Free asthma screenings are scheduled to be held at 250 locations across the United States as part of National Asthma and Allergy Awareness Month. The American College of Allergy, Asthma & Immunology sponsors the annual effort, and this year the emphasis is on helping those already diagnosed with asthma to get it under control as best they can.

In recent months, the National Heart, Lung, and Blood Institute (NHLBI) put out new guidelines highlighting the importance of asthma control, including daily monitoring and proper medication use to treat symptoms and prevent severe attacks from occurring. This came in light of research showing that many people with asthma are suffering more than they need to from the disease.

"The government guidelines emphasize that undiagnosed or inadequately treated asthma worsens the severity of the disease," allergist John Winder, chairman of the Nationwide Asthma Screening Program, said in a prepared statement. "The screening program gives patients who are still having breathing problems a chance to meet with an allergist, discuss their symptoms and learn how to feel better."

More than 22 million Americans, including 6.5 million children, have asthma -- a chronic inflammation of the airways in the lungs. Asthma attacks, which claim nearly 4,000 lives a year, are often triggered by allergens -- these include pollen, dust, animal dander, certain drugs and food additives -- lung infections, or even physical exertion. While the disease's exact cause remains unknown, many treatments are available to keep it in check.

"An asthma 'attack' isn't the only sign of trouble. A cough that bothers you at night, shortness of breath, colds that go to your chest -- these can all be symptoms of asthma. But few people recognize them or that they are a sign of under-treated disease," Winder said. "No one with asthma should have to suffer. Anyone who is experiencing breathing problems or making compromises to live with their condition should attend a free screening and find out how to take control."

The screenings will be overseen by allergists, who are asthma specialists, and done in coordination with local doctors and allied health professionals. During a screening, participants will answer several questions about their breathing issues, take a lung function test that involves blowing into a tube, and meet with an allergist to determine whether a more thorough exam and diagnosis is needed.

The program has screened more than 108,000 people over the years, and more than half of those were referred for further diagnosis.

A list of free asthma screening locations and dates, online versions of the breathing questionnaires, and more information on treating and controlling asthma are on the ACAAI Web site at www.acaai.org.

More information

The National Heart, Lung, and Blood Institute has more information about controlling and treating asthma.

"We have demonstrated significant differences in the changes in respiratory function that occur with asthmatic bronchoconstriction in relation to obesity," principal investigator Dr. D. Robin Taylor, of the University of Otago in New Zealand, said in a prepared statement.

The study also found that simple spirometry couldn't determine the level of pulmonary dysfunction in obese people with asthma.

The findings were published in the first issue for May of the American Journal of Respiratory and Critical Care Medicine. It's the first prospective study to find a significant comparative difference between obese and non-obese people in how the lungs and airways respond to a simulated asthma attack.

The researchers said it establishes a direct link between obesity and the development of dynamic hyperinflation -- air breathed into the lungs can't be expelled. This often occurs with acute asthma, but is more frequent in obese people.

The study included 30 asthmatic women who were divided into three groups based on their BMI: normal weight, overweight and obese. All the women breathed nebulized methacholine to induce an asthma-like attack and were then assessed for changes in lung function, including functional residual capacity (FRC -- how much air remained in the lungs after exhalation) and inspiratory capacity (IC -- how much air could be inhaled on the next breath).

"After the methacholine challenge, the amount of bronchoconstriction was identical for each of the three groups, but the changes in FRC and IC were greatest in the obese group. This indicated to us that greater dynamic hyperinflation was occurring among obese individuals," Taylor said.

The greater a woman's BMI, the higher her FRC and the lower her IC.

"This means that among women with greater BMI, an asthma-like episode has the potential to cause greater breathing difficulties than in non-obese women. The greater dynamic hyperinflation means that obese individuals lose the ability to inhale as deeply or exhale as fully as normal weight individuals," Taylor said.

The findings suggest fundamental differences in the way that obese people with asthma may experience shortness of breath.

"We know that asthma in obese subjects is more likely to persist and is more likely to be perceived to be severe. These individuals often require more treatment to achieve asthma control. Our study provides an insight into why this might be happening -- the same asthma trigger produces a greater effect in obese individuals," Taylor said.

More research is needed to "confirm that the differences in dynamic hyperinflation between obese and non-obese asthmatics are sufficient to explain the differences in symptoms between the two groups. Our study was not large enough to do this," Taylor said.

More information

The U.S. National Heart, Lung, and Blood Institute has more about asthma.

Researchers looked at asthma rates among children aged 4 to 5, and asthma-related hospital admissions for children up to age 15, in 42 service districts of New York City. Asthma is the leading cause of hospital admission among children aged 15 and younger in the city.

The researchers compared the medical data to information about the number of trees in each of the districts, along with sources of pollution, population density, and racial and ethnic composition.

Nine percent of the young children in the study had asthma, and the city had an average of 613 trees per square kilometer. Asthma rates decreased by almost one-quarter for every standard deviation increase in tree density, equivalent to 343 trees per square kilometer, the study found. This pattern held true even after the researchers factored in sources of pollution, socioeconomic status and population density.

However, there was no association between tree density and asthma-related admissions to hospital among older children.

The results don't mean that tree density in a neighborhood is directly related to asthma rates among children, said the researchers, who added that trees may help reduce asthma rates by encouraging children to play outdoors more or by improving air quality.

The study was published online in the Journal of Epidemiology and Community Health.

The researchers noted that New York City is planning to plant 1 million extra trees by 2017, which could provide an opportunity to study exactly what impact tree density may have on asthma.

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The American Lung Association has more about childhood asthma.

The Inner City Asthma Study Group researchers, who looked at 861 children, ages 5 to 12, with persistent asthma, said their findings raise questions about current air quality standards in the United States. They suggest that asthma management plans for inner-city children may need to include reduced exposure to air pollutants.

For two years, the researchers monitored the asthma symptoms of children living in low-income inner-city sections of Boston, New York City, Chicago, Dallas, Seattle and Tucson.

These youngsters had significantly decreased lung function following exposure to higher concentrations of air pollutants such as sulfur dioxide, airborne fine particles, and nitrogen dioxide. The study also found that higher nitrogen dioxide levels and higher levels of fine particles were associated with asthma-related school absences, and that higher nitrogen dioxide levels were associated with an increase in asthma symptoms.

Since motor vehicle exhaust is the main source of nitrogen dioxide, the findings suggest that car emissions may be causing respiratory problems among inner-city children with asthma, the researchers said.

The study, supported by the U.S. National Institutes of Health and Environmental Protection Agency, was published in The Journal of Allergy and Clinical Immunology.

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The Nemours Foundation has more about air pollution and asthma.

The genetic variation in CHI3L1 causes the gene to release high levels of a protein known as YKL-40, and high levels of this protein have been associated with an increased risk of asthma in past research. The current study found that high levels of YKL-40 in four different population groups were linked to the development of asthma in all four groups, suggesting that YKL-40 and CHI3L1 are likely at the root of some cases of asthma.

That means if scientists can block YKL-40, they could create a novel, potentially more effective treatment for people with asthma.

"While there won't be one silver bullet for all asthma, we can start to think about tailoring medications to get at the cause, rather than just alleviating asthma symptoms," said study author Carole Ober, a professor of human genetics at the University of Chicago. "These findings give us optimism that one day there will be better treatments, more targeted to the specific cause of asthma."

The findings were published online April 9 by the New England Journal of Medicine and were expected to be in the journal's April 17 print issue.

It's believed that YKL-40 was originally produced by the body as a defensive mechanism against harmful parasitic worms, called helminths, according to Dr. Burton Dickey, chairman of pulmonary medicine at M.D. Anderson Cancer Center in Houston. Dickey said that helminths contained a substance called chitin that is also found in fungi, crustaceans and in insects such as dust mites and cockroaches. YKL-40 is what's known as a chitinase-like protein, because it attaches itself to chitin, possibly alerting the body that chitins are present.

But, Dickey pointed out that in the developed world, chitin infections simply aren't an issue any longer, so now this defense mechanism may be reacting to chitin in harmless settings.

In November 2007, Yale researchers reported that people with severe asthma had higher levels of YKL-40. This finding led to the current study, which measured levels of YKL-40 in an isolated population called the Hutterites. The Hutterites settled their isolated religious community in South Dakota in 1874. They live communally, share the same food, have the same education and socioeconomic status. About 11 percent of Hutterites have asthma, and 12 percent have hyperactive airways.

Working with the Yale team, Ober found that the Hutterites with asthma or overactive airways had elevated levels of YKL-40. After searching their genetic code, Ober and her colleagues found that one tiny change in the CHI3L1 gene was slightly different in Hutterites with asthma. When the researchers compared these findings to three different groups of people from Chicago; Madison, Wisc.; and Freiberg, Germany, they found an association with changes in CHI3L1 and YKL-40 levels, and the development of asthma. Some children were too young to have developed asthma, but already showed higher levels of YKL-40 if they had the genetic change.

Ober said that not everyone with high levels of YKL-40 develops asthma, but that someone with the CHI3L1 change inherited from both parents "was twice as likely to develop asthma as someone who doesn't have it."

"YKL-40 seems to be involved in many different diseases in which inflammation is a component, and so it is likely to be an important component of the innate immune response, and treatments directed at YKL-40 may be helpful in all of these diseases," said Dr. William Cookson, co-author of an accompanying editorial and a professor of respiratory genetics at the National Heart and Lung Institute at Imperial College in London.

Dickey said the Yale team is currently working on an animal model that doesn't produce YKL-40 to see if the protein is important in other functions in the body.

"If the protein doesn't contribute importantly to any other biological process, it's likely just involved as a parasitic defense, and inhibiting it may not cause any problems, yet could provide substantial benefit [in terms of asthma treatment]," said Dickey.

More information

To learn more about the causes of asthma, visit the National Heart, Lung, and Blood Institute.