Sleep in Space
Zero gravity orbit is not always restful.
Posted Jun 15, 2017
Humans adapt. We live in trackless deserts, on the tops of mountains, in pestilential jungles, in prisons and hospitals. To survive we sleep, for we need sleep like food. We adapt to sleeping in space.
At the recent sleep meetings I had the chance to talk with Dr. Erin Flynn-Evans, who runs the Fatigue Countermeasures Laboratory at NASA Ames Research Center in California. So what is it like to sleep in space? And how well do astronauts sleep?
As it turns out, not all that well.
The Space Station Environment
The space station is not like earth. Gravity is zero. Orbiting the earth denies the normal sense of night and day. Every 92 minutes you see a new sunrise. Work is required every day, often for much of the day. It's crowded. Everything you ingest is recycled. There are no parks, no vacations. You see the same people every day.
And people sleep six hours a night. According to Dr. Flynn-Evans, they have averaged six hours a "night" since the beginning of human space flight over 50 years ago.
The National Sleep Foundation spent years deliberating before recommending most people most people need 7-8 hours sleep a night for better health. If people need sleep like food, why are astronauts, often in terrific physical shape before they go into space, sleeping an amount of time that potentially interferes with their performance, function, and long term health? There are lots of reasons:
1. Normal circadian (24 hours) cycles don’t apply. You’re in orbit. You don’t experience normal day and night. Orbital cycles of 92 minutes cycles interfere with normal body clock physiology. Many of the astronauts end up with circadian misalignment—their bodies are not synched with the 24 hour cycles of their lives and work.
2. Weightlessness—we did not evolve with zero gravity. Pretty much everything changes physiologically when living where there's no gravity.
3. Confined, noisy conditions. You can’t easily walk out of the space station. If you do, you will experience major changes in sunlight and darkness over very short periods. Your diet is different. Machines, often loud, are everywhere.
So what do people do to adjust? Frequently, they take sleeping pills. Just as folks do dealing with jet lag on earth, astronauts readjust their clocks with sleeping pills. Apparently the Russians use a variety of sleep aids.
Where people sleep also changes. There’s no need for a standard bed. You can sleep on the ceiling, on the floor, upside down or sideways. Or you can float. Many astronauts become “floaters,” untethered from walls. Some prefer a tether, and sleep vertically.
But the lack of sleep is eventually felt. There are many reasons astronauts take a long time readjusting to life on earth. It's just reintroduced gravity. There’s the change in their bones, their guts, their gut bugs, their muscles. Yet there is also the effects of sleeping less for long periods of time. Even when people are in terrific shape, this takes its toll.
Going to Mars
NASA may not get humans to Mars first. Some might arrive under the auspices of Elon Musk.
It will not be a simple journey. There will be years of zero gravity. There will be recycling of air and water and urine and stool for long periods. Highly confined conditions.
Making a sleeping environment in a tiny capsule that is quiet and calm and dark will not be easy.
Fortunately, the circadian disruption of orbital flight will be less of an issue. Light and dark will not be shifting every 90 minutes. More normal clocks may be possible.
Until you get to Mars. Martian days are 39 minutes longer than Earth days.
Not much time, you might think. But even a few minutes difference each day eventually leads to highly disrupted biological clocks. Ask people who are blind and don’t have functional retinal ganglion cells that tell their brain when the 24 hour day starts. If they go to bed at 11 PM tonight, they’ll want to fall asleep the next night at 11:10 or 11:15, then the next night ten or fifteen minutes later.
Until they’re sleeping during the day and the night. And their basic physiology is so disrupted that they can’t function in any normal way.
Will humans on Mars continue their 24 hour pattern, the one inbuilt in every one of our 10 trillion human cells and 40 trillion bacterial ones? If we do, we will be out of synch with the Martian environment. And basic physiology may remain perpetually disrupted.
Dr. Flynn-Evans and others are trying to figure out what to do. Humans will adjust. Our biological intelligence lets us adjust to almost everything.
But there is always a price.
For those who saw the movie “The Martian,” and think that Mars and the Moon will support a human population if our own planet proves uninhabitable, think again. Four billion years of life and evolution will need to be overriden to live comfortably in space.
We better keep the planet we have for a long, long time.