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More Americans being diagnosed with asthma

Doctors have theories why

POSTED: February 23, 2009 12:30 a.m.
SCOTT ROGERS/The Times

Nurse Supervisor Dena Free, right, of Allergy and Asthma Clinic of Northeast Georgia, explains to patient Roxanne Smith how to take a pulmonary function test Friday morning. The incidence of asthma in the United States continues to go up, yet researchers still don't know why.

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Researchers are still trying to figure out why there is such a high prevalence of asthma in the United States, where 10 percent of all children have been diagnosed with the condition.

In part, it may just be a matter of labeling.

"I do think we do a better job diagnosing it," said Dr. Michael Maloney of the Allergy and Asthma Clinic of Northeast Georgia. "In the old days, kids were sometimes diagnosed with ‘recurrent bronchitis’ or ‘reactive airways.’ Doctors kind of shied away from the term ‘asthma’ because sometimes it affected people’s insurance coverage."

But doctors aren’t simply renaming something that’s always been around. "I do think the prevalence has increased as well," said Maloney. "There are all kinds of theories about it, and I don’t think they’re ever going to come up with a single reason."

Some of the theories may seem a little bizarre. Recent studies have linked asthma rates to overuse of household cleaning sprays, lack of vitamin D and giving children Tylenol instead of aspirin.

But by far the most popular theory is the "hygiene hypothesis," which attempts to explain why people have more allergies (and thus, more allergic asthma) than they used to. A growing number of scientists think that growing up in an almost sterile environment doesn’t give the child’s immune system a chance to properly develop.

Asthma is rare in Third World countries, and it’s also uncommon in developed nations among children who grow up on farms, spending a lot of time outdoors and around animals.

"The hygiene hypothesis is controversial, but I do believe our kids are too ‘clean,’" said Dr. Ronald Beebe at Allergy and Asthma Associates of Gainesville. "We don’t have the childhood diseases we used to get, so the immune system gets ‘lazy.’ It starts making antibodies to things it’s not supposed to, like cats and carpets."

Beebe said about 85 percent of people with asthma have allergies. The rest experience asthma attacks triggered by non-allergic factors such as cold air and exercise.

Regardless of the cause, the mechanism of an attack is the same. The muscles of the airways go into a spasm and constrict. The inside of the airway swells up and becomes inflamed. This in turn causes excessive production of mucus.

The result, for the patient, is wheezing, coughing, shortness of breath and chest tightness.

Taking a daily maintenance medication can prevent these symptoms from occurring. If an attack does happen, it’s treated with a "rescue" medicine, a bronchodilator such as albuterol.

But when asthma is severe and poorly controlled, this medicine may fail to relax the airways.

"I’ve had patients end up in the ICU on a ventilator," said Dr. Ann-Marie Brooks, medical director of the Asthma Center at Children’s Healthcare of Atlanta.

Death from asthma is far less common than it used to be, but the condition still kills as many as 5,000 Americans a year. Brooks said patients need to take it seriously and keep up with their treatment regimen.

"In Augusta, four children died of asthma over the past year, and none of them were being followed regularly by a physician," she said.

One of the most vexing questions for doctors is why African Americans are much more likely to die of asthma. The easy explanation would be that they’re not getting preventive treatment, but the numbers are the same even among those with access to health care.

"Studies show that African Americans are at higher risk regardless of their socioeconomic status," said Brooks.

Maloney has observed this in his practice. "In general, asthma in blacks is more difficult to control," he said. "There’s no question genetics is involved."

Researchers are on a quest now to unravel the genetics of allergies and asthma. Dr. Andy Nish of the Allergy and Asthma Care Center in Gainesville said about 40 percent of adults in the U.S. have allergies, and they’re passing the trait along to their offspring.

"We do see families where all the children are affected and often one or both parents," he said.

Maloney said if neither parent has allergies, a child’s chances of having asthma are about 10 percent. "If they have one allergic parent, it’s 40 percent, and if both parents are allergic, it’s 80 percent," he said.

But even if scientists know a person’s DNA map, they can’t always predict whether that person will develop allergies.

"The genetics of asthma is very complicated," said Beebe. "It’s not a single gene. I had two patients who were identical twins. One was extremely allergic; the other had no allergies."

It appears that some people may be born with a tendency toward asthma, but something else has to happen before they begin having symptoms of the disease.

For example, it’s well known that obese people are more likely to have asthma. Being overweight doesn’t cause asthma, but it can make the symptoms worse.

Brooks said one reason is biomechanical. "The extra weight pressing against the chest wall can make it harder to breathe," she said.

Brooks said overweight children also tend to have unhealthy diets, eating things that may cause their airways to swell.

"There’s a growing belief that too much fats and processed foods may contribute to inflammation throughout the body," she said.

But there is no specific anti-asthma diet. Brooks said what’s most helpful is to eat lots of fruits and vegetables. And she said it’s a myth that asthmatic children should avoid milk because it’s "mucus-producing."

"There is no need to take your child off dairy unless they have a known milk allergy," she said.

Years ago, doctors also warned asthmatic patients not to exert themselves because it might trigger an attack. Now, they give the opposite advice. It’s true that exercise can precipitate an attack, but in the long run it helps strengthen the lungs and breathing muscles.

Some of the world’s greatest athletes, such as Olympic track star Jackie Joyner-Kersee, suffer from asthma.

"In my practice, I have to use significantly less medicine with patients who exercise," said Maloney.

But athletes with asthma succeed only when they follow their treatment protocol religiously. This usually means using their maintenance inhaler twice a day to prevent the airways from getting inflamed.

"This is a controllable disease," said Nish. "We’ve got great treatments now, and people can live normal lives."

Patient compliance can be an issue, however. "Asthma is an episodic disease," said Brooks. "For a long period of time, you may not have problems and you think you’re doing OK. That’s when people tend to stop taking their daily medication."

Other patients have the motivation to stick with the treatment, but they may not have the money.

"Asthma medications are incredibly expensive," said Brooks. "Few, if any, come in generic form."

With more people losing their jobs and health insurance, doctors worry that patients may try to go without their inhalers and end up needing treatment for a severe attack.

Asthma is already the top reason for hospitalization among children.

Mamie Coker, health services coordinator for Hall County Schools, said asthmatic kids also have a higher rate of absenteeism from school.

Coker said 1,335 students throughout the Hall system are identified on their health information forms as having asthma, but she suspects the actual number is much higher.

"In most cases their asthma is well-controlled with medication," she said. "If we find out that a student has asthma and they have no insurance, we try to get them into a program such as PeachCare or Medicaid so they can be under a doctor’s care."



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