Astronauts Will Have Special Sleep Needs On Prolonged Space Missions
January 8, 2013

Simulated Mars Mission Reveals Critical Sleep Data For Astronauts

April Flowers for - Your Universe Online

In an attempt to simulate a 520-day space mission to Mars, researchers in a groundbreaking new study lead by the Perelman School of Medicine at the University of Pennsylvania and the Baylor College of Medicine, have analyzed data on the impact of prolonged operational confinement on sleep, performance, and mood in astronauts. This new study, published online in the Proceedings of the National Academy of Sciences, demonstrates alterations of life-sustaining sleep patterns and neurobehavioral consequences for crewmembers that need to be addressed for humans to successfully adapt to prolonged space missions.

"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, PhD, professor and chief, Division of Sleep and Chronobiology in the Department of Psychiatry at the Perelman School of Medicine. "This is the first investigation to pinpoint the crucial role that sleep-wake cycles will play in extended space missions."

Developed by the Institute for Biomedical Problems (IBMP) of the Russian Academy of Sciences, the 520-day simulation was sponsored in part by the European Space Agency (ESA). The mission began on June 3, 2010 when the hatches were closed on a 550-cubic-meter IBMP spacecraft-like confinement facility in Russia. An international, six-man team of volunteers was involved in more than 90 experiments and realistic scenarios designed to gather psychological and medical data on the effects of a long-term deep space flight. The simulated mission was broken into three phases: 250 days for the trip to Mars, 30 days on the surface, and 240 days for the return to Earth for a total of 520 days.

The U.S. team monitored the crew's rest-activity patterns, and performance and psychological responses to ascertain the extent to which sleep loss, fatigue, stress, mood changes and conflicts happened during the 17-month confinement.

The team conducted measurements, including continuous recordings of body movements using wrist actigraphy — a noninvasive means of estimating sleep and movement intensity. Other tests included light exposure and weekly computer-based neurobehavioral assessments to identify changes in the crew's activity levels, sleep quantity and quality, sleep—wake intervals, alertness performance, and workload throughout the simulation.

Actigraph device data revealed that sedentariness among the crew increased across the mission. Decreased waking movement and increased sleep and rest times illustrated this increase of sedentary behavior. One or more disturbances of sleep quality, alertness deficits, or altered sleep—wake intervals and timing were experience by the majority of crewmembers, suggesting inadequate circadian synchronization.

"Taken together, these measurements point to the need to identify markers of differential vulnerability to abnormal decrease in muscular movement and sleep—wake changes in crew members during the prolonged isolation of exploration spaceflight and the need to ensure maintenance of the Earth's natural circadian rhythm, sleep quantity and quality, and optimal activity levels during exploration missions," said Mathias Basner, MD, PhD, MSc, assistant professor of Sleep and Chronobiology in Psychiatry at Penn.

Successful adaptation to such missions, the team finds, will require astronauts to transit in spacecraft and live in surface habitats that will mimic aspects of Earth's sleep-wake activity cycles artificially, such as appropriately timed light exposure, food intake, and exercise.

The team suggests that their findings could also have implications for the increasing prevalence of sleep and circadian rhythm disorders in mainstream society. People in industrialized societies, the authors note, are living more sedentary lifestyles, existing with prolonged artificial light exposure and disruptions in healthy sleep patterns due to education and work schedules, leading to other co-morbid health conditions such as obesity.

"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."