The Blue Light - New Study Reveals Both the Detriments AND Benefits of Our Electronic Devices
Jarod Kintz, in his book This Book Title is Invisible, issued the following wisdom: "Reading - it's the third best thing to do in bed."
While I would agree with this sentiment, I might argue that reading is a close third, given the popularity of devices such as the ipad, Nook and Kindle. As a doctor, I have seen the results of this popularity, inviting these back-lit devices into bed in the pre-sleep portion of the day.
Unfortunately, that light exposure is having some troubling effects on our sleep quality.
The Rhythm of the Night
Our bodies are guided by circadian rhythms that tell us essentially that the daytime is wakeful and the nighttime is sleepful. The physical, mental and behavioral changes that occur through a 24 hour cycle are the essence of the circadian rhythm. This rhythm is felt to be regulated by our body's "master clock," an area deep in the brain called the suprachiasmatic nucleus (SCN).
Besides the sleeping and waking cycles, circadian rhythms can influence the release of various hormones and help to regulate body temperature. The most important hormone in this system is melatonin which is released by the nerve cells of the SCN. The drive for this system seems to be exposure (or lack of) to sunlight. The presence of artificial light in our environment after the sun goes down confuses this balanced circadian rhythm.
Lights are Not Created Equal
Sunlight is known as white light. It contains all of the wavelengths or rainbow of colors in the spectrum. When different concentrations of wavelength predominate in light, it has a hue or color. Things that glow from heat tend to have greater concentrations of the red-orange spectrum of colors. This is appreciated as a warm glow as observed in the old-fashioned fire in the fireplace, the flicker of a candle or the glowing wire filament of a light bulb.
In recent times, however, our evenings are illuminated more so by television screens, ipads, reading devices and energy-efficient LED lights. These newer light sources emit higher concentrations of light in the blue wavelength spectrum. (You may have noticed the difference while driving at night where common headlights have a yellow-orange hue and then newer LED headlights have a bright white-blue hue.)
Scientific studies have now shown a significant difference as to how these different light sources affect our body. Exposure to night-time blue wavelength light has been linked to lower secretion of melatonin in the body.
What Does This Mean?
Lower levels of melatonin means disordered circadian rhythm. This, in-turn, leads to disordered sleep with more alertness in the evening and more tiredness during the day. Disordered melatonin has also been linked to diabetes, heart disease and obesity. There is also some quite preliminary evidence that this disorder could also increase the risk for various types of cancer. In addition, poor sleep has been linked to disordered mood, namely depression.
Is Blue Light All Bad?
While blue light at night generally garnered a negative impact on the body, some benefits of these findings have been realized. Exposure to subjects in studies revealed increased alertness based on testing and brainwave testing. While not helpful every night, there are times when alertness is necessary at the expense of sleep such as with driving or learning material.These benefits are likely episodic and short-lived, however. This alertness followed through when exposure and testing were performed during the daytime hours.
Putting Knowledge to Practice
1. Reduce LED light exposure at night, favoring less bright incandescent light
2. Try to reduce exposure to back-lit monitors found on televisions, computers, cell-phones and reading devices within two hours of sleep
3. Favor LED light exposure during the day to enhance alertness