'Impaired Glucose Tolerance Tied
to Increased Risk of Cancer Mortality
Hyperinsulinemia may promote cancer development,
since insulin has been shown to stimulate cell
growth, especially colonic epithelial cells.
Those are the findings which, provide yet another
reason to modify a sedentary lifestyle for the
estimated 15% of US adults with impaired glucose
tolerance.
"The finding may also explain why overweight
people are more likely to develop cancer, especially
colon cancer," Dr. Saydah, from Johns Hopkins
University in Baltimore, added.
In a study of more than 3,000 adults followed
between 1976 and 1980, she and her colleagues
found that people with impaired glucose tolerance
were nearly twice as likely to die from any type
of cancer than were those with normal glucose
levels. Their risk of dying from colon cancer,
specifically, was more than quadruple that of
healthy controls.
After adjusting for age, sex and other factors
associated with cancer risk, "abnormal glucose
tolerance remained strongly associated with cancer
mortality," the researchers report in the
June 15th issue of the American Journal of Epidemiology.
The reason for the link is unclear. Previous reports
have suggested that hyperinsulinemia may promote
cancer development, since insulin has been shown
to stimulate cell growth, especially colonic epithelial
cells.
However, people with overt diabetes were no more
likely to die of cancer than were people with
normal blood sugar levels. Again, the reasons
are unclear, but Dr. Saydah offered several possible
explanations.
"As a person moves from normal glucose tolerance
to impaired glucose tolerance to diabetes, their
insulin levels increase rapidly and then gradually
decline," she said. This decline "may
slow the cancer growth since there is not as much
insulin or associated growth factors available
for the cells."
Another potential reason, Dr. Saydah pointed out,
is that given that cardiovascular disease is the
leading cause of death among people with diabetes,
it may be that people with diabetes have undiagnosed
cancer and are simply dying from cardiovascular
disease first.
A third possibility, Dr. Saydah said, is that
diabetes might offer some type of protective effect.
"The theory behind this is that the blood
vessels of individuals with diabetes are stiffer...possibly
making it more difficult for cancer cells to spread
throughout the body," she explained. Am J
Epidemiol 2003;157:1092-1100
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FACT:
Isolated postprandial hyperglycemia (2-hour postprandial
glucose level >140 mg/dL [>7.8 mmol/L])
and normal hemoglobin A1c (<6.1%) values is
associated with a 2-fold increased risk of death
from cardiovascular disease. These observations
imply that more strict glycemic control is required
to prevent macrovascular disease than microvascular
disease. Arch Intern Med 2003 Jun 9;163(11):1306-16
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