Left-handed women’s risk of breast cancer higher-study

By Patricia Reaney

LONDON (Reuters) – 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.

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 pre-menopausal 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 1932-1941 who were part of a breast
screening program. The scientists determined their hand
preference and followed up their medical history to see which
women developed breast cancer.

“If we take pre-menopausal and post-menopausal breast
cancer then there was a 40 percent increased risk,” Uiterwaal
said of left-handed women.

But when they spilled it further the scientists found most
of the excess risk was in breast cancer before the menopause.

“We found that left-handed women are more than twice as
likely to develop pre-menopausal 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 percent to 9 percent of 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 aetiology (cause of the illness),”
Uiterwaal added.

About 5 percent to 10 percent 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.