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Is modern lifestyle a sickening way to live?
By Rob Stein
The Washington Post

First, asthma cases, hay fever and other common allergic reactions, such as
eczema, shot up. Then pediatricians started seeing more children with food
allergies. Now experts are convinced a suspected jump in lupus, multiple
sclerosis and other afflictions caused by misfiring immune systems is real.

Though the data are stronger for some diseases than others, experts
estimate many allergies and immune-system diseases have doubled, tripled or
even quadrupled in the last few decades, depending on the ailment and
country. Some studies now indicate more than half of the U.S. population
has at least one allergy.

Some researchers suspect the trends all may have a common explanation
rooted in aspects of modern living — including the "hygiene hypothesis"
that blames growing up in increasingly sterile homes, changes in diet, air
pollution, and possibly even obesity and increasingly sedentary lifestyles.

"We have dramatically changed our lives in the last 50 years," said
Fernando Martinez, who studies allergies at the University of Arizona. "We
are exposed to more products. We have people with different backgrounds
being exposed to different environments. We have made our lives more
antiseptic, especially early in life. ... And we may be paying a price for
that."

Along with a flurry of research to confirm and explain the trends,
scientists have also begun testing possible remedies. Some are feeding
high-risk children gradually larger amounts of allergy-inducing foods,
hoping to train the immune system not to overreact. Others are testing
benign bacteria or parts of bacteria. Still others have patients with MS,
colitis and related ailments swallow harmless parasitic worms to try to
calm their bodies' misdirected defenses.

Although hay fever, eczema, asthma and food allergies seem quite different,
they are all "allergic diseases" because they are caused by the immune
system responding to substances that are ordinarily benign, such as pollen
or peanuts. Autoimmune diseases also result from the body's defense
mechanisms malfunctioning. But in these diseases, which include lupus, MS,
type 1 diabetes and inflammatory bowel disease, the immune system attacks
parts of the body such as nerves, the pancreas or digestive tract.

"Overall, there is very little doubt that we have seen significant
increases," said Syed Hasan Arshad, of the David Hide Asthma and Allergy
Centre in England, who focuses on food allergies. "You can call it an
epidemic."

One reason that many researchers suspect something about modern living is
that the increases show up largely in highly developed countries in Europe,
North America and elsewhere, and have only started to rise in other
countries as they have become more developed.

"It's striking," said William Cookson of the Imperial College in London.

The leading theory holds that as modern medicine beats back age-old
bacterial, viral and parasitic diseases, immune systems may fail to learn
how to differentiate between real threats and benign invaders, such as
ragweed pollen or food. Or perhaps because they are not busy fighting real
threats, they overreact or even turn on the body's own tissues.

Several lines of evidence support the theory. Children raised with pets or
older siblings are less likely to develop allergies, possibly because they
are exposed to more microbes. But perhaps the strongest evidence comes from
studies comparing thousands of people who grew up on farms in Europe with
those who lived in less-rural settings. Those reared on farms were
one-tenth as likely to develop diseases such as asthma and hay fever.

"If kids have all sorts of exposures on the farm by being in the stables a
lot, close to the animals and the grasses, and drinking cow's milk from
their own farm, that seems to confer protection," said Erika von Mutius, of
the Ludwig-Maximilians University in Munich.

While the evidence for the hygiene theory is accumulating, many say it
remains far from proven.

"That theory is so full of holes that it's clearly not the whole story,"
said Robert Wood of the Johns Hopkins School of Medicine.

It does not explain, for example, the rise in asthma, because that disease
is more common in poor, inner-city areas where children are exposed to more
cockroaches and rodents that may trigger it, Wood and others said.

Several alternative theories have been presented. Some researchers blame
exposure to fine particles in air pollution, which may give the immune
system more of a hair trigger, especially in genetically predisposed
individuals. Others say obesity and a sedentary lifestyle may play a role.
Still others wonder whether eating more processed food or foods processed
in different ways, or changes in the balance of certain vitamins that can
affect the immune system — such as vitamins C and E and fish oil — are
a factor.

"Cleaning up the food we eat has actually changed what we're eating," said
Thomas Platts-Mills of the University of Virginia.

But many researchers believe the hygiene hypothesis is the strongest, and
the reason one person develops asthma instead of hay fever or eczema or
lupus or MS is because of a genetic predisposition.

"We believe it's about half and half," Cookson said. "You need
environmental factors, and you need genetic susceptibility as well."



http://seattletimes.nwsource.com/html/health/2004261090_immune05.html