What is blue light? How it affects sleep and more.
Blue light is environmentally friendly, but it can affect sleep and cause illness. Before the advent of artificial lighting, the sun was the main source of light and people spent the night in (relative) darkness. Now, in many parts of the world, nights are brighter and we almost take for granted that we have easy access to those lumens.
But we may be paying a price for all that light: At night, light can disrupt our body’s internal clock, or circadian rhythm, disrupting our sleep. To make matters worse, research shows: May It contributes to cancer, diabetes, heart disease and obesity.
What is Blue Light?
Not all colors of light are equal. Blue wavelengths are beneficial during the day, boosting alertness, reaction time, and mood, but appear to have the most detrimental effects at night. And the prevalence of electronic devices with screens and energy-efficient lighting increases our exposure to blue wavelengths, especially after the sun goes down.
Light and sleep
Circadian rhythms vary slightly from person to person, but on average they are 24 hours and 15 minutes long. Night owls have slightly longer circadian rhythms, while early risers have rhythms that are less than 24 hours long. Dr. Charles Czeisler of Harvard Medical School showed in 1981 that sunlight synchronizes a person’s internal clock with their environment.
Is nighttime light exposure bad for you?
Some studies suggest a link between exposure to light at night, such as during night shifts, and diabetes, heart disease and obesity. This is not proof that exposure to light at night causes these diseases, nor is it clear why it’s bad for us.
Exposure to light suppresses the production of melatonin, a hormone that influences circadian rhythms. Even dim light can disrupt a person’s circadian rhythm and melatonin production, even at just 8 lux (more bright than most desk lamps and about twice as bright as a nightlight). Light at night is one of the reasons many people don’t get enough sleep, and researchers have found that short sleep increases the risk of depression, diabetes, and cardiovascular disease.
The effects of blue light on sleep
While all types of light suppress melatonin secretion, blue light at night has a stronger effect. Researchers at Harvard University conducted an experiment comparing the effects of 6.5 hours of blue light exposure to similarly bright green light. Blue light suppressed melatonin for nearly twice as long as green light, and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).
In another blue light study, researchers from the University of Toronto compared melatonin levels in people exposed to bright indoor light while wearing blue-light blocking goggles with people exposed to normal dim light without goggles. The fact that the hormone levels in the two groups were similar strengthens the hypothesis that blue light is a strong suppressor of melatonin. It also suggests that shift workers and night owls could conceivably be protected by wearing eyewear that blocks blue light. Cheap sunglasses with orange-tinted lenses block blue light, but they also block other colors, making them unsuitable for use indoors at night. Glasses that block only blue light can cost up to $80.
LED Blue Light Exposure
If blue light has adverse health effects, environmental concerns and the pursuit of energy-efficient lighting may be at odds with personal health. Spiral compact fluorescent and LED lights are far more energy efficient than the old-fashioned incandescent bulbs we grew up with, but they also tend to emit more blue light.
While the physics of fluorescent light cannot be changed, the coating inside the bulb can be altered to make it emit a warmer, less blue light. LED lights are more efficient than fluorescent lights, but they also emit a fair amount of light in the blue spectrum. Ordinary incandescent light bulbs also emit some blue light, although not as much as most fluorescent lights, says Richard Hansler, a light researcher at John Carroll University in Cleveland.
Protect yourself from blue light at night
- Use dim red light for nighttime lighting, as red light is less likely to shift your circadian rhythm or suppress melatonin.
- Avoid looking at bright screens for two to three hours before bedtime.
- If you work the night shift or frequently use electronic devices at night, consider wearing blue light blocking glasses or installing an app that filters out blue/green wavelengths at night.
- Getting plenty of bright light during the day can improve your ability to sleep at night and also improve your mood and alertness during the day.
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