'Morning people' at lower risk of breast cancer?

BIG DAY OUT Marilyn Rice and Jo Maundrell

BIG DAY OUT Marilyn Rice and Jo Maundrell

Morning people who peak in the early hours of the day are less at risk of breast cancer compared to their "evening" counterparts, a study has found.

The data from the BCAC group of participants showed that women who were morning types, also known as "larks", had a 40 per cent reduced risk of breast cancer compared with those who were evening types, or "owls". Also, the research notes that women who slept longer than seven to eight hours had a 20 percent increased risk per additional hour slept.

Cancer risks associated with a person's body clock and sleep patterns have been reported in previous research and the United Kingdom researchers wanted to explore sleep traits in more detail, as well as any genetic factors underlying this.

'In other words, it may not be the case that changing your habits changes your risk of breast cancer; it may be more complex than that.

This echoes previous studies which found night-shift workers and those exposed to more artificial light at night are at greater risk of cancer. The findings, which have not been peer-reviewed, were presented at the NCRI Cancer Conference in Glasgow, Scotland, from Sunday through Tuesday.

Around one in seven women in the United Kingdom will develop breast cancer in their lifetime.

Cliona Kirwan, consultant breast surgeon and researcher at the University of Manchester, said: "The use of Mendelian randomisation in this study enables the researchers to examine the causal effect on breast cancer of different sleep patterns".

The researchers believe their findings have implications for policy-makers and employers.

The team speculated that this mismatch may have its own impact on cancer risk, but making that connection will require more extensive research. The World Health Organization already says disruption to people's body clocks because of shift work is probably linked to cancer risk.

"The statistical method used in this study, called Mendelian randomization, does not always allow causality to be inferred", said Dipender Gill, clinical research training fellow at Imperial College London.

"The authors do not show any biological mechanism by which sleep timing preference could influence breast cancer risk".

So will a good night's sleep stop me getting cancer?

She tells the BBC: "We still need to get at what makes an evening person more at risk than a morning person... we need to unpick the relationship". "I wouldn't support that women should get up earlier to reduce risk of breast cancer". This study provides further evidence to suggest disrupted sleep patterns may have a role in cancer development.

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