Optimal light environment and hacks for shift workers

Circadian rhythms regulate the entire functioning of the human body. The natural light-dark cycle is the dominant stimulus for circadian rhythms. Sleep/wake times, food intake, and movement are secondary time cues for circadian rhythms.

Optimizing your light exposure is the foundation for a healthy lifestyle and circadian rhythms, whether you work shifts or not. Shift work throws off your rhythm and your body’s timetable. Your shift schedule is usually out of sync with your natural environment, making it more challenging to get enough healthy light.

To understand the subsequent recommendations regarding ideal light exposure, we need to examine some details about light: its wavelengths or colors, the resulting color temperature, and brightness. 

The visible light spectrum (380 to 780nm) is enveloped by invisible light in the form of ultraviolet light (UV, 280-380nm) on one end and infrared light (IR, 780-3000nm) on the other end. Short-wavelength UV and blue light are activators and stressors, whereas long-wavelength red and IR light are regenerative. About 50% of sunlight is red and IR light, while UV makes up less than 5%.

Each separate frequency or color of sunlight has nutritional value for cells.

– Dr Jack Kruse

Natural light is dynamic and changes its composition constantly. The appearance and intensities of wavelengths build from dawn to solar noon as the sun rises in the sky and then slowly diminish towards dusk. At sunrise, red light is more dominant than blue light, while UV light is absent. UV light appears some time after sunrise and disappears a while before sunset sunrise (see the Circadian App for exactly when this happens at your location). Natural light represents a homeostasis between damage (think UV and blue) and repair (think red and IR). 

Modern artificial lighting breaks the natural balance by being high in the blue spectrum with only a small portion of red, while UV and IR are absent. Artificial light is also static, meaning it tells your master clock in the brain that it is the same time independent of the time of day/night.

spectral comparison

Blue light (400-495nm) sets circadian rhythms via special photoreceptor cells (melanopsin) in your eyes that are linked to the master clock in your brain. Blue light triggers cortisol production and suppresses melatonin. Bright blue light exposure (ideally in the form of a sunrise) is essential in the morning to wake us up. From solar noon onward, blue light wanes. At sunset, blue light starts to disappear, while red and infrared frequencies dominate. The waning blue light is a critical circadian signal that the day turns to night, and the body shifts from activity to rest and repair. Thus, blue light should be avoided after sunset/leading up to bedtime to prevent circadian disruption and ensure deep, restorative sleep.

Color temperature refers to the warmth or coolness of light, measured in Kelvin (K). Light with higher color temperatures, such as cool white (5000K-6500K), mimics natural daylight, signaling to the body that it’s daytime and promoting alertness and activity. On the other hand, lower color temperatures, like warm white (2700K-3000K), emulate morning or evening. The warmer hues of sunrise and sunset are around 2000K, signaling to the body that it’s time to promote relaxation and prepare for sleep. Therefore, exposure to cooler temperatures during the middle of the day and warmer temperatures after waking and toward the end of your day regulate circadian rhythms, promoting better sleep quality and overall well-being.

The brightness of light, as seen by the human eye, can be measured in lux. For comparison purposes, moonlight is about 1 lux, a brightly lit office is about 500 lux, an overcast day is about 2,000 lux, a spring day is about 40,000 – 60,000 lux, and bright summer sunlight can be up to 120,000 lux. This means you cannot get sufficient bright light during the day under artificial light, as indoor light intensities can be 100 to 1,000 fold lower than daylight. In contrast, artificial light at night is way too bright. 

If you do not get your light right, you don’t get your health right.

– Dr Michael Twyman

Thus, we ideally want lots of natural, bright light during the day and minimize exposure to artificial light in the evening to promote healthy circadian rhythms and hormone balance.

So, the ideal light flow from waking to sleeping looks something like this:

Optimal light conditions

This circadian light scenario is obviously limited when doing shift work. The main limitation is the shift away from the natural day-night cycle and accessibility to daylight. This means you will be missing out, partially or entirely, on ultraviolet, red and infrared light. Additionally, the light you are exposed to, for the most part, will not be bright enough, and thus, it will be a weaker circadian signal. At the same time, artificial light will be a subtle but constant trigger for stress hormone production, which is not in your best interest.

To overcome these issues, aim to closely mimic the depicted light conditions by applying some of the following light hacks:

    1. If you wake during daylight hours, step outside for at least 5 minutes and get a good dose of natural light into your eyes (without glasses or contact lenses). This is the most important circadian signal.
    2. If you rise at night, expose your eyes to a warm light source first and avoid cold light for at least 15-30min.
    3. If you are working during daylight hours, take regular light breaks outside if possible. This gives your eyes a break, strengthens your circadian rhythm and will improve your sleep.
    4. Trouble getting going, feeling alert? Look into a bright light source for 10-30min (assuming daylight is unavailable). A full-spectrum lightbox is ideal and would be worth the investment since it contains all wavelengths and has more than 10,000lux. You can also get special glasses for shift workers that shine blue light directly into your eyes. If all else fails, use your phone in the brightest setting. 
    5. Avoid consistent exposure to cool artificial light (>5000K). Such exposure is fine for a few hours during your peak period, but avoid continuous exposure to protect your eyes and hormonal balance. You can mitigate such exposure by wearing daytime blue-light-blocking glasses (VivaRaysBlockBlueLight). These blue blockers have yellow lenses, remove about 50% of the blue light spectrum, and turn cool light into warmer light.
    6. You want to start blocking all blue wavelengths during the slowing down period. You can achieve this by using nighttime blue-light-blocking glasses (VivaRaysBlockBlueLight). These have orange/red lenses and block 100% of blue and some green light. This way, you ensure that cortisol is rained and melatonin production is uninhibited. Failing to do so will phase advance your circadian rhythm, impair sleep, and mess up the hormonal tides in your body.
    7. If you are using a computer for work, investigate the option of using software that allows you to manage the color temperature and brightness automatically. IRIS or f.lux are the best options.
    8. Consider adding a red/infrared light source (SaunaSpaceBlockBlueLight) to your working environment. Why? Because if you spend most of your time indoors, you are deprived of red and especially infrared light. These frequencies make up more than 50% of sunlight, and their main job is to regulate the repair and regeneration of your cells.
    9. Treat yourself before or after work. A sauna session is one of the best options to support your body and fill up your tank of red and infrared light. Imagine sitting in your infrared sauna a few times a week. Another good option is a warm bath.
    10. Use circadian-friendly lighting at your workplace. Full-spectrum bulbs/downlights are available where the spectral composition can be switched. Balanced lighting options are also available for public facilities. But bear in mind that the lighting requirements for patients (e.g., in a nursing home) differ from those who work the late/night shift.
    11. Light is just one part of a successful mitigation strategy for shift work. Make sure to read Circadian rhythms and shift work – the ultimate guide.

Hopefully, this will help you implement better light choices in your home and workplace. Mind your rhythm, mind your light.

People can lead a better life by changing their light and energetic environment they are in.

– Dr Leland Stillman

For more information on light and circadian rhythms, dive into the learn section of the Circadian App and watch the following the videos: 

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