Aug 14;288(6):745-7.

Last reviewed March 2008 by Lawrence Frisch, MD, MPH

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.



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