Early risers have lower risk of breast cancer, study says

Leslie Hanson
November 8, 2018

It's also known as a circadian rhythm. But not everybody's clock tells the same time. Among morning larks, that figure was roughly one in 100. The Breast Cancer Walk, which centered at the Manhattanville College Campus and directed its way up to SUNY Purchase, totaled five kilometers.

In the study, the researchers looked at data from 409,166 women - some who have had breast cancer, and some without the disease.

The team used a method called "Mendelian randomisation", which uses genetic variants associated with possible risk factors, such as sleep characteristics, to investigate whether they are involved in causing diseases such as breast cancer.

How big is the effect? And obesity is set to become the leading preventable cause of breast cancer for women in the United Kingdom, according to a report from earlier this year. There was less evidence of an association with either insomnia or sleep duration on risk of breast cancer in this study. She is a research fellow in the Cancer Research U.K. Integrative Cancer Epidemiology Program at the University of Bristol. Researchers then mapped the genetic variations between the earlier risers and the night owls and compared it with that to the risk of developing cancer.

Their analysis revealed that women with a preference for mornings reduced the risk of breast cancer by 40%, compared with being an evening type. "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.

Dr Richmond said it was said it was still too soon to give clear advice to women.


Being a morning person is partly down to genetics, so this lowered risk does make some sense. Previous research suggests that night owls have a gene mutation that causes their body clock to run behind, making them go to bed and wake up later than normal.

The American Cancer Society says 45% of cancer deaths in the United States are linked to modifiable risk factors, such as cigarette smoke, excess body weight, eating red and processed meat and physical inactivity.

Science is never 100% sure, but this fits with an emerging picture.

"We know that sleep is important generally for health", said Richmond.

"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", said Rebecca Richmond.

The findings have been published on researchers' website bioRxiv but have not yet gone through scientific peer review.

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