Women who are considered morning people are less likely to develop breast cancer than those who have more energy in the evenings, according to researchers.
Researchers have found that women who prefer to get up and go to be early have a 40 to 48 per cent lower risk of breast cancer than those whose body clock leads them to feel drowsy in the morning and most energetic in the evening.
Researchers also found that sleeping beyond the recommended seven to eight hours was linked to a 20 per cent increased risk of the disease per additional hour slept.
Dr Rebecca Richmond, from Bristol, said: 'We would like to do further work to investigate the mechanisms underpinning these results, as the estimates obtained are based on questions related to morning or evening preference rather than actually whether people get up earlier or later in the day.
But the team point out that many factors are involved in a person developing breast cancer and that these numbers are not an absolute risk. Experts said the study presented at the NCRI Cancer Conference in Glasgow added to a growing understanding of the importance of sleep in all health.
"More work is needed to understand why sleep characteristics may be linked to breast cancer risk".
They looked at 341 snippets of DNA (the instructions for the human body) that control whether we are likely to be a lark or an owl. They used a clever new way of analysing data - called Mendelian randomisation.
Take our quiz to find out whether you are a morning type, or an evening owl.
In 2018, it is estimated that 627,000 women passed away from breast cancer, that is approximately 15% of all cancer deaths among women. "These findings have potential policy implications for influencing sleep habits of the general population in order to improve health and reduce the risk of breast cancer among women".
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She is a research fellow in the Cancer Research U.K. Integrative Cancer Epidemiology Program at the University of Bristol.
Age and family history are some of the main risk factors for breast cancer.
The Chief Executive Officer, AXA Mansard Health Limited, Mr Tope Adeniyi, said, "There is still no sure way to prevent breast cancer yet. Another limitation is that sleep timing preference (chronotype) is self-reported, and the investigation did not specifically recruit individuals with different sleep patterns, such as night-shift workers", Burgess wrote in the comments of the study.