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Allergies and Viruses an Asthmatic's Worst Nightmare

Exposure and sensitivity raises risk of trips to hospital

FRIDAY, March 29, 2002 (HealthDayNews) -- A combination of allergies and exposure to allergens and common viruses can give people with asthma a ticket to the hospital.

A new study by British researchers reports that a significant number of patients admitted to U.K. hospitals were both sensitive to allergens and had been exposed to those allergens, along with viruses including the common cold.

The researchers say the findings, which appear in tomorrow's British Medical Journal, could help doctors counsel asthmatic patients in hopes of reducing readmissions.

"It's really patients with severe, difficult asthma, and in particular those who end up being admitted to hospital, that are a problem," says study co-investigator Dr. Adnan Custovic, an honorary consultant allergist at Wythenshawe Hospital in Manchester, U.K.

Asthma consumes enormous health-care resources, but roughly 90 percent of those requirement are due to about 10 percent of people with the condition, he says.

The study's findings were released a day after U.S. federal health officials announced that asthma rates in the United States may be leveling off or even declining after rising steadily since the 1980s.

The Centers for Disease Control and Prevention reported yesterday that there were 17.2 deaths from asthma for every 1 million people in 1999. Between 1995 and 1998, the death rate was between 20 and 22 per million.

In addition, the report said, the rate of hospitalizations from asthma rose from 15.7 for every 10,000 people in 1998 to 17.6 in 1999, which was actually down from hovering near 20 per 10,000 people over the 1980s and early 1990s. And the rate of emergency room visits fell slightly, from 75.1 per 10,000 people in 1998 to 73.3 per 10,000 a year later.

The agency also cautioned that the numbers may be skewed because the survey the agency used to collect asthma data was changed slightly in 1997. Still, the report said, "the downward trend in asthma hospitalizations and asthma mortality might indicate early successes by asthma intervention programs."

In the British study, Custovic and his colleagues set out to find factors linked to hospital admission in patients with asthma. While they suspected that allergies, exposure to allergens, and viruses might play a role, there was no clear data drawing a line between these factors and hospital admissions.

The researchers studied 61 people between the ages of 17 and 50 who were admitted to the hospital with acute asthma, and compared them to 58 people with stable asthma and 59 others admitted to the hospital for different reasons. Every person went through skin prick testing for common allergens, which include household dust mites, cat and dog allergens, and grasses and trees.

The researchers visited the home of each person to collect information about exposure to the various allergens in the skin prick test, and they also collected nasal swabs for information on viral exposure.

Custovic and his colleagues found that 66 percent of the people admitted with acute asthma were both sensitized and exposed to allergens, compared to 37 percent of those with stable asthma and 15 percent of the control group.

But Custovic notes that individually, the factors were not enough to cause a problem.

"But if you are allergic and exposed to the allergens that you're allergic to, that is what increases your risk," he says. "Then, if on top of that, you catch a cold, you're in serious trouble.

"If an asthmatic patient who is not allergic to cats has a cat, it doesn't really matter, but if the asthmatic patient is allergic to cats and has a cat, it matters -- and if that guy gets a cold, then it matters a lot," he says.

"If you have asthma, it may actually put you into the hospital," he warns.

The problem lies in the already-sensitive airways of an asthmatic patient, he explains. "What allergens do in allergic people is they probably increase the inflammatory process in the airways," making lungs more vulnerable to viral infections like the common cold.

Custovic says that doctors may want to take these factors into account when they work with people with asthma.

"If you have someone who's allergic to dogs and keeps a dog in their home, it's important to tell them to get rid of dogs," he says. "At the same time, it's very important not to tell people to get rid of their pets if they're not allergic."

Finally, he says it's crucial to develop new therapies against what are often considered trivial viral infections, such as the common cold.

Dr. Martin Chapman, an adjunct professor of microbiology and medicine at the University of Virginia's Asthma and Allergic Diseases Center in Charlottesville, says that previous studies have linked admissions in children to the start of the school year, when kids are exposed to multiple viruses. Another study linked viral exposure in children to wheezing, which is often a precursor to asthma.

"The factors that control admissions with asthma may be allergens, may be viruses, and there may be 'synergies,' as they say in this paper, between the two," says Chapman.

But he says that mechanisms behind how allergens and viruses are linked to asthma flare-ups aren't well described.

Chapman adds that the respiratory response among asthmatics can vary depending upon which allergen they are exposed to.

The British researchers now plan to follow up with a similar study in children, along with intervention trials to determine if advising people with these risk factors can prevent readmission to the hospital.

What To Do

Just in time for the season for sneezin' – here's a spring allergy and asthma survival guide from the American Academy of Allergy, Asthma and Immunology

The National Institute of Allergy and Infectious Diseases provides further information on asthma and allergies.

SOURCES: Adnan Custovic, M.Sc., M.D., Ph.D., National Asthma Campaign Senior Clinical Research Fellow, reader in respiratory medicine and allergy, honorary consultant allergist, North West Lung Centre, Wythenshawe Hospital, Manchester, U.K.; Martin D. Chapman, M.D., adjunct professor, departments of medicine and microbiology, University of Virginia, member, UVA Asthma and Allergic Diseases Center, Charlottesville, Va.; Centers for Disease Control and Prevention report, Surveillance for Asthma -- United States, 1980-1999; March 30, 2002, British Medical Journal
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