SATURDAY, Nov. 13 (HealthDay News) -- It's a common belief that
as you get older, your allergy symptoms will wane, but a new study
suggests it's possible that even more older people will be
experiencing allergies than ever before.
In a nationally representative sample of people, researchers
found that IgE antibody levels -- that's the immune system
substance that triggers the release of histamine, which then causes
the symptoms of allergies like runny nose and watery eyes -- have
more than doubled in people older than 55 since the 1970s.
IgE levels don't always directly correlate with the presence of
allergies or consistently indicate their severity, but IgE is the
main antibody involved in allergies, explained study author Dr.
Zachary Jacobs, a fellow in allergy and immunology at Children's
Mercy Hospital and Clinic in Kansas City, Mo.
"With IgE levels, it's hard to make an inference for a specific individual, but we're reporting a population trend, and it looks like there's increased allergic sensitization. It looks like Americans have more allergies now than they did 25 or 30 years ago," Jacobs said.
And, he added, "People in their 50s almost certainly have more
allergy now than they did 25 or 30 years ago, and more allergists
will be needed for the baby boomers."
The findings are to be presented Saturday at the American
College of Allergy, Asthma and Immunology annual meeting, in
Jacobs and his colleagues noticed that no one had looked at
levels of IgE in the population since the 1970s, when a large study
called the Tucson Epidemiological Study was done.
The new study compared data from the Tucson study in the '70s to
data from the more recent National Health and Nutrition Examination
Survey (NHANES) from 2005 to 2006.
There were 7,398 people enrolled in NHANES, while the Tucson
study included 2,743 people. The demographic profiles for the two
studies were similar, although there were slightly more young
people (under 24) in the NHANES study.
IgE levels, which are measured with a blood test, however, were
not always the same. The Tucson study group had higher IgE levels
in only one age group -- 6- to 14-year-olds. In all other age
groups, the NHANES participants had significantly higher IgE
The difference was most striking in the older age groups. For
example, in those aged 55 to 64, IgE levels among NHANES
participants were more than double those of the Tucson group.
Jacobs said his researchers didn't think better testing methods
could account for this difference. If better tests were a factor,
he said, the differences would have stayed the same across the
ages, but in the younger group, IgE levels were lower in the NHANES
study compared to the Tucson group.
Jacobs said there are numerous factors that could be at play,
but all are hypotheses. He said the "hygiene hypothesis" is a
popular theory. The hygiene hypothesis essentially means humans are
now living in a world that's too clean, even wiping out good
bacteria and leaving the immune system to fight off only the most
harmless of foreign substances. Another possibility is the
potential of global warming, which could be causing higher CO2
levels and more pollen, theoretically contributing to the rise in
allergic disease, he said.
Dr. Jennifer Appleyard is chief of allergy and immunology at St.
John Hospital and Medical Center in Detroit. She said: "The common
wisdom is that IgE production typically drops as you get older. So,
to see a general trend like this is surprising."
"IgE reflects much more than just allergy. It can be affected by many things, like smoking, parasitic diseases and eczema. So it's not just affected by or represented by allergy, and levels of IgE aren't directly correlated with severity of disease. But this study's findings are interesting, and definitely bear further evaluation," Appleyard added.
Learn more about allergies from the
U.S. National Library of Medicine.
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