Light During Sleep – Effects on Sleep Quality

Light During Sleep – Effects on Sleep Quality

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We all know the difference a good night's sleep can make and how it feels when we don’t get one. Without realizing it, there are many factors that can affect the quality of our sleep and things we can do to help support it.

According to Northwestern Medicine researchers, moderate lighting during nighttime sleep, or up to two hours before bed, compared to a dimly lit room adversely impacts cardiovascular function during sleep and increases insulin resistance the next day. [1]

Director of the Center for Sleep Medicine at the University, Dr. Zee, tested 20 adults in their twenties by having them spend two nights in a sleep lab, one in a moderately lit room, and one in a dimly lit room. 

Participants were all connected to devices that monitored a number of objective measures of sleep quality, including brain waves, to determine the sleep stage the individual was in, among other things.

In the study, moderate room lighting during sleep impaired glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes, and metabolic syndrome.

The Results

To summarize, you should avoid light exposure, when possible, while sleeping. The study exposed the fact that excessive light may increase the risk for disease by disturbing the nervous system and basic metabolic functions. 

  • Heart rate was increased in participants with the dimmed light, meaning overall cortisol levels were higher. 
  • Heart rate variability was decreased in participants with dimmed light.
  • Blood pressure was significantly increased in individuals that slept under dim light. 
  • Insulin resistance rose among those sleeping under the dim light, meaning their blood sugars would rise and could result in weight gain over time.
  • Melatonin levels were not changed, Dr. Zee says, “because of the insufficient light she placed in the room.” She believes, however, that this hormone would have been affected as well, disrupting the body's natural circadian rhythm.

How Can You Improve Sleep?

There are many things you can do that may improve your sleep. Here are a few tips: 

  • Draw the blinds
  • Dim lights 1-2 hours before bed
  • Try blackout curtains
  • Use an eye mask
  • Keep night lights at floor level
  • Keep white and blue light out of the bedroom

Yes, the type of light you’re exposed to in the evening also makes a difference in your sleep cycle. Studies show that white and blue light put you at higher risk for poor sleep due to their higher energy. [2]

How Joovv Can Help

When the sun goes down in the evening, it is important to pay attention to the type of light we are exposed to. Using red light at night, while avoiding blue light, can help the transition into sleep, which in turn, can improve the quality of our sleep. This is why we created the Ambient Mode feature, to allow access to light without disrupting sleep or circadian rhythms. Learn more about Ambient Mode

We are frequently asked if it is okay to treat with a Joovv in the evening. When it comes to using the treatment modes in a Joovv device, as everyone may respond differently, we suggest listening to your body to decide when the best time for treatment is for you.


Our bodies respond to light, especially at night, and while you might not notice the effects right away, it is important to understand the long-term impact. Health is a lifelong investment, so taking care of your sleep habits now is one way to help bring balance and improve longevity. 

To learn more about sleep and how it impacts our health click here