Binary numbers code of computer monitor reflect to her eyeglasses.


Binary numbers code of computer monitor reflect to her eyeglasses.

Photo by: Yuichiro Chino

Yuichiro Chino

Can Blue Light Really Mess Up Your Sleep?

By: Robin Fearon

We are spending more time looking at screens than ever, and those screens emit blue light. What is "blue light" and what does it do to your sleep cycle?

May 06, 2020

Sleep plays a vital part in repairing the body and keeping us healthy, but getting a good night's sleep with all of the demands of modern living can be a challenge. Computer and smartphone use have been identified as a source of disturbance because of the blue light emitted by their LED displays. Yet, new research says screen time alone may not be as detrimental as we think.

Colored Light and Sleep

Scientists at the University of Manchester assessed the impact of colored light on the sleep patterns of mice to learn more about how different colours act on the body. They noted that twilight – dimmer and bluer light than normal daylight – provides a physical signal about when to sleep. So, using brighter, warmer lights in the day and dimmer, cooler lights in the evening could be better for our health.

Earlier studies have found that blue light exposure at night decreases the hormone melatonin and interferes with circadian rhythms that regulate our sleep-wake cycles. This early conclusion Using LED screens that emit a lot of excitatory blue light can disrupt sleep.

The researchers expected to disrupt the circadian cycle in this experiment because of a photopigment in the eye called melanopsin. This light sensitive protein is found in the retinal ganglion cells of mammals. Melanopsin helps set the body's circadian rhythms and is particularly sensitive to blue light.

What the Manchester group did to test different light wavelengths was to use lighting that changed color without altering brightness. They found that contrary to popular belief, equally bright yellow or white light has a stronger influence on our internal clock than blue light.

Do Night Settings on Tech Help?

Mature woman using laptop while man sleeping on bed at home


Mature woman using laptop while man sleeping on bed at home

Photo by: Portra Images

Portra Images

“There is [a lot] of interest in altering the impact of light on the clock by adjusting the brightness signals detected by melanopsin but current approaches usually do this by changing the ratio of short and long wavelength light; this provides a small difference in brightness at the expense of perceptible changes in color,” said Dr Tim Brown, a senior lecturer at the school of medical sciences and one of the study's authors.

Simply manipulating the amount of blue relative to yellow light may be less important than reducing brightness. Night time settings and blue light filters that 'warm up' PC and smartphone screens by increasing yellow light could actually be counterproductive.

Origins of Blue Light Warnings

The health warnings attached to blue light run deeper than disturbed sleep. Harvard Medical School links exposure to blue light at night to cancer, heart disease, obesity, and diabetes. Though sunlight is the main source of blue light we are exposed to, the way we stare at computers and smartphones for long periods gives cause for concern.

The eye is not good at blocking blue light. Too much exposure has been shown under laboratory conditions to damage light sensitive cells in the retina. It could lead to cataracts in the lens of the eye and dry eyes due to corneal damage. Worse still it could increase the risk of a condition called macular degeneration, that can lead to sight loss.

The worry surrounding the intensity of LED screens is balanced out by advice from Public Health England. John O'Hagan from the centre for radiation, chemical, and environmental hazards says the blue light levels in devices “don't come anywhere near the international exposure limits even for prolonged viewing, and are only a fraction of what you’d get just walking outdoors on a cloudy day.”

Tips for Better Sleep and Eye Health


Photo by: Tuan Tran

Tuan Tran

Bright lights of any kind will alter the body's clock, he says. So dimming the lights and not staring at bright back-lit screens at least an hour before bed will help regulate sleep better. Preparing for sleep by doing something less stimulating before closing your eyes results in a better night's rest.

And try this for better all-round eye health at work: the 20-20-20 rule from the American Optometric Association. Take a 20 second break from your screen every 20 minutes to look at something 20 feet in the distance. This will break your stare and allow you to refocus and blink at a normal rate again.

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