"What on earth does diabetes
have to do with prostate cancer?" wonders Mike Wilson,
a 52-year-old diabetic, as he shoots some insulin into
his arm. Quite a bit, according to a paper in the May
15 issue of American Journal of Epidemiology that
bolsters the paradoxical view that diabetes can be beneficial.
Apparently, the disease may actually protect against prostate
cancer.
Previous studies have offered
hints that reduced insulin levels, the hallmark of diabetes,
may actually knock down the risk of prostate cancer.
This is because low insulin levels can go hand in hand
with lower levels of testosterone, according to Dr Kangmin
Zhu of the United States Military Cancer Institute in
Washington. However, this aspect of diabetes had not
been rigorously investigated.
To get the real scoop, Dr Zhu and his colleagues used
data that had been compiled as part of the Physician's
Health Study, which collected data on the health of
over 22,000 US male physicians aged 40 to 84 between
1982 and 1987. Of these docs, 1,110 were diagnosed with
prostate cancer during that time. Dr Zhu was able to
obtain the medical records of these men, as the progress
of their disease was followed from 1982 to 1995. As
controls, the researchers selected an equal number of
men of similar age who did not have prostate cancer
and whose medical histories were available during the
same time period.
When the data was put through statistical analysis machinery
to sort the wheat from the chaff, the odds ratio or
the likelihood of prostate cancer occurring in men with
diabetes was 0.64 when compared to the incidence of
disease in guys without diabetes. To put it another
way, men with diabetes had about two-thirds less chance
of developing prostate cancer.
The study also found that it's not size that mattered
but rather the length of time men had diabetes before
a prostate cancer diagnosis. Those who had been diagnosed
with diabetes for over 10 years had an even lower chance
of developing prostate cancer than patients who had
had diabetes for less time than that.
Diabetes' protective effect also extended to the degree
of spread of the cancer. The odds of the cancer spreading
to other tissues were lower in diabetics. A consequence
of this was that these smaller cancers tended to be
more successfully treated.
The authors write that a larger study will be needed
to really hammer home the reality of their findings.
But for now the study points the way to understanding
factors that delay prostate cancer progression and offers
a silver lining to people like Mike when the dark cloud
of a diabetes diagnosis descends.
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