A new study links a stomach microbe to asthma prevention

April 23, 2007

NEW YORK, April 23, 2007 -- The stomach bacterium Helicobacter pylori, which causes stomach cancer and peptic ulcers, may not be all bad. According to a new study, it may help protect kids from asthma.

The study, based on an analysis of a health survey of 7,663 adults, showed that a virulent strain of H. pylori was especially associated with being asthma-free before the age of 15. People who carry the strain were 40 percent less likely to have had asthma at an early age than those who didn't carry the strain. The study also found that the microbe was associated with protection against ragweed and other allergies due to pollens and molds particularly among younger adults.

The study is published in the April 23, 2007, issue of Archives of Internal Medicine.

"Ultimately, the potentially protective properties of Helicobacter are consistent with one another," explains Martin J. Blaser, M.D., the Frederick H. King Professor of Internal Medicine, Chairman of the Department of Medicine, and Professor of Microbiology at NYU School of Medicine, who has been studying H. pylori for more than 20 years.

"These properties point toward a much more complex view of the organism--not just as ulcer-pathogen or cancer-pathogen, but as an organism that has its costs and benefits to us," says Dr. Blaser. "The relative costs and benefits clearly differ among individuals."

Dr. Blaser performed the study with Yu Chen, Ph.D., MPH, assistant professor in the Department of Environmental Medicine at NYU School of Medicine, a new faculty member with expertise in epidemiology.

H. pylori lives in the mucous layer lining the stomach where it persists for decades. It is acquired usually before the age of 10, and is transmitted mainly in families. Dr. Blaser's previous studies have confirmed the bacterium's link to stomach cancer and elucidated genes associated with its virulence, particularly a gene called cagA.

Over recent years, Dr. Blaser began to suspect that the organism, the dominant bacteria in the stomach, may play a role in human health as well as disease. This observation, he says, is consistent with a theory called the hygiene hypothesis. It suggests that exposure to microbial infections in early childhood prevents or diminishes the development of allergies and asthma.

Dr. Blaser has proposed that H. pylori may protect against diseases of the upper gastrointestinal tract, such as gastroesophageal reflux disease (GERD), which may lead to Barrett esophagus, a premalignant condition, and adenocarcinoma of the esophagus. All of these conditions have become more common in developed countries - esophageal cancer of this type is the fastest rising cancer in the United States - as H. pylori has become far less common due to improved sanitation and widespread use of antibiotics, says Dr. Blaser. (At the same time, the incidence of peptic ulcers and gastric cancer has declined in developed countries.)

Today, less than 10 percent of children carry the organism in industrialized countries, while some 90 percent of children are infected usually by age 5 in developing countries. "This bacterium has been the dominant organism in our stomach for tens of thousands of years, and it can't disappear from us without consequences," says Dr. Blaser. He says that a substantial body of work now shows that H. pylori helps protect against GERD and the conditions it leads to in the esophagus.

"The hypothesis that colonization of H. pylori, especially cagA strain, is protective of asthma risk needs to be tested by prospective studies. The findings from our study and others will collectively provide evidence," says Dr. Chen.

If the relationship between H. pylori and asthma is confirmed in other studies, which is always the yardstick of scientific validity, then it raises the question about whether "we should be trying to eliminate Helicobacter from children," says Dr. Blaser. "This is probably the first time in human history that we have children who are growing up without Helicobacter guiding their immune responses," he says. "By the repeated courses of antibiotics given to children, we are changing human microecology and we don't know what we are doing."

In the new study, Drs. Blaser and Chen evaluated whether H. pylori's protective effect against GERD could play a role in asthma, another condition sometimes associated with GERD. They used data from the Third National Health Nutrition Examination Survey (NHANES III), which was conducted from 1988 to 1994, and originally involved nearly 40,000 people. The survey included questions about a medical history of asthma, allergic rhinitis, and allergy symptoms. Nearly 8,000 of the participants were tested for antibodies to H. pylori and the cagA protein in their blood. This subgroup formed the basis of the study.

Drs. Blaser and Chen found no overall association between the presence of the cagA strain of H. pylori and current asthma status in the individuals they studied, but found an inverse association with ever having had asthma. Those with the virulent strain were 20 percent less likely to have ever had asthma compared with participants without H. pylori. In addition, the association differed quite strikingly by age of onset. It was strongest among participants who had the cagA strain of H. pylori and had had asthma before the age of 15. This result was statistically significant, meaning that the results were not likely due to chance. Those with the virulent strain were 40 percent less likely to have had asthma at a young age.

In another part of the study, they analyzed the results of allergy skin testing to six allergens, including ragweed, rye grass, and Russian thistle, among a subgroup of 2,386 adults who had the skin tests. They correlated the results with participants' H. pylori status and found the strongest association for these allergens among the younger people in the group who carried the bug. This suggested that H. pylori is involved in protection from sensitivity to pollens and molds, says Dr. Blaser.

"No one would have predicted that the presence or absence of bacteria in your stomach is associated with your sensitivity to pollens and molds," says Dr. Blaser. "But now we have that observation and we can begin to construct a model. One hypothesis is if you have H. pylori in your stomach, you have an inflammatory process that is on-going for decades, and this is skewing the immune response in a particular direction."
-end-
The study was supported by a grant from the National Institute of Environmental Health Sciences, the National Cancer Institute, the National Institutes of Health, the Diane Belfer Program in Human Microbial Ecology, and the Senior Scholar Award of the Ellison Medical Foundation.

NYU Langone Medical Center / New York University School of Medicine

Related Asthma Articles from Brightsurf:

Breastfeeding and risks of allergies and asthma
In an Acta Paediatrica study, exclusive breastfeeding for the first 3 months was linked with a lower risk of respiratory allergies and asthma when children reached 6 years of age.

Researchers make asthma breakthrough
Researchers from Trinity College Dublin have made a breakthrough that may eventually lead to improved therapeutic options for people living with asthma.

Physics vs. asthma
A research team from the MIPT Center for Molecular Mechanisms of Aging and Age-Related Diseases has collaborated with colleagues from the U.S., Canada, France, and Germany to determine the spatial structure of the CysLT1 receptor.

New knowledge on the development of asthma
Researchers at Karolinska Institutet in Sweden have studied which genes are expressed in overactive immune cells in mice with asthma-like inflammation of the airways.

Eating fish may help prevent asthma
A scientist from James Cook University in Australia says an innovative study has revealed new evidence that eating fish can help prevent asthma.

Academic performance of urban children with asthma worse than peers without asthma
A new study published in Annals of Allergy, Asthma and Immunology shows urban children with poorly controlled asthma, particularly those who are ethnic minorities, also suffer academically.

Asthma Controller Step Down Yardstick -- treatment guidance for when asthma improves
The focus for asthma treatment is often stepping up treatment, but clinicians need to know how to step down therapy when symptoms improve.

Asthma management tools improve asthma control and reduce hospital visits
A set of comprehensive asthma management tools helps decrease asthma-related visits to the emergency department, urgent care or hospital and improves patients' asthma control.

Asthma linked to infertility but not among women taking regular asthma preventers
Women with asthma who only use short-acting asthma relievers take longer to become pregnant than other women, according to research published in the European Respiratory Journal.

What are the best ways to diagnose and manage asthma?
A team of experts from The University of Texas Medical Branch at Galveston examined the current information available from many different sources on diagnosing and managing mild to moderate asthma in adults and summarized them.

Read More: Asthma News and Asthma Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.