Exposure to Mobile Phone Light at Night Increases Risk of Colorectal Cancer

Night-time exposure to artificial light, especially blue light may raise the risk of colorectal cancer, reports a new study. The findings of the study are published in the journal Epidemiology. Previous studies have found associations between night-time exposure to artificial light--especially blue light--and various adverse health effects, including sleep disorders, obesity, and increased risk of various types of cancer, especially in night-shift workers. Blue light is a range of the visible light spectrum emitted by most white LEDs and many tablets and phone screens. An earlier study by ISGlobal found a link between exposure to blue light at night and increased risk of breast and prostate cancer.

"Using the same methodology as the previous study, we decided to analyze the relationship between exposure to artificial light and colorectal cancer, the third most common type of cancer worldwide after lung and breast cancer," explained Manolis Kogevinas, Scientific Director of the Severo Ochoa Distinction at ISGlobal and coordinator of the new study.

The World Health Organisation's International Agency for Research on Cancer (IARC) classifies night-shift work as probably carcinogenic to humans; breast, prostate and colorectal cancer are associated with the highest risk.

The authors analyzed data obtained through the MCC-Spain project on approximately 2,000 adults in Barcelona and Madrid, of whom 660 had colorectal cancer, and the rest were randomly selected from the local population. Individuals with a history of working night shifts were excluded. Night-time levels of outdoor artificial light were determined using images from the International Space Station (ISS).

Results from both cities showed that participants with the highest exposures to blue light had a 60% higher risk of developing colorectal cancer than the less-exposed population. No association was found with full-spectrum light.

"Night-time exposure to light, especially blue-spectrum light, can decrease the production and secretion of melatonin, depending on the intensity and wavelength of the light," explains Kogevinas.

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Because exposure to light was estimated using satellite images, this calculation did not take into account individual behaviors such as the use of rolling shutters, which is common in Spain and other Mediterranean countries. The estimate of exposure can, therefore, be interpreted as the amount of light people are exposed to when they are outside their homes--a common pattern in Spain--and inside their homes before closing the shutters and going to bed.

"There is growing concern about the effects of light on ecosystems and human health," commented Kogevinas. "Research on the potential effects of light exposure is still in its infancy, so more work is needed to provide sound, evidence-based recommendations to prevent adverse outcomes."

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Source-Eurekalert