Cancer Research Flash outdoor lighting increases breast cancer risk in women

Is there a connection between nocturnal outdoor lighting and breast cancer?
There are many environmental factors that affect the risk of developing breast cancer. Researchers have now found that in areas with a higher nighttime concentration of outdoor light, women are at an increased risk for breast cancer compared to women from areas with lower levels of nocturnal outdoor lighting.

The scientists of internationally recognized Harvard T.H. Chan's School of Public Health found in their study that an increased concentration of outdoor lighting at night leads to an increased risk of breast cancer in women. This connection was even stronger when women worked on the night shift. The physicians published the results of their study in the journal "Environmental Health Perspectives".

Physicians found that nighttime outdoor lighting can have a significant impact on women's risk of developing breast cancer. (Image: Haz / fotolia.com)

Outdoor lighting during the night Risk factor for the development of breast cancer
In our modern industrialized society, artificial lighting is almost overpresent. The widespread exposure to outdoor lighting during the night could be a new risk factor for breast cancer, says author Professor Peter James of the Harvard Pilgrim Health Care Institute.

Nocturnal outdoor lighting affects our internal clock
So far, the results of studies have suggested that exposure to light at night may result in a decreased level of the hormone melatonin. This effect can disrupt the so-called circadian rhythms, which are also referred to as our internal clock, the researchers say. Our internal clock influences our fatigue and general alertness, which in turn can increase the risk of developing breast cancer.

Scientists analyze the data of nearly 110,000 women for their study
The new study was the most comprehensive study yet of possible connections between outside light at night and breast cancer, say the authors. For this purpose, the physicians looked at the data of almost 110,000 women, which were part of the so-called Nurses' Health Study II, which took place between the year 1989 and the year 2013.

Researchers use nocturnal satellite images of participants' homes
For their investigation, the researchers linked the data with the records of satellite images of the Earth, which were taken at night at the residential addresses of study participants. The experts also examined the influence of shift work at night. The study also included detailed information on a variety of health and socioeconomic factors among participants, the authors explain.

Increased breast cancer risk was about 14 percent in some women
Among the women exposed to the highest concentration of outdoor light during the night, there was an approximately 14 percent increased risk of developing breast cancer during the study period compared to women in the lower fifth of exposure to nocturnal outdoor light the authors in a press release of Harvard TH Chan School of Public Health. The results clearly show that as the concentration of outdoor light increases at night, the rates of breast cancer also increase, the researchers explain. (As)