Left handedness may be linked to an increased risk of breast cancer,finds new research published online by the British Medical Journal (26September 2005).
Researchers in the Netherlands examined the relation betweenhandedness and incidence of breast cancer in over 12,000 healthy,middle aged women born between 1932 and 1941.
Body measurements were taken and risk factors such as socialand economic status, smoking habits, family history of breast cancer,and reproductive history were recorded.
They found that left handed women were more than twice aslikely to develop premenopausal breast cancer as non-left handed women.Adjusting for risk factors hardly affected the overall association.
The origin of the association may lie in exposure to highlevels of sex hormones before birth, which can induce left handednessas well as changes in breast tissue, say the authors.
"Although the underlying mechanisms remain elusive, our resultssupport the hypothesis that left handedness is related to increasedrisk of breast cancer," they conclude.
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