Sleep on manned space flights: Zero gravity reduces sleep duration Alain Gonfalone  Pathophysiology  Volume 23, Issue 4, Pages 259-263 (December 2016) DOI: 10.1016/j.pathophys.2016.08.003 Copyright © 2016 Elsevier B.V. Terms and Conditions

Fig. 1 Sleep of 4 astronauts. Average sleep structure for four astronauts. Results from nights on ground (baseline) and in space (mission) were averaged for each of the four astronauts separately. The height (y axis) of an open non-REM area corresponds to the average power of slow waves in that particular non-REM period. The height of hatched REM areas has been arbitrarily chosen for display. Data are arranged by age of astronauts, with age increasing from right to left and top to bottom [34]. The red arrow indicates that the REM sleep latency is shorter during the space sleep and the blue arrow that the total sleep duration is also shorter. As a side effect, the efforts to maintain the body in postures that oppose the inherent weight are reduced as well as the fatigue after the wake period. This may have an influence on the duration of the slow wave sleep, which is supposed to contribute to the body rest, but needs still to be verified. An incontestable observation confirms this proposition: ‘In space, the latency to the first REM episode was shorter’ [34]. Pathophysiology 2016 23, 259-263DOI: (10.1016/j.pathophys.2016.08.003) Copyright © 2016 Elsevier B.V. Terms and Conditions