Stomach Bug Appears to Protect Kids from Asthma
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
Helicobacter pylori, a bacterium that has co-existed with humans for at
least 50,000 years, may lead to peptic ulcers and stomach cancer. H. pylori infection increases the risk of stomach inflammation and stomach ulcers. It also increases the risk of stomach cancer, but only a small number of infected people develop gastric cancer (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 report.
Although H. pylori infection is now recognized as the major cause of both peptic ulcers and gastric cancer (stomach cancer),
and has been classified as a group I carcinogen by the World Health
Organization, physicians are not sure whom to screen and treat with
costly antibiotics, aside from first degree relatives of gastric cancer (stomach cancer) patients and those with Peptic ulcer disease.
New York University
School of Medicine Study on Asthma
“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 report. 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.
About Asthma
Asthma occurs when the main air passages of your lungs, the bronchial
tubes, become inflamed. The muscles of the bronchial walls tighten, and
cells in the lungs produce extra mucus further narrowing your airways.
This can cause minor wheezing to severe difficulty in breathing. In
some cases, your breathing may be so labored that an asthma attack
becomes life-threatening.
Asthma
signs and symptoms can range from mild to severe, ranging from
occasional asthma episodes with mild, short-lived symptoms such as
wheezing to chronic coughing and
wheezing punctuated by severe asthma attacks.
Most asthma attacks are preceded by warning signs, such as shortness of breath, wheezing, and/or tightness in the chest. Recognizing these
warning signs and treating symptoms early can help prevent attacks or
keep them from becoming worse.
About Asthma and H. Pylori
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 H. pylori 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 H. pylori and has contact with two or three
cockroaches, he may get sensitized 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 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 H. pylori 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 H. pylori is
disappearing extremely rapidly. In the NHANES IV study, less than six
percent of U.S. children had H. pylori, 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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