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Updated Mon. Mar. 13 2006 10:40 PM ET

Canadian Press

TORONTO - Children given antibiotics in the first year of life may
have a higher risk of developing asthma - although there is no evidence
the drugs are directly responsible for causing the increasingly common
disease, Canadian researchers say.

In a combined analysis of seven studies involving more than 12,000
youngsters, researchers at the University of British Columbia found
that those prescribed antibiotics before their first birthday were more
than twice as likely as untreated kids to develop asthma in childhood.

Furthermore, multiple exposure to antibiotics appeared to bump up the
risk even higher - 16 per cent for every course of the drugs taken
before age one, said co-principal investigator Carlo Marra, a professor
of pharmaceutical science at the University of British Columbia.

Young children are often prescribed antibiotics for upper respiratory
and middle-ear infections, even though many of those diseases turn out
to be viral in origin. Antibiotics work only against bacteria.

"It appears that it is certainly possible that there is an association"
between early antibiotic use and subsequent asthma, Marra said Monday
from Vancouver. "Given that, it makes even more sense for people to use
antibiotics judiciously. Not, 'Don't use antibiotics,' but only use
them when they're necessary."

Still, Marra said "you have to be careful not to over-interpret the
findings. . . . This is more evidence that there is potential adverse
events associated with (antibiotics), asthma being one of them.

"But can we say for certain antibiotics cause asthma? No we can't."

What the drugs may do is contribute to a state of excess hygiene, which
is a possible reason for rising rates of childhood asthma in Canada and
other western countries. The "hygiene hypothesis" suggests that one
reason behind the asthma epidemic is that children have too little
exposure to microbes, in part because of widespread antibiotic use.

Limited exposure to germs can lead to an over-sensitive immune system,
which mounts an over-the-top response to such non-threatening agents as
pollen and dust mites. The result is an allergic reaction, which in
some people can include the airway inflammation that's the hallmark of
asthma.

About 15 per cent of Canadian children develop asthma, a rate double
that of 15 to 20 years ago, said Dr. Felix Ratjen, chief of respirology
medicine at Toronto's Hospital for Sick Children.

Commenting on the study published Tuesday in the journal Chest, Ratjen
said the findings are not definitive because there are so many factors
that could contribute to asthma.

"This is just an interesting observation that may or may not be true
and the data are not convincing in one way or another," said Ratjen,
who was not involved in the study.

Teasing out the role of antibiotics would be a complex task, said
Ratjen, noting that some babies who come to the doctor wheezing - and
are treated for a respiratory infection - are actually exhibiting the
first signs of asthma and get misdiagnosed.

He cautioned that parents should not avoid antibiotics for their
children - when necessary - because of a fear the medication may make
them prone to asthma.

"In terms of antibiotics, that can be rather risky because certainly
antibiotics are very important in fighting bacterial infections. And if
a child has a bacterial infection and is not treated, this child will
be at risk."

Toronto allergist Dr. Mark Greenwald, vice-president of the Asthma
Society of Canada, said the analysis raises lots of questions about
society's possible role in promoting asthma, which afflicts about 3.3
million Canadians of all ages.

"What is interesting is the theoretical stuff: Are we too clean? Are we
using too many antibiotics? Should kids go through a number of
infections and survive them?

"We know that there are too much antibiotics out there anyway,"
Greenwald said. "So are we compounding our own problems? It's a
question, not an answer."

That's one of the issues Marra's team will try to tackle in a study of
200,000 B.C. infants, who will be followed after birth to look at the
incidence of asthma and possible causative factors. Among the questions
researchers will ask is: if antibiotics do contribute to asthma, are
some classes of the drugs bigger culprits than others?

"Certainly based upon the evidence we have today, there very well may
be an association and folks should be cognizant that we use too many
antibiotics now," Marra said. "I'm not convinced there isn't a
causation from what we found."

http://www.webmd.com/content/Article/119/113554.htm

Studies Suggest Risk Is Double for Treated Babies By Salynn Boyles
WebMD Medical News  Reviewed By Louise Chang, MD
on Monday, March 13, 2006

More From WebMD

March 13, 2006 -- Babies treated with even one course of antibiotics
during their first year of life may have twice the risk of developing
asthma later in childhood as unexposed babies, an analysis of past
research shows.

The findings bolster the theory that an increase in the use of
antibiotics early in life may be a factor in the epidemic rise in
childhood asthma. They also suggest that greater exposure to
antibiotics is associated with greater asthma risk.

Approximately one in eight children in the U.S. has asthma, and asthma
rates among children under age 5 have increased especially between 1980
and the mid-1990s, according to figures from the CDC.

While results from the pooled studies point to a link between early
antibiotic exposure and asthma, they fall short of proving the
association, says Carlo A. Marra, PhD, PharmD, of the University of
British Columbia.

"Antibiotic exposure during the first year of life does appear to be a
risk factor for the development of childhood asthma, but because of
limitations in the studies we reviewed we have to conclude that bigger
and better studies are still needed," he tells WebMD.

Different Studies, Different Findings

The association between early antibiotic use and childhood asthma was
significantly stronger in studies that relied on parent recall than in
those that followed children over time.

Marra says the recall, or retrospective, studies may have been
compromised by bias. Specifically, the parents of the children with
asthma may have been more likely to report early antibiotic exposures
than parents of children without asthma.

An analysis of five studies that examined the effect of treating
infants with multiple courses of antibiotics showed that greater
exposure to the drugs was associated with greater asthma risk. But this
association was again seen in the retrospective studies.

The study is published in the March issue of the journal Chest.

Hygiene Hypothesis

While not conclusive, Marra says the findings offer some of the
strongest supporting evidence yet in favor of the so-called 'hygiene
hypothesis,' which suggests that increasingly sterile environments may
be making children more susceptible to allergies and asthma.

Early use of antibiotics has been implicated because the drugs kill
good bacteria in the gut, which may, in turn, weaken the immune system.

Allergist Clifford W. Bassett, MD, FAAAAI, says the analysis
illustrates the potential importance of early environmental exposures
in future health.

He adds that it is up to pediatricians and other doctors who treat
babies and children to educate parents about when antibiotics are
beneficial and when they are not.

Traditional antibiotics are useful for the treatment of bacterial
infections but are of no use in the treatment of viral infections such
as colds and flu.

Bassett is with The Long Island College Hospital in Brooklyn, N.Y. He
is also vice chairman of the public education committee of the American
Academy of Allergy, Asthma, and Immunology.

"Clearly, you wouldn't want to withhold an antibiotic when it is needed
because of a theoretical risk of asthma," he says. "But this research
does underscore the importance of not overusing these drugs, especially
early in life."

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SOURCES: Marra, F. Chest, March 2006; vol 129: pp 610-618. Carlo A.
Marra, PharmD, PhD, assistant professor of pharmaceutical sciences,
University of British Columbia, Vancouver. CDC Surveillance for Asthma,
Morbidity and Mortality Weekly Report, 1998; vol 47 (SS-1). Summary
Health Statistics for US Children, 2004, NCHS, CDC. Clifford W.
Bassett, MD, FAAAAI, allergist, The Long Island College Hospital,
Brooklyn, N.Y.; vice chairman for public education, American Academy of
Allergy, Asthma, and Immunology.