Health News
2005-09-27
Being left-handed
could double breast cancer risk
Left-handed women
are more than twice as likely as right-handers to
suffer from breast cancer before reaching menopause, Dutch
Left-handed women
are more than twice as likely as right-handers to
suffer from breast cancer before reaching menopause, Dutch
scientists said on Monday. More than a million women
are diagnosed with breast cancer worldwide each year.
Three quarters of cases occur after menopause, which
usually begins around the age of 50. Some studies have
shown that lesbians are at a higher risk of breast cancer
than heterosexual women of the same age.
Researchers at
the University Medical Center in Utrecht in the
Netherlands speculate that there is a shared origin early in
life for both left-handedness and developing breast
cancer, possibly exposure to hormones in the womb.
"Left-handedness is associated with breast cancer,
most specifically premenopausal breast cancer," said Cuno
Uiterwaal, an assistant professor of clinical epidemiology
at the university, in an interview.
He and his
colleagues studied 12,000 healthy middle-aged women born
between 1932 and 1941 who were part of a breast-screening
program. The scientists determined the hand preference
of each woman and followed up on her medical history
to see which women developed breast cancer.
"If we take
premenopausal and postmenopausal breast cancer, then
there was a 40% increased risk," Uiterwaal said of
left-handed women who participated in the study. Upon
further study, however, the scientists found most of
the excess risk was in breast cancer before menopause.
"We found that left-handed women are more than twice as
likely to develop premenopausal breast cancer as
non-left-handed women," the researchers said in the
report published online by the British Medical Journal.
Other risk
factors such as family history of breast cancer, numbers of
pregnancies, smoking habits, and social and economic status
were considered.
About 8% to 9% of
all women are left-handed. But the scientists said the
findings should not alarm them. "What our study intends to
do is focus on this area. We do not know all the
causes of breast cancer; that is why we should
continue. This may be one new factor that leads us to a
better understanding of the etiology," Uiterwaal added.
About 5% to 10%
of breast cancers are hereditary. Most are due to
mutations in the BRCA1 or BRCA2 genes. The earlier the
illness is diagnosed and treated, the better the
prognosis is for the woman.
"Although the
underlying mechanisms remain elusive, our results
support the hypothesis that left-handedness is related to
increased risk of breast cancer," the researchers
added. (Reuters, with additional reporting by
Advocate.com)
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