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Breast cancer 'link' to left-handedness

Adam Cresswell, Health editor
September 27, 2005

LEFT-HANDED women are twice as likely to develop breast cancer before they hit menopause compared with right-handed women, researchers will claim today.

A study of women in The Netherlands released by one of the world's top medical journals, speculates that exposure to hormones in the womb could cause both left-handedness and breast cancer risk later in life.

According to the findings, left-handed women are almost 2 1/2 times more likely to have pre-menopausal breast cancer, or 1.39 times more likely across both pre- and post-menopausal women.

However, the results have come under fire from Australian experts, who have criticised the study's methodology as being unreliable.

The paper, published online today by the British Medical Journal, bases its findings on 1426 Dutch women chosen randomly from a larger group of 12,178 women already involved in a separate breast cancer screening study.

Of the 1426 women, 165 were left-handed, and the researchers from the University Medical Centre Utrecht say the increased risk was evident in all left-handed women, except if they were overweight. In which case, the risk did not increase for left-handers.

Helen Zorbas, director of Australia's National Breast Cancer Centre, said the researchers were "drawing a long bow", especially given that the conclusions were based on the experiences of just 165 left-handed women.