Earth to Mars: Are You Awake Out There?

Mars simulation reveals sleeping problems and circadian rhythm disruptions

(RxWiki News) A trip to Mars involves all kinds of challenges for the human body. It would take over a year just to get there and back. How will astronauts' bodies cope in terms of sleep cycles?

A group of researchers decided to find out with the help of six men who volunteered for a lengthy isolation period designed to simulate a trip to Mars.

Over 90 experiments during about a year and a half in isolation revealed problems in the men's sleeping schedules, sleep quality and alertness.

These findings mean a trip to Mars could cause significant problems for a crew's sleeping schedules and alertness.

The study also offers more evidence of possible problems that regular Earthlings may continue to experience with sleeping patterns and our body clocks, due to artificial light and societal restrictions on our schedules.

"Maintain a regular sleeping schedule."

The study, led by Mathias Basner, MD, PhD, from the Division of Sleep and Chronobiology at the University of Pennsylvania's Perelman School of Medicine, aimed to get a sense of how six astronauts' sleep and wake patterns might be disrupted during a mission to Mars.

One estimate for the time it would take to get to Mars is about 250 days, or just over 8 months. The trip back would be about the same.

Therefore, six men volunteered to spent 520 days in a simulation experiment in Russia that began on June 3, 2010. That includes the 250 days to and from Mars, plus 30 days on the surface of the red planet.

The men wore actigraphs on their wrists which recorded their activity levels to estimate their sleep and wake times. Their exposure to light was also recorded during the simulation, and they underwent more than 90 experiments to provide data about their physical and mental states during the mission.

The crew members also underwent a computer-based assessment of their cognitive behavior each week. These assessments measured the crew's activity levels, sleep quantity, sleep quality, how frequently they went to sleep and then were awake, how vigilant they were and their workload during the experience.

The crew's overall fatigue, stress, mood changes and conflicts were also recorded and analyzed.

During their 17 months of confinement, the crew grew more and more sedentary. They showed increased sleep and rest times and decreased wakefulness. Their light exposure also decreased during the mission.

Four of the participants reported at least some problems with their sleep quality, changes in their sleeping/waking frequency and alertness.

One had disruptions to his pattern of waking and sleeping, and two flipped when they were sleeping from nighttime to daytime. One experienced sleep deprivation that led to a slower and/or poorer performance in his neurology and/or work duties, and two reported frequent problems with their sleep quality.

The authors wrote that these difficulties suggested problems with their circadian rhythms, which are the internal "body clocks" that regulate various body processes, including sleep.

"The results point to the need to identify markers of differential vulnerability to hypokinesis [abnormally slow movement] and sleep-wake changes during the prolonged isolation of exploration spaceflight and the need to ensure maintenance of circadian entrainment, sleep quantity and quality, and optimal activity levels during exploration missions," the authors wrote.

This means that the researchers need to identify the causes of the crew's slowing down during the mission and the causes of their problems with sleeping and waking patterns.

It also means they will need to find a way to help crew members maintain their regular circadian rhythms on such a long mission, as well as maintain their sleep quantity and quality.

"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 co-lead author David F. Dinges, PhD, from the Division of Sleep and Chronobiology at the Perelman, in a release about the study.

Yet the study also points to potential future problems for regular people on Earth, where problems with sleep patterns and circadian rhythms have been increasing "with limited exposure to natural geophysical signals, widespread sedentary activities, and primarily artificial light exposure," the authors wrote.

Past research has shown that sleep restriction can arise from the disruption of natural circadian rhythms due to alarm clocks, work schedules, TV programming times, school start times and daylight saving time changes.

"The essential need for humans to maintain sleep-wake activity cycles synchronized to the circadian biology that temporally coordinates human health and behavior appears to be as important on Earth as it will be en route to Mars," the authors wrote.

The study was published January 7 in the Proceedings of the National Academy of Science. The research was supported by NASA's National Space Biomedical Research Institute, by the Institute for Experimental Psychiatry Research Foundation and by the European Space Agency. No conflicts of interest were noted.

Review Date: 
January 7, 2013