Stomach Germ May Protect Against Asthma

Disappearance of H. pylori could leave kids more susceptible to the disease, study says

TUESDAY, July 15, 2008 (HealthDay News) -- A stomach bacterium called Helicobacter pylori may reduce a child's risk of developing asthma by as much as 50 percent, a new study suggests.

H. pylori has been present in the human stomach probably since humans were humans. However, the germ began disappearing over the course of the 20th century with the introduction of antibiotics and cleaner water and homes, perhaps making children more susceptible to asthma, the study authors suggested.

"In our study we asked the question, is there any relationship between having H. pylori in the stomach and having asthma and other allergic disorders," said lead researcher Dr. Martin J. Blaser, the Frederick H. King Professor of Internal Medicine and chairman of the department of medicine at the New York University Langone Medical Center in New York City.

"We found a strong inverse association between H. pylori and childhood asthma, childhood hay fever and childhood allergies," added Blaser, who's also a professor of microbiology and has studied H. pylori for more than two decades.

Blaser thinks that H. pylori may protect the body against asthma. "When children have H. pylori in their stomach, their immune system is different than if they don't have H. pylori," he said.

H. pylori has been disappearing especially since World War II, which is when the incidence of asthma began increasing, Blaser said.

For the study, Blaser and his colleague Yu Chen, an assistant professor of epidemiology, collected data on 7,412 children who participated in the 1999 to 2000 National Health and Nutrition Examination Survey IV, conducted by the National Center for Health Statistics.

Among children in the survey, just 5.4 percent born in the 1990s tested positive for H. pylori. In addition, 11.3 percent of the children under 10 had taken antibiotics in the month before the survey.

Blaser and Chen found that among children 3 to 13 years of age, those who carried the stomach bug were 59 percent less likely to develop asthma than children without H. pylori. These children were also 40 percent less likely to suffer from hay fever and other allergies, such as eczema or rash.

Among children aged 3 to 19, the researchers found that those who harbored H. pylori reduced their risk of asthma by 25 percent.

"This is a new way of saying who's at risk for asthma and who's not," Blaser said. "You can't mess with Mother Nature. This bacterium that has been present forever in the human stomach has been disappearing, and that has consequences."

Some of the consequences are good, however, Blaser noted. These include the decline of ulcers and decreases in stomach cancer among adults, he said. "But these are diseases of old age," he said. "It is possible that H. pylori may be protective of children, but bad for old people."

The study findings were published online July 15 in The Journal of Infectious Diseases.

Dr. Clifford Bassett, medical director of Allergy and Asthma Care of New York in New York City, thinks the findings open a new window on doctors' understanding of asthma and allergies.

"It appears this will add to our knowledge and research looking at incidence and prevalence of asthma and allergic diseases in children and adults in an increasingly sanitized world," he said. "The relevance of H. pylori as a potential risk in asthma is quite thought-provoking by any means."

More information

For more on asthma, visit the U.S. National Institutes of Health.

SOURCES: Martin J. Blaser, M.D., the Frederick H. King Professor of Internal Medicine, chair, department of medicine, and professor, microbiology, New York University Langone Medical Center, New York City; Clifford Bassett, M.D., fellow, American Academy of Allergy, Asthma and Immunology, and medical director, Allergy and Asthma Care of New York, New York City; July 15, 2008, The Journal of Infectious Diseases, online
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