Disturbances of the circadian sleep-wake rhythm after time zone changes.

Studies on the changes in circadian rhythms due to time zone changes were described with emphasis placed on sleep. The results were summarized as follows. Eastward flights; Decrease of total sleep time, or increase of TST, Disturbances of intra-sleep cycles, Increase of slow wave sleep, Decrease of REM sleep in the amount, Prolonged REM sleep latency. Westward flights; Shortened sleep latency, Shortened REM sleep latency, Increase of percentage REM sleep, Unusual temporal distributions of REM sleep periods. Southward flight; No significant change. From all above mentioned it becomes evident that after transmeridian flight sleep rhythm is clearly disturbed. In this time we emphasized the changes in particular sleep stages rather than the overall changes in sleep-wake cycles. The changes in sleep pattern followed by time zone changes, however, are thought to result from a complicated summation of effects, such as sleep deprivation, sleep reversal, naps, shift in sleep onset time, and circadian rhythm alternation. The possible factors about the changes in sleep will be presented by Dr. Endo in the next lecture.