Impaired glucose tolerance significantly increases risk for death from colorectal and other cancers
People with impaired glucose tolerance,
a condition considered a precursor to diabetes, are at increased
risk for death from colorectal and other cancers, according to an
article in the June 15th issue of the American Journal of Epidemiology.
In the current study, American researchers
conducted a prospective cohort study with use of data from 2 national
studies representing a total of 3,054 adults aged 30 to 74 years
at baseline (1976-1980), none of whom had baseline cancer. Participants
were classified as diagnosed diabetes (247 adults), undiagnosed
diabetes (180 adults), impaired glucose tolerance (477 adults),
or normal glucose tolerance (2,250 adults).
People with impaired glucose tolerance had a nearly 2-fold increase
in risk for cancer death and more than 4 times as likely to die
from colorectal cancer as peers with normal glucose tolerance.
"By contrast, adults with outright diabetes
had little or no association with risk of cancer death (relative
hazard 1.13 versus 1.87 for people with impaired glucose tolerance),"
said senior study author Frederick L. Brancati, M.D.
The mechanism underlying the apparent increase
in risk is not clear, Brancati said, although previous studies have
suggested that high levels of insulin can act as a growth factor
in promoting development of cancer cells.
Impaired glucose tolerance, which is present
in about 15 percent of American adults, is defined as blood glucose
levels that are higher than normal but not high enough to be classified
as diabetes. Roughly 33 percent of affected people develop diabetes
within 5 years. Although there are no proven methods for prevention
of the condition, according to Brancati, most affected people are
overweight and sedentary. Weight loss and increased exercise are
usually recommended.
An analysis of study participants showed
that people with impaired glucose tolerance (compared with those
having normal glucose tolerance) were more likely to be older, female,
less educated, and relatively sedentary. They also were less likely
to be current smokers or to drink 1 or more alcoholic drinks per
week. In addition, they had greater body fat, lower high-density
lipoprotein cholesterol, and higher total cholesterol, triglycerides,
and blood pressure.
Researchers confirmed deaths in the study
groups occurring between 1976 and 1992 by search of national files.
Of 737 participant deaths during the study period, 206 (28 percent)
were from cancer. People with impaired glucose tolerance had the
highest cancer death rate, followed by those with undiagnosed diabetes,
diagnosed diabetes, and normal glucose tolerance. The authors suggest
that impaired glucose tolerance be considered an independent predictor
for cancer mortality.
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