Women who are "larks", working better at the beginning of the day than at the end of the day, have a lower risk of breast cancer, according to a new research led by the University of Bristol presented at the NCRI Cancer Conference of 2018 today [Tuesday 6 November].
The study of several hundred thousand women, who was investigating whether the way people sleep could contribute to the development of breast cancer, also found some evidence of a causal link between sleeping for longer breast cancer and breast cancer.
A Dra. Rebecca Richmond, researcher of the Cancer Research UK's Integrative Epidemiology Program and the MRC's Integrative Epidemiology Unit at Bristol University and colleagues, analyzed data from 180,215 women enrolled in the Biobank project in the United Kingdom and 228,951 women who were part of a study of the association of breast cancer genome carried out by the International Association of the Breast Cancer Association (BCAC), which has the largest collection of genetic data on women with breast cancer obtained so far.
"Using the genetic variants associated with the preference of people in the morning or at night, the duration of sleep and insomnia, which have previously been identified by three studies of recent United Kingdom bio genomics of the genome, we investigate whether these traces of sleep have a causal contribution At the risk of developing chest cancer, "he said.
The team used a method called "Mendelian randomization," which uses genetic variants associated with possible risk factors, such as sleep characteristics, to investigate if they are involved in causing diseases such as breast cancer.
The analysis of Mendelian randomization, which included data from the BCAC of 122,977 cases of breast cancer and 105,974 women without the disease (the controls), found that morning preference reduced the risk of breast cancer by 40 percent compared to one type of night (an "owl"). He also found that women who slept more than seven to eight recommended hours had a 20% risk of illness for additional hour sleeping. 
The analysis of data obtained from women from the UK Biobanc (2,740 new cases of breast cancer and 149,064 controls) found similar results; Morning preference reduced the risk of breast cancer by 48%. The analysis of Mendelian randomization of these data revealed that approximately a person less than 100 will develop breast cancer if they have a preference in the morning compared to people who have a preference at night. There was less evidence of association with sleep insomnia or duration of the risk of breast cancer in this study.
Dr. Richmond said: "We want to do more work to investigate the mechanisms that support these results, since the estimates obtained are based on issues related to the preference of tomorrow or night instead of if people get up before or after the day. In words, it may not be the case that changing your habits change the risk of having breast cancer – it can be more complex.
"However, the results of a protective effect of tomorrow's preference on the risk of breast cancer in our study are consistent with previous research, highlighting a role for night shift work and exposure to" night light "as risk factors for Breast cancer.
"We also found evidence of a causal effect of the increase in sleep duration and the fragmentation of sleep on breast cancer, which was evaluated using objective sleep measures obtained from the motion monitors used by about 85,000 Biobank participants in the Kingdom United
"The method of Mendelian randomization applied in this investigation is particularly useful in the identification of causal risk factors for the disease since the genetic variants identified in relation to the characteristics of the dream are not susceptible to being influenced by any external or environmental factor, nor by the development of cancer., and can, therefore, be used to determine cause and effect relationships. "
Researchers believe that their results have implications for policy makers and entrepreneurs. Dr Richmond said: "These results have potential political implications for influencing the sleep habits of the general population to improve health and reduce the risk of breast cancer among women."
Dr. Richmond and his colleagues plan to investigate the mechanisms that underlie the effects of different sleep characteristics on the risk of developing breast cancer. "We want to use genetic data from large populations to further understand how to stop the body's body clock from contributing to the risk of breast cancer," he said.
Mrs. Clara Clare Kirwan, from the University of Manchester, a member of the NCRI Mama Clinic Study Group and who did not participate in this investigation, said: "These are interesting results that provide more evidence of how our body clock and our natural preference Sleep is involved in the onset of breast cancer.
"We know that night shift work is associated with worse physical and mental health. This study provides more evidence to suggest that suspended sleep patterns may have a role in the development of cancer. The use of Mendelian randomization in this study allows Researchers examine the cause Effect on breast cancer with different patterns of sleep observing the variations of specific genes already known associated with the characteristics of sleep. This helps to avoid misleading conclusions that could be affected by confounding factors. "
"Investigate the causal relationships between the characteristics of sleep and the risk of breast cancer: a study of Mendelian randomization" by Dr. Richmond et al presented at the NCRI Cancer Conference of 2018
More information Some of the percentages and case numbers in this press release have been updated since the summary was presented.
The study was financed by Cancer Research UK and the Medical Research Council.
About the NCRI Cancer Conference
The NCRI Cancer Conference is the largest UK forum that shows the latest advances in cancer research. The Conference offers a platform for researchers, clinicians, people affected by cancer and representatives of the industry to come together to discuss, present and show high quality research. The informative and interactive educational sessions attract more than 1,500 delegates each year and create the ideal setting to establish new collaborations with the main interest groups in cancer research.
The NCRI Cancer Conference is being held between 4-6 November 2018 at the Campus of Scotland, Glasgow, United Kingdom.
For more information visit https://conference.ncri.org.uk/
About the NCRI
The National Cancer Research Institute (NCRI) is an association of cancer researchers throughout the United Kingdom, established in 2001. Its 19 member organizations work together to accelerate progress in cancer-related research through collaboration to improve health and quality of life.
NCRI works to coordinate cancer research, to improve the quality and relevance of the research and to accelerate the translation of clinical practice research into the benefit of patients.
NCRI's partners are: Research Council of Biotechnology and Biological Sciences (BBSRC); Bloodwise; Research of the brain tumor; Breast cancer now; Cancer Research UK; Children with cancer in the United Kingdom; Department of Health and Social Services; Council for Economic and Social Research (ESRC); Macmillan Cancer Support; Marie Curie; Medical Research Council (MRC); Public Health Agency of Northern Ireland (Department of Research and Development); Research Fund on Pancreatic Cancer; Prostate Cancer UK; Roy Castle's Lung Cancer Foundation; Health administrations of the Scottish government (Chiefs of Scientists); Tenovus Care of Cancer; The Wellcome Trust and the Government of the Welsh Assembly (Health and Care Research Wales).
For more information visit www.ncri.org.uk