Study Showed Relationship to Nighttime Blue Light Exposure and Cancer: Circadian Rhythm Is Important to Health

An interesting study done in 2018 by the Barcelona Institute for Global Health showed a relationship between exposure to blue light at night time and breast and prostate cancer. Exposure includes night shift workers and people who have an upset in the circadian rhythm by working at night or by being exposed to artificial light at night. The researchers studied 11 Spanish regions over a 5 year period taking data from over 4,000 people. Exposure to outdoor light at night was associated with both breast cancer and prostate cancer, and that men who slept in illuminated bedrooms had an increase in prostate cancers.

The findings of the artificial light at night study :

Findings from this large case–control study of two cancers that have been associated with circadian disruption and light at night during shift work provide some support for the influence of ALAN for the development of cancer in the general population. Men who reported the highest level of exposure to indoor ALAN were at greater risk of prostate cancer than men who reported no indoor illumination at night. Although both cancers were less likely among those in the highest versus lowest tertile of exposure to outdoor ALAN in the visible spectrum, outdoor ALAN in the blue-light spectrum, which is believed to be the most biologically relevant exposure, was positively associated with prostate cancer and, to a lesser extent, with breast cancer.

The body’s internal clock is important and if the sleep clock is off it can have negative effects. In a 2013 bulletin from the World Health Organization, it was noted that there has been an increase in breast cancer in richer nations than poorer ones. Richer countries seemed to have many factors in common resulting in higher breast cancers including obesity, increased alcohol use, an older childbearing age and a reduction in breast feeding time, and chemicals in the environment. But, a circadian disruption and exposure to blue light seemed to have the highest factor of causing breast cancer.

“There is stronger evidence for shift work involving circadian disruption as a factor for developing breast cancer than for chemicals,” Straif of IARC [International Agency for Research on Cancer] says. Shift work involving disruption of normal sleep routines is currently classified as an “IARC 2A carcinogen,” he adds, which means that it is probably carcinogenic to humans.

What is the Circadian Rhythm?

The circadian rhythm is the body’s 24-hour cycle, and the sleep-awake cycle is one of the most important ones. It has an influence on DNA repair, metabolism regulation, and mental health and well-being. Good sleep hygiene leads to quality, and consistently uninterrupted, sleep. And good sleep leads to better overall health.

In a recently updated Harvard Health Letter, Harvard researchers found through sleep experiments that blue light suppressed melatonin for twice as long as green light, and that it shifted circadian rhythms. Another study, conducted by the University of Toronto, showed that blue light is a melatonin suppressor, and that perhaps blocking blue light could help shiftworkers and people who did computer work late into the night.

Although it is environmentally friendly, blue light can affect your sleep and potentially cause disease.

At night, light throws the body’s biological clock—the circadian rhythm—out of whack.
 
Exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms. Even dim light can interfere with a person’s circadian rhythm and melatonin secretion.

What is Blue Light and How to Reduce Exposure?

Blue light rays are short, invisible, high energy wavelengths, and they come from LED televisions, computer monitors, fluorescent lights, and smart phones and tablets. According to the University of Wisconsin-Madison IT campus, ways to protect yourself from blue light include reducing screen time, using blue light filters for your computer screens and smart phones, and wearing yellow tinted computer glasses.

Sources:

Garcia-Saenz, Ariadna et al. “Evaluating The Association Between Artificial Light-At-Night Exposure And Breast And Prostate Cancer Risk In Spain (MCC-Spain Study)”. Environmental Health Perspectives, vol 126, no. 4, 2018, p. 047011. Environmental Health Perspectives, doi:10.1289/ehp1837. Accessed 26 Aug 2020.

Geiger, Erik. “How To Protect Your Eyes From The Harm Of Blue LED Light – UW–⁠Madison Information Technology”. UW–⁠Madison Information Technology, 2017, https://it.wisc.edu/news/protect-eyes-harmful-effects-blue-led-light/. Accessed 26 Aug 2020.

Harvard Healthy Publishing. “Blue Light Has A Dark Side – Harvard Health”. Harvard Health, 2012, https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side. Accessed 26 Aug 2020.

“The Breast Cancer Conundrum”. Vol 91, no. 9, 2013, pp. 626-627. WHO Press, doi:10.2471/blt.13.020913. Accessed 26 Aug 2020.