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  • Writer's pictureSleep Well Blog

Red Light and Sleep

Updated: Jan 30

We know that light is the most important zeitgeber, which is a cue from the environment that influences the regulation of your circadian rhythm and sleep. This means that light plays a significant role in maintaining, advancing, or delaying your internal biological clock.

As you have undoubtedly heard, the introduction of artificial light has played a role in delaying our circadian rhythms and, therefore, the times at which we fall asleep at night. However, do all colours of light influence sleep in the same way?

The answer is no.

Light's colour temperature runs warm and cool. Light on the lower end of that spectrum, as measured in kelvins (K), is considered warm, whereas light at the higher end of the spectrum is considered cool. Exposure to cool, blue light at night can delay your circadian rhythm, such that you fall asleep sleep later than you normally would. Other kinds of light, even warmer, cosier light, can also delay your circadian rhythm. One study actually found that yellow light could potentially exert more influence on circadian entrainment than blue light does, although that study was conducted on mice.

However, research into the effects of red light on sleep indicates promise in terms of supporting sleep quality and reducing sleep inertia, which is the grogginess that you feel upon waking. Prayag, Münch, Aeschbach, Chellappa, and Gronfier (2019) state:

More recently, it was also demonstrated in humans that filtering shorter wavelengths of light [65] or using orange/red light exposure [54,66] in the evening increased sleep duration [54,65], sleep propensity [66], without suppressing melatonin [54,65], as shown by several studies in humans including those with new approaches of spectral tuning [58] and metameric light [101].

Based on the research of Claude Gronfier, PhD, Helight Sleep was developed to support sleep with red light. Greg Bonnier, Vice President of Helight, explains that the red light used for Helight Sleep is 630 nm, which is also the same wavelength that was used in research that investigated the effect of red light on sleep inertia (curious about how nanometers and kelvin are related, click here). Helight Sleep is designed for use at bedtime and automatically turns off after 30 minutes, which is aligned with good sleep hygiene.

While the use of red light for improved sleep quality is promising, more research is needed to explore and understand how red light and sleep are related. Using red light, however, is a safe non-pharmaceutical method for supporting good sleep and may very well be something that you might want to add to your sleep routine!

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