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sleep-test Sleep has only recently been scientifically studied because it was always considered merely a state of decreased activity. Only since the beginning of this century have studies revealed sleep to be an extremely active state in which some parts of the body are relatively dormant, while other parts are extremely active. Adapted to the day/night cycle, many bodily functions are subject to a 24 hour rhythm, for example, body temperature, hormone production, gastric acid production and bile production, blood pressure, heartbeat etc. Also the sleep/awake rhythm is adapted to the day/night cycle by the adult person. Moreover, there exist other shorter periodic cycles which influence the conscious (awake) state. For example, during the afternoon the body is put into a state of rest which correlates the second sleep phase. In the southern countries the afternoon quiet hour (siesta) belongs to everyday life. In
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