Astronauts assigned to long deep-space missions should adhere to healthy sleep/activity patterns established on Earth if they are to deal with the risks of prolonged confinement, including lethargy and other symptoms that jeopardize performance levels and overall physical health, according to findings from a first-of-its-kind study by U.S. researchers involved in the joint Russian/European Space Agency Mars500 simulation.

The mock mission, which concluded Nov. 4, 2011, involved a half-dozen volunteers confined for 520 days in Moscow and closely monitored during the simulated roundtrip to Mars, which included eight days of simulated surface activities. The volunteers, all males ages 29 to 40, came from France, Italy and China and Russia.

The Mars500 crew experienced alterations of life-sustaining sleep patterns and neurobehavioral consequences that must be addressed for successful adaptation to prolonged space missions, according to investigations carried out by researchers from the Perelman School of Medicine at the University of Pennsylvania and the Baylor College of Medicine in Houston.

The volunteers became increasingly sedentary, sleeping and resting more as the lengthy simulation unfolded. A majority of the men also experienced one or more disruptions to their sleep quality — deficits in alertness and changes to the sleep/wake interval and timing. The symptoms suggested a harmful break in the synchronization of circadian rhythms.

“A takeaway message from this line of research is the life-sustaining importance that healthy sleep duration and timing plays for everyone,” said psychologist David Dinges, professor and chief of the Division of Sleep and Chronobiology in the Department of Psychiatry at Perelman, as well as co-lead author of the study, which was published in Proceedings of the National Academy of Sciences in Jan. 7 online editions.

Researchers monitored the crew’s rest-activity patterns as well as performance and psychological responses to determine the extent to which sleep loss, fatigue, stress, mood changes and conflicts occurred during the mission. Body movements were continuously recorded using actigraphs, or wrist monitors. Light/dark changes were recorded, and the crew participated in weekly computer-based neurobehavioral assessments to help identify changes in activity levels, sleep quantity and quality, sleep/wake intervals, alertness and workload.

The Mars500 simulation was developed by the Institute of Biomedical Problems, an arm of the Russian Academy of Sciences. U.S. participation was facilitated by the NASA-funded National Space Biomedical Research Institute.