Only four people have spent more than a year in space, the record being 437 days set by Valery Polyakov on the Mir space station, but this century humans are expected to take the long trip to Mars.
Prolonged isolation, decreased levels of activity, and changes to the sleep patterns of astronauts are big concerns for any deep-space expedition. These factors may affect astronauts' psychology and ability to perform mission tasks.
In a study published by the Proceeding of the National Academy of Sciences today, Jan. 7, researchers looked at how alterations to sleep and activity levels affect the performance and mood of six volunteers in a 520-day simulated mission to Mars.
"The success of human interplanetary spaceflight, which is anticipated to be in this century, will depend on the ability of astronauts to remain confined and isolated from Earth much longer than previous missions or simulations," said David F. Dinges, a professor at the Perelman School of Medicine and co-lead author of the new study, in a press release "This is the first investigation to pinpoint the crucial role that sleep-wake cycles will play in extended space missions."
The simulation, developed and operated by the Institute for Bio-Medical Problems of the Russian Academy of Sciences, started June 3, 2010, when the volunteers were locked into a 550-cubic-meter spacecraft-like confinement facility in Russia. The crew performed 90 experiments while participating in realistic scenarios, like having limited resources and delayed communications with mission control.
The crew's activity levels, sleep-wake dynamics, and light exposure was determined using monitoring devices on their wrists. A weekly computer-based neurobehavioral exam was also used to identify changes in the crew’s activity levels, workload and sleep quantity and quality.
As the mission continued, the crew became less active and increased their sleep and rest times. Most of the crew also experienced disturbances to their quality of sleep, alertness deficits, or changes to their sleep-wake cycles. As a whole the crew obtained 673 more hours of sleep in the second half of the mission compared to the first half.
Interestingly during the last 20 days, the time spent awake and intensity of the crew drastically increased, while sleep and rest time decreased. Mission managers indicated this was due to the anticipation of the mission coming to an end.
"A takeaway message from this line of research is the life-sustaining importance that healthy sleep duration and timing plays for everyone," Dinges said. "As a global society, we need to reevaluate how we view sleep as it relates to our overall health and ability to lead productive lives. Whether it is an astronaut being challenged to reach another planet or a newborn baby just learning to walk, the human body's need for sleep is as essential as our need for food and water and integral to our ability to thrive."
