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Prevalence of CD
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How common is CD? A few years ago it was thought that the prevalence
of CD in Europe varied from 1:300 (one out of 300 people) to 1:2000.
Now the figures vary from 1:90 to 1:600, depending on which study you
look at. These figures are mostly based on studies involving
anonymous blood donors, or screening healthy populations such as
school children. These figures are not based on going to hospitals
and counting the number of diagnosed celiacs.
CD is rare in the Negroid and Asian races, though not unheard of.
This may be because the major starch in China and Africa was not wheat
until fairly recently. So until these populations are exposed to
large amounts of wheat, we may not know what the true prevalence of CD
is in those countries.
The rate of diagnosis of CD seems to be directly related to the level
of suspicion of the doctor, hospital, or health care system. It has
been well-studied in places like Scotland where the rate of diagnosis
in one area is found to be high and then in another area it is much
lower. Then someone with an interest in CD transfers to the second
area and the rate of diagnosis of CD suddenly increases.
There are some population differences that have been noted. For
instance, in Sweden CD is very common and mostly diagnosed in
childhood. But in neighboring Finland CD tends to be diagnosed more
often in adults than in children. In the USA the vast majority are
diagnosed during adulthood. At the University of Iowa the rate is 30
or 40 adults diagnosed with CD for each child. How does one explain
these differences. Is it because the adult doctors aren't looking for
CD in Sweden and the pediatricians aren't looking for it in the USA?
Dr. Murray doesn't think so; he believes there truly is a difference
in the age at which CD is presenting in these countries. At the
Finland symposium there was some discussion on this topic. In Sweden
commercial baby food products have a lot of wheat in them. (In the
past they had lots of milk protein in them, and they changed it 20-30
years ago due to the incidence of milk allergies.)
Incidentally, nearly the exact opposite happened in England & Ireland
in the 1970's. It had been general practice to begin feeding some
type of cereal such as oatmeal to a baby as early as two weeks of age.
Breastfeeding was done only in 10% of the children beyond the age of
six weeks. As a result there were several very young celiacs
diagnosed. However, due to the incidence of CD public health nurses
began advising new mothers to avoid giving gluten to their babies
before the age of one year, and to avoid solids altogether for the
first four months or so. As a result the entire feeding patterns of
infants changed within a year or two and diagnosis of CD in very young
children dropped considerably.
So in Sweden the children are challenged with gluten early in life, so
CD begins presenting early in life; whereas in Ireland gluten is now
avoided early in life, so CD doesn't show up until a later age.
One question that arises: In families with a history of CD, does
exposure to gluten at an early age increase the chances of getting CD?
Nobody knows for sure. Dr. Murray generally advises families with a
history of CD to not feed gluten to a child before the age of one.
Then, once they are a year old, put them on a normal gluten-containing
diet and see what happens. In these cases Dr. Murray recommends that
the child then get the celiac antibody blood tests at age two, or a
full GI evaluation if they develop symptoms or fail to grow.
Is CD really as rare as you might think in the USA? Probably not.
Consider the following:
* 6% of adult Type I diabetics in Iowa have CD.
* A study has shown that 1 in 10,000 people in Utah have DH. That
may not sound too common, but in European countries the incidence
of DH is about the same. And in European countries you usually
get 20 celiac patients for every one DH patient. [That would
make the incidence of CD about 1:500--editor] So if the Utah
study is correct then the rate of CD in Utah should be about the
same as in Europe. Yet the diagnosis rate is much less. Why?
Because either there is a low suspicion of CD among the GI
specialists, or they just aren't seeing all the people who have
CD and don't know it.
Dr. Jarmo Visakorpi is a Finnish researcher who has been studying CD
for about 35 years. He gave the introductory talk at the Finland
symposium and talked about the celiac "iceberg". The analogy is that
the diagnosed cases of CD are like the portion of a floating iceberg
which is above water, and the undiagnosed cases of CD are like the
portion that is below the water. Dr. Visakorpi said that the goal is
to get the entire iceberg above water. This is mostly a reality in
Sweden. In Finland and the rest of Europe some of those peaks are
sticking out of the water. Across the ocean [meaning in North
America] most of the iceberg is underwater.
At the University of Iowa there are 14-17 full-time
gastroenterologists on their staff. Prior to 1990 they diagnosed 2-3
cases of CD a year. Then the numbers started to jump up: 8 cases of
CD diagnosed in 1990; 18 in 1992; 55 or so in 1995, and they are
running at about the same rate again in 1996. Prior to 1990, most of
their newly diagnosed celiac patients presented with either the
"classic" celiac symptoms, DH, or lymphoma. In 1992, only a third of
the newly-diagnosed celiacs fit the representation of classic CD.
Most of them had a single symptom, not multiple symptoms. Half of
them had no diarrhea, and never really had diarrhea at all. Two
thirds of those tested did not have steatorrhea (fatty, smelly
stools).
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