Several years ago, my colleagues and I conducted a study examining whether blue light-blocking glasses could improve employee sleep and work performance. We found that wearing these glasses in the evening improved sleep, with benefits that extended into the following workday.
But that research left me wondering about the other half of the day. If blocking blue light in the evening improves sleep, what happens if we deliberately increase blue light exposure in the morning? Could that also improve sleep and subsequent performance at work? In a new paper, colleagues and I find that it does.
Our sleep is partially regulated by a biological process known as the circadian rhythm, an approximately 24-hour cycle that helps determine when we feel alert and when we feel sleepy. Although circadian rhythms are generated internally, they are also influenced by environmental cues, especially light. Blue wavelengths of light have particularly powerful effects on this system.
Exposure to blue light late in the evening can delay our circadian rhythms, pushing back the time when our bodies are prepared to sleep. However, exposure in the morning can have the opposite effect, shifting our circadian rhythms earlier and helping synchronize our biological clocks with the external 24-hour day. This can make it easier to fall asleep at an appropriate time later that night.
One way to obtain morning blue light exposure is to spend time outdoors in natural sunlight. That works well in sunny climates with nice weather, but what can people do in adverse conditions or when they simply don’t have time to go outside? An alternative is to use blue light-producing glasses.
What Are Blue Light-Producing Glasses?
Unlike blue light-blocking glasses, which filter incoming blue light, blue light-producing glasses actively emit blue light toward the eyes. They are lightweight wearable glasses with small light sources positioned to direct blue-turquoise light toward the wearer's eyes. The glasses are designed to be worn during ordinary morning activities, allowing people to receive controlled blue light exposure without sitting in front of a light therapy lamp or spending time outdoors.
In a new study accepted for publication in the Journal of Applied Psychology, my colleagues Kathleen Keeler, Yiming Huang, Brian Gunia, Jason Moy, and I examined whether wearing these glasses in the morning could improve sleep and subsequent outcomes at work. For this study, a manufacturer of blue light-producing glasses donated 100 pairs for our research, and our research team purchased another 100 (the manufacturer did not provide any financial support for this study). Although other devices delivering similar light exposure should produce similar benefits, we tested only one manufacturer's glasses.
Testing the Effect of Blue-Light Glasses on Work
We conducted a two-week field experiment involving 182 full-time employees at a large university in the Midwestern United States. Participants were instructed to wear blue light-producing glasses for 30 minutes shortly after waking each workday morning.
However, the glasses did not always emit the same amount of blue light. During one week, they emitted blue light at full intensity. During the other week, they emitted blue light at only 1 percent intensity, serving as our control condition. We randomly assigned participants to experience the full-intensity condition first or the control condition first. Thus, every participant experienced both conditions, allowing us to compare their outcomes across the two weeks. Participants also completed daily surveys assessing their sleep duration and quality, their alertness and cognitive depletion, and several work outcomes, including work engagement, task performance, helping coworkers, and counterproductive work behaviors.
We found that morning blue light exposure increased subsequent sleep duration by approximately 11 minutes per night and improved self-reported sleep quality by approximately 3.5 percent relative to the overall average. Although these improvements were modest, they resulted from just 30 minutes of morning light exposure, without requiring participants to substantially change their routines. This suggests that even relatively small adjustments to our daily light exposure may produce meaningful benefits.
Sleep Essential Reads
These improvements in sleep were associated with important benefits the following day. Employees who slept longer and better subsequently experienced greater alertness. Better sleep quality was also associated with reduced cognitive depletion, meaning employees had more mental resources available to sustain effort, regulate attention, and control their behavior. Greater alertness was associated with higher work engagement and more helping behavior toward coworkers. Reduced cognitive depletion was associated with improvements in work engagement, task performance, and reductions in counterproductive work behavior.
Perhaps the most interesting finding concerns the timing of these effects. One might expect blue light-producing glasses to work like a cup of coffee, immediately increasing alertness and improving performance. However, our supplemental analyses did not find significant immediate effects on alertness, depletion, or work outcomes on the same day as exposure.
Instead, the evidence supported a more delayed process. Employees wore the glasses in the morning, slept longer and better that night, and subsequently experienced psychological benefits that were associated with improved functioning at work the following day. This makes sense given what we know about circadian rhythms. Rather than acting like a stimulant that produces an immediate boost in alertness, the glasses appear to influence sleep by helping regulate the body's internal clock.
We also explored whether certain employees benefited more than others. Employees who already experienced greater sleep difficulties showed stronger improvements in sleep quality. Younger employees also experienced larger improvements in sleep duration, with downstream benefits for work engagement and helping behavior. Age-related changes in sensitivity to light may help explain this pattern, although these exploratory findings require further research.
Implications for Sleep and Work
Our findings suggest that blue light-producing glasses may offer a way to improve sleep, particularly for people who have difficulty obtaining morning sunlight. A brief session could potentially fit into an existing morning routine, without requiring people to substantially change their schedules.
However, it is important to recognize that we did not directly compare the glasses with natural morning sunlight. We therefore cannot conclude that these devices are more effective than simply spending time outdoors after waking. For people who can easily obtain morning sunlight, that sunlight likely has an analogous and perhaps even more powerful effect.
Taken together, my earlier research on blue light-blocking glasses and our new research on blue light-producing glasses suggest that managing light exposure throughout the day may be an important way to improve sleep and work outcomes. Reducing blue light exposure in the evening and increasing it in the morning may provide complementary benefits.
More broadly, this research illustrates how interventions targeting our circadian rhythms can influence our functioning well beyond the time when those interventions occur. A brief change to our morning routine may help us sleep better that night and function more effectively at work the following day. In short, blue light in the morning may elicit more restful nights and more productive days.