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Ulcer-Causing Bacteria May Prevent Asthma

H. pylori might also protect against allergies, study says

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HealthDay Reporter

MONDAY, April 23, 2007 (HealthDay News) -- The bacteria responsible for many peptic ulcers, Helicobacter pylori, may not always act in a damaging way. Instead, new research suggests that the germs may actually protect against asthma and allergies.

Using data from almost 8,000 adults, researchers from New York University School of Medicine found that people infected with a particular strain of H. pylori had a 21 percent decreased risk of having asthma and a 23 percent decreased risk of allergies compared to people without the bug. What's more, the researchers found that when the infection with H. pylori occurred before the age of 15, the odds of having asthma were reduced by 37 percent, and the odds of allergies were reduced by 45 percent.

"Helicobacter pylori has been found to be strongly associated with ulcer disease and stomach cancer, and there's a widespread belief that this organism is a pathogen," said the study's co-author, Dr. Martin Blaser, chairman of the department of medicine and a professor of microbiology at NYU.

But, about 10 years ago, Blaser said, he and other researchers looked at H. pylori's association with another common digestive disorder, gastroesophageal reflux disease (GERD), and found that there was an inverse relationship between having H. pylori and having GERD. That finding "raised the idea that helicobacter might be protective. It's bad for the stomach, but good for the esophagus."

As many as one in five people under age 40 is infected with H. pylori, according to the National Institute for Diabetes and Digestive and Kidney Disorders. Yet, not everyone who's infected develops an ulcer.

Because H. pylori appeared to be protective against GERD, and previous research had linked GERD and asthma, Blaser and his colleagues wondered if H. pylori might protect against asthma as well.

To evaluate this theory, Blaser and his colleague, Yu Chen, culled data from the Third National Health and Nutrition Examination Survey about asthma and allergy history for 7,663 adults. The researchers also assessed whether the study volunteers had evidence of strains of H. pylori called CAG positive or CAG negative in their blood.

"What we found was that if people ever had a history of asthma, there was an inverse association with CAG positive helicobacter," said Blaser. And, he added, when the researchers broke the data down by age, they found an even more "striking result."

"We have evidence that helicobacter used to be ubiquitous in the environment, and it used to be acquired in childhood," said Blaser. "Now, we have a generation of children growing up with helicobacter in their stomachs to help regulate immunity and maybe protect against asthma and allergy. This could be an unintended consequence of all the antibiotics used in children.

"It's possible helicobacter is protecting against asthma to some degree, and, as it disappears, we're losing that layer of protection, which may explain why asthma, especially childhood asthma, is rising," he said.

Results of the study are published in the April 23 issue of the Archives of Internal Medicine.

Not everyone is convinced that helicobacter is at the root of asthma, however.

"This study doesn't sway me in any way in how I treat my asthma patients," said Dr. Jane Krasnick, chief of allergy and immunology at St. John Macomb Hospital in Warren, Mich.

Krasnick said the study has some limitations, such as the asthma was self-reported, not confirmed by lung function tests or doctors. Additionally, she said, there was no mention of the severity of asthma or details on the types of medications the study volunteers were taking. Such factors could affect the study findings, she pointed out.

Still, Krasnick said, "Medicine can be like a big jigsaw puzzle, and this may be a piece of that puzzle. Maybe right now, you noticed this piece has fallen under a chair, and you wonder if it's important, so you go back to get that piece and keep it in a drawer in case you need it later."

Blaser said additional research needs to be done to confirm the association and then to figure out what to do with this knowledge. Right now, he said, many physicians think all H. pylori infections need to be treated, even those not causing ulcer symptoms.

But, he said, "Helicobacter is part of the natural human body. It's quite ancient in humans and has been living in the human stomach for a very long time."

More information

You can read more about H. pylori and its relationship to peptic ulcers at the National Institute of Diabetes and Digestive and Kidney Diseases.

SOURCES: Martin Blaser, M.D., the Frederick H. King professor of internal medicine, chairman of the department of medicine, and professor of microbiology, New York University School of Medicine, New York City; Jane Krasnick, M.D., chief, allergy and immunology, St. John Macomb Hospital, Warren, Mich.; April 23, 2007, Archives of Internal Medicine

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