What is blue light and how does it affect you?
Light of all kinds is produced in wavelengths and measured in nanometers. It starts in ultraviolet light, with the shortest wavelengths, runs through the visible spectrum of light and into infrared. As in the rainbow, blue light comes after ultraviolet and has the shortest wavelength of visible light. It is produced naturally by the sun and artificially by electronic light.
Exposure to blue light at night time mimics the effect of the sun and tricks the body into thinking it should still be awake. It stops the production of melatonin, the hormone that makes us feel sleepy and regulates our circadian rhythm.
Sleep and the circadian rhythm
Often described as our “body clock” our natural sleep cycles are regulated by the sun via the production of the hormone melatonin. While sleep cycles do vary slightly between individuals they remain close to the 24-hour cycle and historically have been regulated by the sun. This effect can also be seen in modern times by jet lag and the readjustment of sleeping hours to a new time zone.
When the use of devices producing blue light causes the body to believe it is still daytime the sleep hormone melatonin is not produced and the circadian rhythm is disrupted. This results in it being hard to get to sleep and a poorer quality of sleep when we do.
What happens when our circadian rhythm is disrupted?
A good night’s sleep doesn’t just stop us from feeling tired the next day – it is essential for our health. Being severed from natural rhythms has been found to put people at greater risk of diabetes, obesity, depression, cancer and heart disease.
These ill effects can be especially harmful to the developing bodies of teenagers, who need more sleep than an adult.
What sort of exposure are we talking about?
Laptops, tablets and mobile phones produce blue light and just half an hour's use before bed has been shown to delay good REM sleep by a corresponding thirty minutes. Using these devices before bed to wind down or relax can send a very different message to your brain, resulting in you staying awake longer and disrupting your natural circadian rhythms leading to a host of health issues.
The brightness of these screens and their close range of use increase their effect further over other sources of artificial light.
The scientific evidence on blue light, melatonin and circadian rhythm
The links between melatonin production and the circadian rhythm have been proven since the 1950s and new studies are often published showing the effects of blue light on melatonin and the circadian rhythm. The health risks of disruption to the circadian rhythm are also well documented.
Many of those studies and reports have been summarised below, with links to the originals or further information.
Synchonised circadian rhythms are important to health and wellbeing and their disruption can cause diabetes, depression and obesity and in extreme cases cardiovascular diseases and cancer. [Link: Read this study]
Light at night throws off the circadian rhythm, especially light from screens and energy-efficient lightbulbs with blue light being the most disruptive. [Link: Read this study]
Trouble sleeping linked to tablet or laptop use before bed in this study showing two hours of use at full brightness inhibits melatonin production. [Link: Read this study]
Exposure to light at night time, particularly blue wavelength light, wreaks havoc with the circadian rhythm which can lead to cancer, diabetes, depression and heart disease. [Link: Read this study]
In the press...
Polls show parents estimate their teenagers are getting two hours less sleep than the recommended amount and the negative effects of sleep deprivation in teenagers on school grades and attendance. In adults two hours using blue-light devices before bed hampered melatonin release, affecting circadian rhythms. [Link: Read this story]
Research shows that exposure to blue light increases alertness, decreases feelings of fatigue and boosts brain performance. [Link: Read this story]
With the advent of electricity circadian rhythms began to be influenced by exposure to electric light. [Link: Read this story]
Shorter wavelength blue light has a greater effect on the body than red, and those effects include sleep, gastrointestinal, mood and cardiovascular diseases. [Link: Read this story]
The science is clear on the links between blue light from devices such as mobile phones and the health risks of a disrupted circadian rhythm.