PROSTATE CANCER RISK REDUCED BY SLEEPING WITH MANY WOMEN , BUT NOT INCREASED WITH MANY MEN
Compared to men who have had only one partner during their lifetime,
having sex with more than 20 women is associated with a 28% lower risk of one
day being diagnosed with prostate cancer, according to researchers at the
University of Montreal and INRS -- Institut Armand-Frappier. However, having
more than 20 male partners in one's lifetime is associated with a twofold
higher risk of getting prostate cancer compared to those who have never slept
with a man
Marie-Elise
Parent and Marie-Claude Rousseau, professors at university's School of Public
Health, and their colleague Andrea Spence, published their findings in the
journal Cancer Epidemiology.
The results were obtained as part of the Montreal study PROtEuS (Prostate Cancer
& Environment Study), in which 3,208 men responded to a questionnaire on,
amongst other things, their sex lives. Of these men, 1,590 were diagnosed with
prostate cancer between September 2005 and August 2009, while 1,618 men were
part of the control group.
Risk
associated with number of partners
Overall,
men with prostate cancer were twice as likely as others to have a relative with
cancer. However, evidence suggests that the number of sexual partners affects
the development of the cancer.
Consequently,
men who said they had never had sexual intercourse were almost twice as likely
to be diagnosed with prostate cancer as those who said they had. When a man has
slept with more than 20 women during his lifetime there is a 28% reduction in
the risk of having prostate cancer (all types), and a 19% reduction for
aggressive types of cancer. "It is possible that having many female sexual
partners results in a higher frequency of ejaculations, whose protective effect
against prostate cancer has been previously observed in cohort studies,"
Parent explained.
According
to some studies, the underlying mechanism of this protective effect is in
reducing the concentration of cancer-causing substances in prostatic fluid or
lowering the production of intraluminal crystalloids. It should be noted that
for all participants, the age at which they first had sexual intercourse or the
number of sexually transmitted infections (STIs) they had contracted did not
affect the risk of prostate cancer. Moreover, only 12% of all participants
reported having had at least one STI in their lifetime, which is few.
Male
partners and increased risk
Parent
and her team can only formulate "highly speculative" hypotheses to
explain this association. "It could come from greater exposure to STIs, or
it could be that anal intercourse produces physical trauma to the
prostate," Parent said.
Avenues
for further research
Parent,
Rousseau, and Spence are specialists in prostate cancer and are the first
research team to suggest that the number of female partners is inversely
associated with the risk of developing cancer.
"We
were fortunate to have participants from Montreal who were comfortable talking
about their sexuality, no matter what sexual experiences they have had, and
this openness would probably not have been the same 20 or 30 years ago,"
Parent explained. "Indeed, thanks to them, we now know that the number and
type of partners must be taken into account to better understand the causes of
prostate cancer." Does this mean public health authorities will soon be
recommending men to sleep with many women in their lives? "We're not there
yet," Parent said.
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