• Sleep Medicine and Psychophysiology
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• v.4 no.1
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• pp.57-65
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• 1997

As jet lag of modern travel continues to spread, there has been an exponential growth in popular explanations of jet lag and recommendations for curing it. Some of this attention are misdirected, and many of those suggested solutions are misinformed. The author reviewed the basic science of jet lag and its practical outcome. The jet lag symptoms stemed from several factors, including high-altitude flying, lag effect, and sleep loss before departure and on the aircraft, especially during night flight. Jet lag has three major components; including external de synchronization, internal desynchronization, and sleep loss. Although external de synchronization is the major culprit, it is not at all uncommon for travelers to experience difficulty falling asleep or remaining asleep because of gastrointestinal distress, uncooperative bladders, or nagging headaches. Such unwanted intrusions most likely to reflect the general influence of internal desynchronization. From the free-running subjects, the data has revealed that sleep tendency, sleepiness, the spontaneous duration of sleep, and REM sleep propensity, each varied markedly with the endogenous circadian phase of the temperature cycle, despite the facts that the average period of the sleep-wake cycle is different from that of the temperature cycle under these conditions. However, whereas the first ocurrence of slow wave sleep is usually associated with a fall in temperature, the amount of SWS is determined primarily by the length of prior wakefulness and not by circadian phase. Another factor to be considered for flight in either direction is the amount of prior sleep loss or time awake. An increase in sleep loss or time awake would be expected to reduce initial sleep latency and enhance the amount of SWS. By combining what we now know about the circadian characteristics of sleep and homeostatic process, many of the diverse findings about sleep after transmeridian flight can be explained. The severity of jet lag is directly related to two major variables that determine the reaction of the circadian system to any transmeridian flight, eg., the direction of flight, and the number of time zones crossed. Remaining factor is individual differences in resynchmization. After a long flight, the circadian timing system and homeostatic process can combine with each other to produce a considerable reduction in well-being. The author suggested that by being exposed to local zeit-gebers and by being awake sufficient to get sleep until the night, sleep improves rapidly with resynchronization following time zone change.

• Sleep Medicine and Psychophysiology
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• v.4 no.2
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• pp.156-163
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• 1997

Objectives : The authors investigated the practice of sleep hygiene and its effectiveness in general population who had experienced insomnia. If we find the items which be little practiced but especially effective, we would establish empirical an and theoretical basis to design the treatment program for insomnia, therefore apply it in clinical practice. Methods : The 226 subjects who had experienced insomnia, were at the age above 18 in Seoul, Korea. The questionnaire included the demographic data, the experience of insomnia, and the practices and effects of sleep hygiene instruction. The interview was administered face to face by the investigators. Results : The subjects reported that they practiced many of the sleep hygiene items related with arousal in sleep setting, and that those items were effective. The items such as 'get regular exercise each day(H)', 'take a hot bath(H)', 'concentrate on the pleasant feeling of relaxation(A)' were not usually practiced, but these items were reported very effective for sleep. Conclusion : The findings suggested that there were sleep hygiene items which should be educated and directed to practice actively in treatment program for insomniacs. Some items, which were especially reported low practice but highly effective, would be recommended to be studied about each therapeutic effectiveness in follow-up studies.