Space travel enthusiasts promise adventure, out-of-this-world views and bouncy antigravity rooms, but scientists have now found another selling point for interstellar R&R: Humans sleep in space more soundly than on Earth.
During a study of two 1998 space flights, five astronauts stopped snoring almost completely. The astronauts also experienced a significant decrease in sleep-disturbing periods of breathing cessation, called sleep apnea, as well as periods of slow and shallow breathing called hypopnea.
Scientists from the University of California, San Diego, Brigham and Women's Hospital, and NASA Ames Research Center published the research in this month's issue of the American Journal of Respiratory and Critical Care Medicine.
The gravity of the matter
Though sleeping in space is probably in the far-off future for most Earthlings, understanding gravity's role in respiratory sleep disorders does benefit many: 40 million Americans snore habitually and 18 million suffer from sleep apnea. Obesity, sleeping positions and the size of airways in the soft palette are already known to play a role in sleep disturbances.
"This is the first direct demonstration that gravity plays a dominant role in the generation of apneas, hypopneas and snoring in healthy subjects," the team wrote.
Gravity squeezes the upper respiratory system when the muscles relax during sleep, said Associate Director of the Sleep Disorder's Program at Brigham and Women's Hospital, Steven Shea. He worked on the newly published research.
This restricts the airways and causes that all-too-common locomotive snoring sound, as well as the choke-inducing apnea. Without gravity's tug, he said, the airways are more buoyant, allowing for easier breathing.
Losing sleep in space
Nonetheless, astronauts face other challenges to a good night's rest. The study found that even though respiratory disruptions were at a minimum, the astronauts slept fewer hours in space than on Earth. Previous research has found astronauts sleep an average of only six hours while in orbit, and sleep hypnotics are 45 percent of the medications taken on board.
Shea said that like on Earth, excitement and stress can cause shortened sleep times.
"If the world is looking at you, and you have to perform many new tasks in a new environment, it might make you lose sleep," Shea said.
On the other hand, there are space-specific problems such as pervasive motion sickness, and the setting and rising of the sun every 90 minutes that only astronauts have to overcome, for now.
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