A new European study, led by the Barcelona Institute for Global Health (ISGlobal), has linked nocturnal exposure to blue light with an increased risk of breast and prostate cancer.
The natural light spectrum consists of a set of wavelengths corresponding to colors. The potential danger of blue light (wavelengths between 380 and 500 nm) comes from the shortest wavelengths (perceived as blue-violet). Present in natural light, this light is also abundantly produced by the screens of our gadgets like computers, tablets and smartphones as well as by some LED lighting systems.
An international team led by the Barcelona Institute for Global Health (ISGlobal) conducted a research using data from 4,000 people aged 20 to 85, living in 11 regions of Spain, with or without cancer of the breast and of the prostate.
The researchers evaluated their exposure to indoor artificial light through questionnaires and exposure to artificial night light from Madrid and Barcelona using images taken from the International Space Station. The results show that in both cities, those who were exposed to a greater amount of blue light faced a higher risk — between 1.5 to 2 times higher — of developing breast or prostate cancer, than those who were less exposed.
Manolis Kogevinas, coordinator of the study, comments: “The International Agency for Research on Cancer of the UN World Health Organization has classified night work as probably carcinogenic to humans.” There are proven associations between nighttime artificial light exposure, disruption of the circadian rhythm, and breast and prostate cancers. Throughout this study, we investigated whether it was the nocturnal exposure to the light of the cities that affected the development of these two types of cancer “.
“Because of the ubiquity of artificial light at night, whether or not it increases the risk of cancer is a public health issue,” says Ariadna García-Saenz, author of the study. “At this stage, more in-depth studies need to include more individual information, for example, by sensors that measure indoor lighting, and it would be particularly interesting to study young people who are very exposed to the blue light of screens.”
So far, research has focused on the effect of blue light on sleep. Numerous studies have shown that the growing use of smartphones and tablets at night is fueling a global sleep crisis. In fact, the blue light produced by the screens, decreases the production of melatonin, the hormone regulating sleep.
Many experts therefore recommend to avoid exposure to this light at least two hours before going to bed.