Scientists are stunned by the discovery of large breast cancer

Scientists are stunned by the discovery of large breast cancer – Researchers at Harvard University have only made a startling discovery regarding breast cancer, so finding that girls who reside in regions with much more artificial light out during the night were far more likely to find the disorder. The findings have been based on the Nurses’ Health Study, which followed 109,672 nurses between 1989 and 2013.

large breast cancerBoston, MA — Women who live in areas with higher levels of outdoor light at night may be at higher risk for breast cancer than those living in areas with lower levels, according to a large long-term study from Harvard T.H. Chan School of Public Health. The link was stronger among women who worked night shifts.

he study will be published online August 17, 2017 in Environmental Health Perspectives.

“In our modern day, artificial lighting is almost ubiquitous. Our results imply that this widespread exposure to outside lights during night hours may represent a new risk factor for breast cancer,” said lead author Peter James, assistant professor at Harvard Medical School’s Department of Population Medicine at Harvard Pilgrim Health Care Institute, who did the work while a research fellow in the Departments of Epidemiology and Environmental Health at Harvard Chan School.

Previous studies have suggested that exposure to light at night may lead to decreased levels of the hormone melatonin, which can disrupt circadian rhythms–our internal “clocks” that govern sleepiness and alertness–and, in turn, lead to increased breast cancer risk.

The new study, the most comprehensive to date to examine possible links between outdoor light at night and breast cancer, looked at data from nearly 110,000 women enrolled in the Nurses’ Health Study II in 1989-2013. The investigators linked information from satellite pictures of Earth taken at night to residential addresses for every study participant, and also considered the effect of night shift work. The analysis also factored in detailed info on a number of health and socioeconomic variables among participants.

Girls exposed to the greatest levels of outside light at nighttime–people in the upper fifth–had an estimated 14 percent heightened risk of breast cancer during the study period, when compared with girls in the lowest fifth of vulnerability, the researchers discovered. As amounts of outside light at nighttime improved, so did breast cancer prices.

The association between outside light during the night and breast cancer has been found only among women who were premenopausal and people who were present or previous smokers. Furthermore, the connection was stronger among women who worked night shifts, indicating that exposure to light during the night and night shift work contribute together to breast cancer risk, possibly through mechanisms between cognitive disturbance. The authors acknowledged that additional work is needed to verify the research findings and explain possible mechanics.


Additional Harvard Chan school study writers contained Jaime Hart, Eva Schernhammer, Rulla Tamimi, and senior writer Francine Laden.

Support for the study came in the Harvard NHLBI Cardiovascular Epidemiology Training Grant T32 HL 098048, NIH National Cancer Institute Grant K99 CA201542, NIH Grant UM1 CA176726, and a grant from the Susan G. Komen for the Cure company (IIR13264020).

“Outdoor Light at Night and Breast Cancer Incidence in the Nurses’ Health Study II,” Peter James, Kimberly A. Bertrand, Jaime E. Hart, Eva Schernhammer, Rulla M. Tamimi, Francine Laden, Environmental Health Perspectives, August 17, 2017, doi: 10.1289/EHP935

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Harvard T.H. Chan School of Public Health brings together committed specialists from a number of areas to teach new generations of international health leaders and create strong ideas that enhance the health and lives of people everywhere. As a community of top scientists, teachers, and students, we work together to take revolutionary ideas from the lab to people’s lives–not just making technological discoveries, but also working to transform human behaviors, public policies, and healthcare practices. Annually, over 400 faculty members in Harvard Chan School instruct 1,000-plus full-time pupils from all over the globe and train tens of thousands more through executive and online education classes. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is known as America’s earliest specialist training program in public health.

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