Characteristics of the sleep of men in simulated space flights.

A study of the sleep of men in simulated space flight has shown that, during different effects (diminished motor activity, noise, rotation), monotony and time of the exposure is the general pathogenetic factor producing sleep disturbances. The monotony factor was responsible for typical changes in sleep function (difficulty involved in falling asleep, disturbed continuity of sleep as a process, decline in the depth, etc.), whose degree was related not only to the professional importance of the experiment but also to the individual intolerance to the main exposure. In these cases, the action of somnogenic mechanisms developed against the background of the action of analyzers (vestibular, accoustic, proprioceptive) that were under load and whose excitation during hypokinesia, noise, and rotation, especially in poorly adapted people, led to cumulation and was expressed in the phenomenon of spontaneous awakening. In addition to that, the genesis of dyssomnia, particularly during bedrest and water immersion, included hemodynamic disturbances induced by blood redistribution due to the recumbent position and monotonous motor activity. The psychosomatic feelings (congestion, edema, irresistible desire to stand up and stretch) brought about emotional strain which was later enhanced by the duration of the exposure.