"Morning people" have a lower risk of breast cancer

According to British researchers, women whose body clocks mean that they are "morning people" are at lower risk of developing breast cancer.

The Bristol University team explains why it remains to be discovered.

He adds that the results are important because they can affect the risk of each woman.

The experts said the study presented at the CNRI cancer conference in Glasgow helped to better understand the importance of sleep for health.

Biological clock

Everyone has a biological clock that governs the functioning of the body every 24 hours or so. It is also called circadian rhythm.

It affects everything from sleep to mood, to the risk of heart attack.

But not everyone has the same time.

Morning people or "larks" get up early, reach their maximum earlier in the day and get tired earlier in the evening.

Evening people or "owls" have more difficulty getting up in the morning, are productive later in the evening and prefer to go to bed late.

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Answer our quiz to find out if you are the morning or evening.

And this is involved in breast cancer?

The researchers think so. They used a new intelligent method of data analysis, called Mendelian Randomization.

They examined 341 DNA extracts (the instructions for the human body) to determine if we are likely to be a lark or an owl.

They used this knowledge to perform an experiment on more than 180,000 women in the British Biobank project and nearly 230,000 women in the Breast Cancer Association Consortium study.

They showed that people genetically programmed to be "larks" were less likely to have breast cancer than those scheduled to be owls.

Since these DNA fragments are fixed at birth and are not related to other known causes of cancer, such as obesity, this means that researchers are reasonably confident that body clocks are involved in cancer.

How big is the effect?

In the UK, about one in seven women will develop breast cancer in their lifetime.

But this study only focused on a glimpse of a woman's life, carried out in eight years.

During this time, it was found that two in every 100 owls had developed breast cancer, compared to one in 100.

Dr. Rebecca Richmond, one of the researchers at the University of Bristol, told the BBC: "The results are potentially very important because sleep is ubiquitous and easily altered.

"Previous research has examined the impact of shift work, but it shows that there can be a risk factor for all women."

Age and family history are among the major risk factors for breast cancer. According to Cancer Research UK, about a quarter of cases could be avoided.

Will a good night's sleep prevent me from getting cancer?

It is not so simple.

Dr. Richmond stated that it was still too early to give clear advice to women.

She told the BBC: "We still have to understand what makes an evening person more at risk than a morning person … we have to disorganize the relationship."

Is it something about the biological clock itself? Or do "owls" cause harm by living out of time with their biological clock in order to get up and go to work? Does the biological clock affect hormone levels to alter the risk of cancer, immune system or metabolism?

There are still many unanswered questions.

Are the researchers right?

Science is never 100% sure, but it is an emerging image.

The World Health Organization has already stated that the disruption of people's biological clock due to shift work was probably related to the risk of cancer.

Dr. Richard Berks of Breast Cancer Now said, "These intriguing findings add to the growing body of evidence that there is some overlap between the timing of our preferred sleeping time and our risk of breast cancer. Further research is needed to unravel the details of this relationship. "

Similar studies have revealed a role in sleep preferences and mental health, including the risk of schizophrenia.

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

"These are interesting findings that provide further evidence of how our biological clock and our natural preference for sleep are involved in the onset of breast cancer."

The results have been published on the bioRxiv researchers' website but have not yet been peer reviewed by scientists.

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