A study involving more than 7,000 patients, led by researchers from the NYU Langone Medical Center, New York, New York, showed that children aged between 3 and 19 years are less likely to have asthma if they are H pylori carriers.

"Our findings suggest that absence of H pylori may be one explanation for the increased risk of childhood asthma," said coauthor Yu Chen, PhD, Department of Environmental Medicine, New York University School of Medicine, New York, New York. "Among teens and children ages 3 to 19 years, carriers of H pylori were 25% less likely to have asthma."

The impact was even more potent among children aged 3 to 13 years who were 59% less likely to have asthma if they carried the bacterium. H pylori carriers in teens and children were also 40% less likely to have hay fever and associated allergies such as eczema or rash.

These results, which follow on from similar findings in adults published by the same authors last year, are based on an analysis of data gathered from 7,412 participants in the fourth National Health and Nutrition Survey (NHANES IV) conducted from 1999 to 2000 by the National Center for Health Statistics.

Asthma has been rising steadily for the past half-century while H pylori has been slowly disappearing from developed countries over the past century due to increased antibiotic use, and cleaner water and homes, explains coauthor Martin J. Blaser, MD, NYU Langone Medical Center.

Data from NHANES IV showed that only 5.4% of children born in the 1990s were positive for H pylori and that 11.3% of the participants under age 10 had received an antibiotic in the month prior to the survey.

The rise in asthma over the past decades could stem from the fact that a stomach harbouring H pylori has a different immunological status from one lacking the bug, Dr. Blaser said.

The presence of H pylori may influence how a child's immune system develops and may aid the child's immune system to regulate a response to allergens.

"Our hypothesis is that if you have H pylori you have a greater population of regulatory T-cells that are setting a higher threshold for sensitisation," Dr. Blaser said. "For example, if a child doesn't have H pylori and has contact with 2 or 3 cockroaches, he may get sensitised to them. But if H pylori is directing the immune response, then even if a child comes into contact with many cockroaches, he may not get sensitised because his immune system is more tolerant."

"There's a growing body of data that says that early life use of antibiotics increases risk of asthma, and parents and doctors are using antibiotics like water," Dr. Blaser said. "The reality is that Helicobacter is disappearing extremely rapidly. In the NHANES IV study, less than 6% of US children had Helicobacter, and probably 2 generations ago it was 70%," Dr. Blaser said.

"This is a huge change in human micro-ecology. The disappearance of an organism that's been in the stomach forever and is dominant is likely to have consequences. The consequences may be both good (less likelihood of gastric cancer and ulcers later in life) and bad (more asthma early in life)."


SOURCE: New York University Langone Medical Center

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