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Stomach Bug Appears To Protect Kids From Asthma, Says New Study
ScienceDaily (July 20, 2008) ‹ A long-time microbial inhabitant of the
human stomach may protect children from developing asthma, according to
a new study among more than 7,000 subjects led by NYU Langone Medical
Center researchers. Helicobacter pylori, a bacterium that has co-existed
with humans for at least 50,000 years, may lead to peptic ulcers and
stomach cancer. Yet, kids between the ages of 3 and 13 are nearly 59
percent less likely to have asthma if they carry the bug, the
researchers re****t.
The study appears in the July 15, 2008, online issue of The Journal of
Infectious Diseases.
"Our findings suggest that absence of H. pylori may be one explanation
for the increased risk of childhood asthma," says Yu Chen, Ph.D.,
assistant professor of epidemiology at New York University School of
Medicine and a co-author of the study. "Among teens and children ages 3
to 19 years, carriers of H. pylori were 25 percent less likely to have
asthma."
The impact was even more potent among children ages 3 to 13: they were
59 percent less likely to have asthma if they carried the bacterium, the
researchers re****t. H. pylori carriers in teens and children were also
40 percent 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.
Dr. Chen collaborated on the survey with Martin J. Blaser, M.D., the
Frederick H. King Professor of Internal Medicine, chair of the
department of medicine, and professor of microbiology at NYU Langone
Medical Center. Dr. Blaser has studied H. pylori for more than two
decades.
Asthma has been rising steadily for the past half-century. Meanwhile H.
pylori, once nearly universal in humans, has been slowly disappearing
from developed countries over the past century due to increased
antibiotic use, which kills off the bacteria, and cleaner water and
homes, explains Dr. Blaser. Data from NHANES IV showed that only 5.4
percent of children born in the 1990s were positive for H. pylori, and
that 11.3 percent of the participants under 10 had received an
antibiotic in the month prior to the survey.
The rise in asthma over the past decades, Dr. Blaser says, could stem
from the fact that a stomach harboring H. pylori has a different
immunological status from one lacking the bug. When H. pylori is
present, the stomach is lined with immune cells called regulatory T
cells that control the body's response to invaders. Without these cells,
a child can be more sensitive to allergens.
"Our hypothesis is that if you have Helicobacter you have a greater
population of regulatory T-cells that are setting a higher threshold for
sensitization," Dr. Blaser explains. "For example, if a child doesn't
have Helicobacter and has contact with two or three cockroaches, he may
get sensitized to them. But if Helicobacter is directing the immune
response, then even if a child comes into contact with many cockroaches
he may not get sensitized because his immune system is more tolerant."
In other words, the presence of the bacteria in the stomach may
influence how a child's immune system develops: if a child does not
encounter Helicobacter early on, the immune system may not learn how to
regulate a response to allergens. Therefore, the child may be more
likely to mount the kinds of inflammatory responses that trigger asthma.
"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 says. "The reality is that
Helicobacter is disappearing extremely rapidly. In the NHANES IV study,
less than six percent of U.S. children had Helicobacter, and probably
two generations ago it was 70 percent. So, 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."
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Adapted from materials provided by NYU Langone Medical Center / New York
University School of Medicine.
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