Blue-light filtering glasses help improve sleep and work productivity

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During the pandemic, the amount of screen time for many people working and learning from home as well as binge-watching TV has sharply increased.

New research finds that wearing blue-light glasses just before sleeping can lead to a better night’s sleep and contribute to a better day’s work to follow.

“We found that wearing blue-light-filtering glasses is an effective intervention to improve sleep, work engagement, task performance and organizational citizenship behavior, and reduced counterproductive work behavior,” said Cristiano L. Guarana, assistant professor of management and entrepreneurship at the Indiana University Kelley School of Business.

“Wearing blue-light-filtering glasses creates a form of physiologic darkness, thus improving both sleep quantity and quality.”

Most of the technology we commonly use — such as computer screens, smartphones and tablets — emits blue light, which past research has found can disrupt sleep.

Workers have become more dependent on these devices, especially as we navigate remote work and school during the coronavirus pandemic.

The media have recently reported on the benefits of blue-light glasses for those spending a lot of time in front of a computer screen.

This new research extends understanding of the circadian rhythm, a natural, internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours.

“In general, the effects of wearing blue-light-filtering glasses were stronger for ‘night owls’ than for ‘morning larks,’ said Guarana, who previously has studied how lack of sleep affects business decisions, relationships and other behaviors in organizations.

“Owls tend to have sleep periods later in the day, whereas larks tend to have sleep periods early in the day.

“Although most of us can benefit from reducing our exposure to blue light, owl employees seem to benefit more because they encounter greater misalignments between their internal clock and the externally controlled work time. Our model highlights how and when wearing blue-light-filtering glasses can help employees to live and work better.”

The findings appear in the paper, “The Effects of Blue-Light Filtration on Sleep and Work Outcomes,” published online by the Journal of Applied Psychology. Guarana is the corresponding author; his co-authors are Christopher Barnes and Wei Jee Ong of the University of Washington.

The research found that daily engagement and performance of tasks may be related to more underlying biological processes such as the circadian process.

“Our research pushes the chronotype literature to consider the relationship between the timing of circadian processes and employees’ performance,” the researchers wrote.

A good night’s sleep not only benefits workers; it also helps their employers’ bottom lines.

“This study provides evidence of a very cost-effective means of improving employee sleep and work outcomes, and the implied return on investment is gigantic,” said Barnes, professor of management and the Evert McCabe Endowed Fellow at the University of Washington’s Foster School of Business. “I personally do not know of any other interventions that would be that powerful at that low of a cost.”

Across two studies, researcher collected data from 63 company managers and 67 call center representatives at Brazil-based offices for a U.S. multinational financial firm and measured task performance from clients. Participants were randomly chosen to test glasses that filtered blue light or those that were placebo glasses.

“Employees are often required to work early mornings, which may lead to a misalignment between their internal clock and the externally controlled work time,” the researchers said, adding that their analyses showed a general pattern that blue-light filtration can have a cumulative effect on key performance variables, at least in the short term.

“Blue-light exposure should also be of concern to organizations,” Guarana said.

“The ubiquity of the phenomenon suggests that control of blue-light exposure may be a viable first step for organizations to protect the circadian cycles of their employees from disruption.”


What is blue light?

Not all colors of light have the same effect. Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown.

Light and sleep

Everyone has slightly different circadian rhythms, but the average length is 24 and one-quarter hours. The circadian rhythm of people who stay up late is slightly longer, while the rhythms of earlier birds fall short of 24 hours. Dr. Charles Czeisler of Harvard Medical School showed, in 1981, that daylight keeps a person’s internal clock aligned with the environment.

Is nighttime light exposure bad?

Some studies suggest a link between exposure to light at night, such as working the night shift, to diabetes, heart disease, and obesity. That’s not proof that nighttime light exposure causes these conditions; nor is it clear why it could be bad for us.

A Harvard study shed a little bit of light on the possible connection to diabetes and possibly obesity. The researchers put 10 people on a schedule that gradually shifted the timing of their circadian rhythms. Their blood sugar levels increased, throwing them into a prediabetic state, and levels of leptin, a hormone that leaves people feeling full after a meal, went down.

Exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms. Even dim light can interfere with a person’s circadian rhythm and melatonin secretion. A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect, notes Stephen Lockley, a Harvard sleep researcher. Light at night is part of the reason so many people don’t get enough sleep, says Lockley, and researchers have linked short sleep to increased risk for depression, as well as diabetes and cardiovascular problems.

Effects of blue light and sleep

While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness.

The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).

In another study of blue light, researchers at the University of Toronto compared the melatonin levels of people exposed to bright indoor light who were wearing blue-light–blocking goggles to people exposed to regular dim light without wearing goggles.

The fact that the levels of the hormone were about the same in the two groups strengthens the hypothesis that blue light is a potent suppressor of melatonin. It also suggests that shift workers and night owls could perhaps protect themselves if they wore eyewear that blocks blue light.

Inexpensive sunglasses with orange-tinted lenses block blue light, but they also block other colors, so they’re not suitable for use indoors at night. Glasses that block out only blue light can cost up to $80.

LED blue light exposure

If blue light does have adverse health effects, then environmental concerns, and the quest for energy-efficient lighting, could be at odds with personal health. Those curlicue compact fluorescent lightbulbs and LED lights are much more energy-efficient than the old-fashioned incandescent lightbulbs we grew up with. But they also tend to produce more blue light.

The physics of fluorescent lights can’t be changed, but coatings inside the bulbs can be so they produce a warmer, less blue light. LED lights are more efficient than fluorescent lights, but they also produce a fair amount of light in the blue spectrum. Richard Hansler, a light researcher at John Carroll University in Cleveland, notes that ordinary incandescent lights also produce some blue light, although less than most fluorescent lightbulbs.

Protect yourself from blue light at night

  • Use dim red lights for night lights. Red light is less likely to shift circadian rhythm and suppress melatonin.
  • Avoid looking at bright screens beginning two to three hours before bed.
  • If you work a night shift or use a lot of electronic devices at night, consider wearing blue-blocking glasses or installing an app that filters the blue/green wavelength at night.
  • Expose yourself to lots of bright light during the day, which will boost your ability to sleep at night, as well as your mood and alertness during daylight.

Source: Indiana University

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