Light hygiene

EVERYTHING YOU WANTED TO KNOW ABOUT LIGHT AND SLEEP IN ONE PLACE

Light is one of the decisive factors that influence our sleep, our energy levels, and our health.

Find out how you your brain and body react to light, and optimize your health based on the tips below.

Follow the sun

For a healthy circadian rhythm and sleep, it is important to expose yourself to natural daylight, or at least to artificial lighting that mimics its properties. As a species, we have evolved to utilize solar radiation in many ways, of which the most important is to divide the day into the illuminated, active period, and the dark, resting period. Daylight used to be the main signal telling us when to switch from day to night. When electric light bulbs and later electronic displays took over the world, allowing us to spend most of our time indoors, the light signal got confused, resulting in all sorts of health complications.

01

What is the first key property of daylight?

The first key parameter of solar radiation is high intensity.
During the day, spend outdoors as much as possible. When indoors, make sure the room is brightly lit either with daylight or artificial lighting resembling daylight. High light levels make you feel alert, they help you concentrate, improve your brain and body performance, even your mood is better. Whatever you decide to do, you can give it your best in a brightly lit environment. Just remember not to look directly in the sun or any other lightsource directly. To protect your eyes, avoid bare lightbulbs or any other clearly visible lightsources at all times. Inevitably, after 13 to 18 hours you start to feel tired.
To relax, allow yourself some evening light, either the real thing ie. the sunset, or a dim and very warm artificial light.
For a good night of sleep, darkness is the best. If you do need to get up during the night, imitate firelight, the light source of our ancestors. The rule is simple, the later is gets in the day, the dimmer the light.
A big difference between bright light during the day, dim light in the evening, and darkness at night, will improve your efficiency at anything and everything you decide to do.

02

What is the second key property of daylight?

Daylight has a very variable blue light component. Around noon, all the wavelengths of visible light, from violet and blue through green and yellow to orange and red, are present in roughly equal proportions, and therefore the resulting colour we perceive is pure white. Around sunrise and sunset, however, the violet, blue and green components get absorbed more in the athmosphere, making daylight much warmer in colour. This gradual decline of blue and green components is a signal that night is approaching.
When there is no blue light left, our brain tells the whole body to start preparing for sleep, sending melatonin into the bloodstream. In the morning, our eyes detect light through closed eyelids. Soon after sunrise, when blue and green photons starts to appear, it is a signal to us to get up. Melatonin is no longer needed in the blood (our mitochondria produce lots of it when triggered by daylight's near-infrared radiation, but this melatonin stays inside cells, never entering the bloodstream).
At night on the other hand, two natural lightsources are available: moonlight, which is very dim (too dim to read, too dim to see colours), and firelight, which contains only the yellow, orange and red components of the spectrum (and comes from the ground, and is also rather dim). Any lighting that resembles fire is safe at night. Unfortunately, modern devices such as computer and mobile phone screens, TV sets and most LED lightsources emit lots of blue and green light. Our brain interprets the high blue component as a signal of the day, regardless of what the clock says and how many hours you have been awake. Even street light shining into your bedroom can make your brain think the sun hasn't set yet. Sleeping during the day is dangerous, so your brain tries to keep you awake as long as possible, making you very tired. You may even lose your natural rhythm of sleep and wake, activity and rest altogether, getting locked in a permanent late evening, exhausted but unable to stay asleep.
To stay healthy, happy and full of energy, you need daylight during the day, or at least full-spectrum artificial white light as similar to daylight as possible, with high portions of both blue and red spectral component. In the evening, light around you should be much warmer, low in blue and green components. Some 90 minutes before bedtime (or 9.5 hours before your planned getting-up time) and at night, no blue or green light should enter your bedroom, and total darkness is the best.

03

What is the third parameter of imitating the sun?

The third parameter by which we mimic the sun is the position of the light source. It's simple: during the day the sun is above our head, in the evening it is approximately at eye level - and at night it shone only with fire on the ground, ie below eye level. We should shine the same way: during the day above eye level, in the early evening and at sunset time at eye level, and later in the evening and at night below eye level. The orange light shining from below is so naturally soothing not only in its color and in that it does not prevent the formation of melatonin, but also in its position (orange light from above does not exist in nature, because during the day the sun shines full spectrum above our heads).

Light during the day

The correct artificial light during the day is diffused and shines from a large area. This is best achieved by reflecting light against a ceiling or wall, but the light source must be powerful to have sufficient intensity after reflection. (Note for experts: the current standard of 300 - 500 lx is completely insufficient in terms of sleep quality for rooms with long-term stay during the day. The minimum is 800 lx at UGR 0-19.) On the contrary, light in the evening and night is localized, not very intense, does not dazzle and shines below eye level - use an opaque shade.

For work and study, lighten the table with a local lamp with a shade (to prevent glare) and use a bright white source with a balanced proportion of all colored components.

Darkness is a symbol of a healthy bedroom

Sleep in the darkest possible darkness . The better darkening you achieve, the better your body regenerates in sleep. Sufficient darkness is such that you do not see your own hand in front of your eyes. If you wake up in the middle of the night and see so well that you can get up and walk to the toilet without turning on, you have too much light in the bedroom.

Use blackout curtains, black cloth glasses, or both. If you need to have time information during the night, use a clock that glows red or monochrome orange (pure orange light that does not come from mixing red and green), or cover the screen with a foil that does not let other colors of light through.

We don't need lights at night

Cover the red (or orange) foil of the smaller LCD display and lights, which emit a blue and green component at night, thus disrupting our circadian rhythm and delaying to stop the production of the hormone melatonin. - This negatively affects our sleep and long-term health. ⁠

Seal smaller sources of white, blue and green light, such as LCD displays for home appliances, babysitters and cameras (baby monitors), control panel displays for heating, alarms and digital alarm clocks, or smaller illuminated and flashing lights on the TV, translucent red foil. PC monitors and Wi-Fi router. You'll definitely find other resources you'll want to paste, such as the glowing Apple logo on older MacBook laptops. Red foil is more effective in blocking because it also blocks green wavelengths, but it can result in the display not being legible. If you need to keep the display legible, we recommend trying red and orange foil. Their effect is different for each display - it is not possible to predict whether the readability of the red foil display will be maintained. ⁠

Best at night without displays

Before going to bed and at night, avoid the electronic displays of mobile phones, tablets, computers and televisions, or use a red filter.
Applications like F.lux often only dim the blue and green components of the displays, but do not completely remove it. 90 minutes before bedtime (more precisely 9.5 hours before getting up in the morning) and during the night, we recommend wearing red glasses if you need to work with display devices.
For Apple devices, it is ideal to set a red filter, which eliminates the need to wear red glasses with iPhone, MacBook and iMac displays. A video guide to setting up the red display is on our YouTube channel.
Iris software is available for all operating systems, which can fully eliminate the blue and green components of displays. Iris is available for mobile phones, tablets and computers - it supports Windows, Mac, Android and Linux operating systems. In addition to this function, it is also suitable for working and reducing the brightness of monitors.

Light hygiene according to your age.

Children

0 - 12

It takes a few months for newborns to develop their circadian system and they begin to be awake significantly more often during the day and sleep for longer periods of time at night. As soon as the child's temporal system is established, it reacts very sensitively (more sensitively than in adults) to the intensity and color (spectral composition) of light. In childhood, therefore, the effects of deliberate manipulation of light are most apparent! Exposure to bright light with a high proportion of the blue component stimulates children to high alertness and activity, in light of lower intensity and with a smaller proportion of the blue and green components of the spectrum, they quickly lose concentration, attention and either start to wander or become restless as a result mood drop (a manifestation of a momentary drop in serotonin production).

Teenage

13 - 25

Perhaps everyone has noticed that teenagers prefer to go to bed after midnight and wake up around ten. The reason is not laziness, but a real, scientifically proven shift of the chronotype towards extreme evening values , which occurs around the age of 15. Sometime around the 25th birthday, the chronotype begins to return to normal. Up to the age of 18, the need for sleep is greater than that of adults , which is why teenage children are the most affected by sleep debt. Their bodies cannot fall asleep at 9 o'clock in the evening, but they do not get the necessary 9-10 hours of sleep because school classes start at 8 o'clock.

Adults

26 - 60

Some people throughout their lives function better in the morning and in the morning, while others feel best in the afternoon and evening. It's called a chronotype, and there's not much you can do about it. However, extremely early birds and nesting owls are actually very rare in the adult population. Far more often, the onset of sleepiness shifts to the late hours of the night due to improper lighting hygiene . Especially in the last 20 years, the range of various artificial light sources is so wide, electronic displays are so widespread and the human need to live in inappropriately lit interiors is so great that maintaining good lighting hygiene requires knowledge of specialist information, a lot of effort, enough money and considerable mental discipline. The only good thing is that proper lighting hygiene is also pleasant to the senses, and everyone who has the opportunity to compare lighting suitable and unsuitable for a given time of day intuitively chooses the right light.

Seniors

61 - 100

The properties of the human eye begin to deteriorate gradually from the age of 40. After the age of 60, these changes are already noticeable, and from the 80th birthday they cause great difficulties that are difficult to compensate for. For one thing, the lens becomes cloudy, so less light enters the eye. The permeability of the vitreous further deteriorates, so more light is scattered inside the eye, causing glare and not hitting the retina. The state of the retina also worsens and the pupil shrinks. All this means is that the brain needs more light to even register that it's daytime. If this fact is combined with reduced mobility, which forces older people to spend more time indoors, and with poor-quality lighting in many interiors (low light intensity, small proportion of the blue component, glare), it is no wonder that older people suffer from sleep disorders to an increased extent malfunctions . In many cases, due to long-term lack of sleep, beta-amyloid waste accumulates in the brain, covering neuronal connections in areas responsible for long-term and short-term memory, and Alzheimer's disease develops. However, scientific studies have shown that people suffering from Alzheimer's (or senile dementia) respond well to improvements in lighting conditions - more light during the day, less light in the evening, more darkness at night . The progress of the disease slowed down or even stopped in the experimental subjects, and the nursing staff noted a reduction in the symptoms of Alzheimer's disease and an improvement in the mental state of the patients.
So if you are over sixty, go out in the daylight as often as possible and remember to turn off the TV 1.5 hours before going to bed in the evening .

"I firmly believe that these tips will help you optimize the quality of sleep, which is so important for all of us.
Thank you."