For more than a year now we have been advising readers that blue light (the shorter wavelength light that shines from our digital devices) interferes with sleep patterns. In the June 19 issue of WebMD, there is more bad news for late-night, in-the-bed users who are bathed in blue light. The article discusses the concerns of Charles Czeisler, chief of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital in Boston.
The bad news is that emerging research suggests that excess artificial light affects not just our sleep, but our overall health. In fact, Dr Czeisler is one of a growing number of experts advising that dark nights are as important as a healthy diet, regular exercise, and good sleep to maintaining a healthy life.
In these days of ‘alternative facts’, some may be tempted to dismiss these warnings. But before you do, consider that NASA has already changed all the lights in the International Space Station to longer wavelength bulbs that dim gradually as night falls. Additionally, the American Medical Association expressed their concern that LED lamps used in streetlights may be contributing to chronic illness.
At the US National Toxicology convention last year, experts presented study after study that suggests a correlation between artificial light at night not just on sleep, but on weight gain, depression, cancer, and heart disease. Pretty sobering stuff from some pretty smart people from very different backgrounds. It might be worth heeding their advice, especially since the solution (sleep in the dark) takes so little effort.
So, what is it about bright, artificial light? As it turns out, light is the most important element in maintaining our daily body rhythms – what scientists call circadian rhythms. As the sun sets, our brains release melatonin and our bodies shift into night mode. Our body temperature drops, hunger decreases, and we get sleepy.
At dawn, the sky gradually turns from black to blue and our brains stop releasing melatonin and instead produce cortisol and ghrelin that increase alertness, hunger, and determination. We are ready to begin another day, or at least we should be ready. If you’re not, it may be the light you’re exposed to.
If the expert opinion doesn’t convince you, consider some research findings. In one such study, exposure to blue light reduced melatonin levels by 55 per cent and participants reported feeling more drowsy the next day. In teenagers, an hour of blue light exposure resulted in a 23 per cent reduction in melatonin release and a two-hour exposure led to a 38 per cent reduction.
And it’s not just sleep that is adversely affected. Exposure to blue light makes you hungrier (remember, melatonin release reduces your hunger) and it causes us to produce less insulin. With less insulin, we don’t burn the calories so we store them in the blood (increasing our risk for diabetes) or we store them as fat.
And here is more bad news. Because melatonin is an anti-cancer agent, fewer melatonin results in an increased risk of cancer. One study conducted by researchers at the Tulane University Center for Circadian Biology found that female night shift workers were 50% to 70% more likely to develop breast cancer. A similar study of nurses found that those who worked the night shift for more than five years were 11 per cent more likely to die early.
In addition to reducing blue light at night, experts recommend that we increase the time we spend in bright light exposure during the day and to that we decrease our exposure to bright lights and blue light, especially in the evening hours as part of our preparation for sleep.
Image credit: Freepik
Dr Richard Marshall is the co-host Psychreg Podcast and is an editorial board member of Psychreg Journal of Psychology.