- The Washington Times - Sunday, August 13, 2000

Look around a classroom. There is a good chance more than a few of the children have asthma. A couple more may be diagnosed soon.
More children than ever are asthmatic: In 1994, the National Institute of Allergy and Infectious Disease (NIAID) estimated that 14.6 million people had the respiratory disease; by 1998, the most recent year for which numbers are available, that number had risen to 17 million.
More than 5 million asthma sufferers are children younger than 18. Among children younger than 4, the condition has increased by 160 percent since 1980.
Still, doctors cannot pinpoint why so many people are suffering from asthma, a chronic condition that causes constriction of the lungs' bronchial tubes. With that constriction, air cannot get into or out of the lungs easily, and that causes wheezing, coughing and difficulty breathing.
"There is a fundamental piece of information we wish we had data for," says Dr. Marshall Plaut, chief of the allergic mechanism section at NIAID. "It is clear asthma is on the increase, but we don't know for sure why."
Doctors have many theories, though. Among the most prevalent: more pollution, better diagnosis, the rise in obesity and the "hygiene hypothesis." That last theory says that Americans with a plethora of vacuums and antibacterial products are desensitizing infants' immune systems.
Dr. Plaut is most skeptical about the pollution connection.
"Over the last 20 years, pollution levels have fallen, and asthma rates have risen," he says.
In fact, the indoor environment may be as much to blame as outdoor pollution, says Dr. Gail Shapiro, a Seattle allergist and president-elect of the American Academy of Allergy, Asthma and Immunology. The American lifestyle with television, computers and video games means people are spending more time indoors, where the air is full of pet hair, dust mites and mold, Dr. Shapiro says.
When a person is diagnosed with asthma, taking care of the environmental factors is as important as taking medication, she says. That could include everything from covering bedding (where dust mites abound) with special covers to ridding the bedroom of stuffed animals (which accumulate dust), says Dr. Richard Rosenthal, allergy section chief at Inova Fairfax Hospital.
"The first part of the treatment plan is avoidance," Dr. Rosenthal says. "If you are allergic to dust mites, you probably have them."
Dust mites are microscopic living creatures that live off sloughed-off human skin and produce droppings that are highly allergenic. Carpets, blinds and bedding are common places where they are found. Dr. Shapiro recommends replacing wall-to-wall carpeting with washable rugs and washing bedding in very hot water to cut down on mites.
If a pet proves to be contributing to the condition, Dr. Rosenthal advises keeping the animal out of the bedroom and having a different family member groom the pet. Though telling patients to get rid of a dog or cat certainly would cut down on the asthma trigger, Dr. Rosenthal says he knows that is not always practical advice.
"Most people will not get rid of pets," he says. "They are important family members."
Dr. Rosenthal also advises using a central air-filtration system and running a humidifier in the winter, as dry air can irritate airways, provoking an attack.
Indoor irritants particularly are a factor in the inner city, where cockroaches big asthma triggers are found more readily, Dr. Plaut says.
Black children in inner cities are three times more likely to be hospitalized with an asthma attack and four to six times more likely to die from an asthma attack than white children, Dr. Plaut says.
Those numbers are blamed partly on inadequate health care. A recent study of 392 asthmatic inner-city children by doctors at Johns Hopkins and Howard universities showed that a majority relied on emergency care to manage their condition and few children took preventive medications on an appropriate, regular basis.
Obesity is another lifestyle factor that is contributing to the rise in asthma, some researchers say. While asthma cases have more than doubled since 1980, the proportion of obese adults has increased by 10 percent and the number of extremely overweight children has almost doubled, according to researchers at Harvard Medical School.
A 1999 Harvard study of 16,862 children ages 9 to 14 found that those who were the most overweight were two to three times more likely to have asthma than the least overweight subjects. A study completed this year at the University of Oklahoma tracked more than 12,000 men and found that their body-mass index (BMI) was a strong predictor of asthma.
Dr. Carlos Camargo, the lead Harvard researcher, says it is still unclear how obesity influences asthma risk, but the sedentary lifestyle some children lead may contribute to both asthma and obesity. When one is sitting (such as while watching television), breathing is shallow, which may increase bronchial reactivity and airway irritation, he says.
Says Dr. Plaut: "People in the city and in the suburbs are exercising less frequently. They are watching TV and are not outside as much. That may affect the function of their lungs. We find some of the lowest rates of asthma in the world in rural New Guinea, where people are not indoors and not exposed to a sedentary lifestyle."
The "hygiene hypothesis" is one of the most intriguing theories but also one of the most controversial, Dr. Plaut says. It basically states that the environment, particularly in early childhood, is too clean.
In a house free of dust, infants and small children are not able to build up exposure to allergy-producing substances, say scientists at Denver's National Jewish Medical and Research Center.
Dust contains bacteria, and when bacteria die, their cells release a substance called endotoxin. When a child's immune system detects endotoxin, it responds by making cytokines, proteins that make the body less sensitive to substances such as mites, animal dander and pollen, says Dr. Andy Liu, an asthma specialist at the National Jewish Medical and Research Center and author of a recent study that appeared in the British medical journal Lancet in May.
Dr. Liu says exposure to endotoxin may play a role in preventing allergies after infancy. However, if a child already has asthma or allergies, the presence of endotoxin may exacerbate the disease.
Dr. Liu studied the homes of 61 infants ages 9 to 24 months who had experienced at least three episodes of wheezing, which can be an early indicator of asthma. The infants were tested for sensitivity to dust mites, cats, dogs, cockroaches, mice, milk, egg and soy.
Of the 61 infants, 51 tested negative to those substances. The concentration of endotoxin was the highest in the homes of children with negative allergen skin tests.
"Children who were allergen-sensitive had less environmental endotoxin in their homes," Dr. Liu says. "The amount of endotoxin seems to correlate with immune system development. This may be an important clue in the development of effective asthma prevention."
Scientists at the National Institutes of Health's National Institute of Environmental Health Sciences are two years into an eight-year study that will further investigate the hygiene hypothesis.
The NIEHS researchers are studying 500 newborns at high risk for asthma to determine the best way to reduce allergens (such as covering mattresses with dust-mite-proof coverings, steaming carpets and trapping roaches. Half of the newborns will be raised in homes with allergen-free zones; the others will be part of a control group.
In a separate study, NIEHS researchers also are looking at the genetic link in asthma.
"Asthma is somewhat linked to genetics," Dr. Shapiro says, "but it is not a simple pattern. Response to medication also shows a genetic pattern."
Rick Clark of Manassas suspects there is a genetic link. The 17-year-old relies on a steroid inhaler to manage his asthma. Both his brother and his father have the condition, too.
"It bothers me every day," says Rick, whose asthma often flares up with exercise and physical activity. "It is hard to breathe deeply. I've gotten it pretty well under control, though."
While all the research may uncover new treatments for the disease, it is unlikely to provide one absolute reason for the rise in cases, some experts say.
"I think it is a combination of these things," Dr. Shapiro says, "and the longer the list, the more we have the feeling we don't know at all why it is on the rise."

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