The living space project team investigated how we can improve the relationship between health and spaces. At the Think Human Exhibition, under the theme of “creating health through spaces,” the project team considered how to create spaces that correct our internal clocks. As one aspect of life in modern society, we live in cities that are too bright at night and lead us to nocturnal lifestyles far removed from natural rhythms. So from what perspectives should we approach space creation?
The inseparable triad of sleep, light, and internal clocks
We want to sleep peacefully at night and wake up refreshed in the morning, but this is not so easy these days. Our world today is a convenient one, but there are increased instances of sleeping disorders like “social jetlag” and chronic sleep deprivation, confusing our internal clocks. If we continue on this path, our society fifty or one hundred years in the future may be characterized by irregular circadian rhythms. In this exhibition, the project team demonstrated future living spaces that aim at healthy lifestyles that follow our circadian rhythm. The team also hosted a talk by Professor Masashi Yanagisawa, a specialist in sleep medicine and director of International Institute for Integrative Sleep Medicine at University of Tsukuba, who spoke about the relationship between sleep, our internal clock, and light.
He described how we do not even know the fundamental reasons why humans sleep, or the mechanisms behind drowsiness. “Sleep is considered one of the biggest black boxes in modern neuroscience. We do know that sleep is vital to life. Rats will die from sleep deprivation after ten days to fourteen days, for example. What we don’t know, however, is why it is vital. You might have read somewhere that sleep is our brain’s chance to get some rest, but our brains are actually very active during sleep, so it would be wrong to think of them as merely resting, or doing nothing. To use the analogy of a computer, it’s more like the power is still on but the brain has gone offline for maintenance. We also know that not only vertebrates, but also even insects and nematodes—actually, any animal with a brain, or an equivalently complex nervous system—must sleep. At first glance, sleep seems to be counterproductive, even an existential risk. So the fact that all animals sleep anyway must mean that the benefits gained from sleeping outweigh such risks. Even so, we don’t know specifically what those benefits are. The neuroscientific basis for drowsiness is another mystery. So the field of sleep science is still at a stage where we cannot answer even the most basic questions.”
From previous research, we know that drowsiness is primarily controlled via two processes. The need for sleep accumulates when we remain awake for a long time, and then dissipates as we sleep. This is the result of a homeostatic mechanism for determining the amount of sleep we should get each day. If this were the only system in place, however, we would feel most awake when we got up in the morning and become increasingly drowsy as the day went on. Our internal clock, therefore, serves as a mechanism to suppress daytime drowsiness so that we might retain a more-or-less constant level of wakefulness throughout the day.
The living spaces project team started preparing for the exhibition by discussing the methods by which our internal clocks are controlled. As Yanagisawa described, “There is something like a ‘master clock’ deep within our brain, in a location called the suprachiasmatic nucleus, that controls our overall internal clock. Each of our cells has a clock of its own, but it is this master clock that controls the clock for the entire body. As to what in turn controls the master clock, light from the outside world plays a large role.”
Our retinas have sensors that act something like a light meter, and are designed to react to bright blue light at wavelengths of 400–500 nanometers. The master clock is synchronized with the earth’s rotation through the transmission of light information from these retinal light-meter sensors via nerve fibers to the suprachiasmatic nucleus. When our retinal sensors detect strong short-wavelength blue light in the early morning, our master clock advances a little (around one hour per day), and when exposed to the same kind of light in the evening, the master clock falls a little behind. Our body uses this system as a way to gradually overcome jetlag.
Illumination that imitates natural light adjusts our internal clock
Our internal clock has a close relation with light, from which the circadian rhythm is formed. How we illuminate our living spaces thus has profound effects.
“From the perspective of effectively adjusting our internal clocks,” Yanagisawa said, “I recommend living spaces with low-level, yellowish, low color-temperature lighting and the use of indirect lighting. When we spend our evenings under intense white light with a high color temperature, shining brightly from the ceiling, we experience the phenomenon I talked about before of a master clock running late. There has been a lot of recent discussion of problems arising from the blue light emitted by smartphones and other devices, but considering the size of those screens, they don’t really produce all that much light. More problematic is that our rooms are too bright. Bright rooms at night are an environment in which social jetlag can easily arise.”
In this exhibition, the project team presented a space named Reset Blue that emits two colors of light from entire wall surfaces: strong blue light in the morning, and soft yellow light as bedtime approaches. Such variation in lighting over time will maintain our circadian rhythm.
“Humanity has lived under natural lighting conditions for millions of years, and evolved accordingly,” Yanagisawa said. “Our internal clocks and retinal sensors are optimized for that lighting environment. The lighting environment we have created over the past century, though, can only be described as a biological abnormality. I think it’s safe to say that it is healthiest to live in a natural rhythm, one in which nights are dark and mornings are bright.”
Through this project, this team learned that circadian rhythms are closely related to fundamental parts of humanity. Our internal clocks maintain a rhythm that calls for sleeping in dark nighttime environments and waking up with morning sunlight, like the one we evolved with in nature, and this rhythm contributes to our physical and mental health. The living space team concluded that this will not change over the next fifty or even one hundred years.
Reset Blue attempted to improve our surrounding environment to correct irregularities in our internal clocks. This is one example of how Teijin will continue to work toward creating better spaces so that as many people as possible can live a healthy lifestyle, one aspect of the improved quality-of-life that Teijin aims for.
Nature and Science of Sleep