The researchers at the Barcelona Institute for Global Health reviewed data from over 4,000 persons aged 20 to 85 from 11 different Spanish regions, all without breast or prostate cancer. They assessed exposure to artificial light both indoors and outdoors using questionnaires and nocturnal images taken by astronauts on the International Space Station.
The results revealed that those with the highest exposure to blue light had a greater risk of developing breast cancer or prostate cancer compared to those with less exposure to blue light.
Study coordinator Manolis Kogevinas explained, “WHO’s International Agency for Research on Cancer (IARC) has classified night shift work as probably carcinogenic to humans. There is evidence pointing to an association between exposure to artificial light at night, disruption of the circadian rhythm, and breast and prostate cancers. With this study, we sought to determine whether night exposure to light in cities can affect the development of these two types of cancer.”
First author Ariadna García-Saenz added, “Given the ubiquity of artificial light at night, determining whether it increases or not the risk of cancer is a public health issue. At this point, further studies should include more individual data using for instance light sensors that allow measuring indoor light levels. It would also be important to do this kind of research in young people that extensively use blue light emitting screens.”
Several studies have suggested that blue light is harmful to sleep, with some research suggesting that blue light exposure may be an underlying cause for the global sleep epidemic. This is because when exposed to blue light, melatonin is suppressed, preventing us from sleeping.
Many experts suggest reducing or avoiding exposure to blue light prior to bed so you can sleep well, but with the latest research findings, it may also be a wise idea to reduce your exposure to blue light as a means to reduce your risk of breast cancer or prostate cancer.
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