[Effect of prolonged unidirectional migration of the sleep--wakefulness rhythm phase on human physiological functions, mental productivity and sleep].

The paper gives the results of three 30-day experiments carried out to study the effect of migration of the sleep--alertness cycle on physiological functions, psychic productivity and sleep of man. The migration was agravated by the initial change of the cycle which varied from +/- 7 to +/- 11 hours. All test subjects showed a counter-clockwise migration which amounted to a 1.5 hour shift every 4-5 days. All test subjects demonstrated functional cerebral changes, decline of psychic productivity and sleep disorders. The level of those disturbances depended on the value of the initial shift of the sleep--alertness cycle and on the cumulation of the migration effect. Those disorders were noted even when the prechanged sleep--alertness cycle approximated the normal pattern as a result of migration. The results indicate that the migrating day--night pattern, particularly in combination with the initial shift of the sleep--alertness cycle, cannot be recommended for manned space missions. Good health condition and high work capacity of cosmonauts can be maintained, only if a 24-hour sleep--alertness cycle with a normal sleep pattern is provided.