Astronauts on a mission to Mars may encounter meteorites, exposure to radiation and microgravity, but it also seems they will suffer from poor performance due to a disrupted sleep-wake cycle. With manned interplanetary travel predicted to start this century, this suggests that it's our understanding of space medicine, and not just the rocket technology that we need to develop before we can visit other planet.
The Mars 500 mission simulated the conditions of an actual mission to Mars. Six volunteers were isolated for 520 days in a small spacecraft-like facility inside a Russian warehouse. The aim was to measure the physiological and psychological impact of a real mission.
Now, a paper published in the journal PNAS shows that the volunteers experienced decreased activity levels and disrupted sleep-wake cycles, resulting in poorer performance and a reduction in vigilance.
Mathias Basner from the Perelman School of Medicine at the University of Pennsylvania and colleagues collected recordings of each volunteer's activity and light exposure, through a sensor worn on the wrist. The volunteers also undertook weekly computer-based behavioural assessments.
The researchers found that activity level, measured as time spent in active wakefulness in any 24 hour period, sharply decreased throughout the first 13 months of the simulation. The amount of time the volunteers spent resting increased by over 50% throughout the mission, while sleep time only increased by an average of 8%.
Each volunteer showed a different pattern of changes, but the majority experienced disrupted sleep-wake cycle, a drop in performance, reduction in sleep quality or a combination of the above.
The authors argue that this demonstrates a need for circadian control through light exposure and meal times, and that:
"A balance must be struck during human exploration of space between the critical need for adequate time for sleep and rest and the need to maintain activity levels for physical and physiological fitness."
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