Sleep quality

GOOD FOR SLEEP QUALITY

Deeper nights and clearer mornings – with the right light.

One in three adults in Germany sleeps poorly.*

* Robert Koch Institute: 35.3% of 18- to 79-year-olds report difficulty falling asleep or staying asleep (RKI panel). In the previous survey, DEGS1, the figure was 30.3%

What the right light can change

01 · Melatonin release is supported

The second pillar concerns how we take in light through our eyes after sunset. While artificial blue light from screens and LEDs can suppress the sleep hormone melatonin, the brain needs a clear signal in the evening that night is approaching.

Warm, monochromatic red light (630–670 nm) is key here: because the retina barely responds to this part of the spectrum, it mimics a natural sunset and does not get in the way of melatonin release.

At the same time, red light can support a noticeable sense of recovery:

•⁠ ⁠Easing the nervous system: the body can shift from stress mode (sympathetic) into recovery mode (parasympathetic).
•⁠ ⁠Better recovery: the widening of blood vessels (vasodilation) supports circulation and the supply to your cells overnight.
•⁠ ⁠Mental wind-down: the release of endorphins helps you leave the stress of the day behind.

02 · The neural light filter in the evening and at night (red light)

Blue light at 460-480 nm tells the brain “It’s daytime” and dampens melatonin release (Brainard et al., 2001; Chang et al., 2015). Red light at 630-670 nm barely engages the same receptors. That way you can see enough without disturbing your body clock – even at three in the morning on the way to the bathroom.

→ You keep your bearings without interrupting your night-time rhythm.

03 · Protecting your sleep environment at night

This neurobiological protection also applies during the night: if you get up and switch on the harsh hallway, bathroom or smartphone light, you reactivate the ipRGCs and send an abrupt wake-up signal. Gentle, dimmed red light provides orientation in the dark without flooding the room with harsh light. This way you are not torn out of your sleep environment, your melatonin level remains stable and you can easily drift back to sleep after getting up.

45 % better sleep quality
75 % higher melatonin level*

* Zhao J, Tian Y, Nie J, Xu J, Liu D. Red light and the sleep quality and endurance performance of Chinese female basketball players. J Athl Train. 2012 Nov-Dec;47(6):673-8. doi: 10.4085/1062-6050-47.6.08. PMID: 23182016; PMCID: PMC3499892.

How it works

Your body gauges the time of day by light. Nowadays these light signals often no longer match the natural course of the day – indoors it's relatively dark during the day and often very bright in the evening.

Near-infrared during the day

Most people know melatonin as the sleep hormone. But most of it is actually produced during the day in the cells, linked to near-infrared light. This melatonin doesn't make you tired. It stays in the cell and protects it. Yet window glass and LED lamps filter out almost all of this spectrum.

The right light in the evening

Your retina contains cells that tell the brain what time of day it is. They react strongly to blue light and hardly at all to red. That's why red light can be on in the evening while influencing your internal clock much less than blue light does.

What studies show

Research so far has mainly examined how light affects sleep quality, melatonin levels and recovery markers. The results show a similar pattern: people who are exposed to less activating light in the evening sleep better in the measurements. The studies involved small groups and devices other than ours.

Sleep quality improved by 4.6 points on the PSQI (30 adults, sham-controlled)
Daytime sleepiness reduced by 4.1 points (30 adults, sham-controlled)
Better sleep scores were associated with higher night-time melatonin levels (20
female participants, 14 days of evening red light)
Lower night-time heart rate after full-body sessions (female athletes,
full-body panel)

Sources:
Mehdizadeh, S., et al. (2025). Transcranial photobiomodulation improves sleep quality, reduces daytime sleepiness, and modulates delta power in chronic insomnia.

Zhao, J., Tian, Y., Nie, J., Xu, J., & Liu, D. (2012). Red light and the sleep quality and endurance performance of Chinese female basketball players. Journal of Athletic Training, 47(6), 673–678.

Rentz, L. E., Bryner, R. W., Ramadan, J., Rezaei, S., Galster, S. M., & Hardy, P. (2022). Full-body photobiomodulation therapy is associated with reduced sleep durations and augmented cardiorespiratory indicators of recovery. Sports, 10(9), 134.

Chang, A.-M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112(4), 1232–1237.

Tan, D.-X., Manchester, L. C., Liu, X., Rosales-Corral, S. A., Acuna-Castroviejo, D., & Reiter, R. J. (2013). Mitochondria and chloroplasts as the original sites of melatonin synthesis: a hypothesis related to melatonin's primary function and evolution in eukaryotes. Journal of Pineal Research, 54(2), 127–138.

Zimmerman, S., & Reiter, R. J. (2019). Melatonin and the optics of the human body. Melatonin Research, 2(1), 138–160. Berson, D. M., Dunn, F. A., & Takao, M. (2002). Phototransduction by retinal ganglion cells that set the circadian clock. Science, 295(5557), 1070–1073.

Brainard, G. C., Hanifin, J. P., Greeson, J. M., Byrne, B., Glickman, G., Gerner, E., & Rollag, M. D. (2001). Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. The Journal of Neuroscience, 21(16), 6405–6412.

Commission Internationale de l'Éclairage (2018). CIE S 026/E:2018 — System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light.

Which heilys® is right for you?

£139.00

For the hours after sunset. Red Mode for the last hour and the night. FlameWhite Mode for reading and finding your way. Cordless, dimmable, quiet — bedside table, children's room, hallway.

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£159.00

One device, two times of day. In the evening, pointed at a wall or ceiling as calm, indirect room lighting. During the day, the red and near-infrared spectrum for your daily routine.

View product

£929.00

For a light routine throughout the day. Six wavelengths, each individually dimmable. In the evening, a pure NIR spectrum with no visible activating stimulus.

View product

Near-infrared during the day

Red and near-infrared light on bare skin, ideally in the morning. This is your answer to the spectrum that window glass and LED lamps filter out of your day indoors.

Gen panel · 10–20 min · 15–60 cm

Go to Gen200

In the evening: dial down the light

From about 30 to 90 minutes before bed: ceiling light off, Red Mode on. For reading, the bedtime story, stretching or simply doing nothing.

Go to Gen30

At night: orientation without a wake-up call

On the bedside table, in the hallway, in the children's room. When you get up, while breastfeeding or when you want to
wind down. You can find your way without fully waking yourself up with bright light.

Go to CleanSleep

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45 % better sleep quality 75 % higher melatonin level*

Which heilys® is right for you?

Near-infrared during the day

In the evening: dial down the light

At night: orientation without a wake-up call

Customer Reviews

What doctors & therapists say about heilys®

Prof. Dr. Ottaviano Tapparo

Dr. med. Luise Weinrich

Dr. med. Katharina Broos

Martina & Gerda Kastner

Angela Schröer

Thomas Hartl

Julian Mai

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Frequently asked questions – FAQ

Knowledge, studies & new insights

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45 % better sleep quality
75 % higher melatonin level*