HUMAN SLEEP-WAKE CYCLES IN THE HIGH ARCTIC - EFFECTS OF UNUSUAL PHOTOPERIODICITY IN A NATURAL SETTING

Studies of human circadian rhythms are typically conducted in artifici al environments that are low in ecological validity. In the current st udy, six subjects and the field director lived in temporal isolation i n a completely natural environment with constant daylight (a high Arct ic research camp) for six weeks. Detailed daily sleep logs were kept. In keeping with past findings, five of the six subjects. developed a f ree-running sleep-wake cycle longer than 24 hours. Unlike past results , the isolated subjects did not exhibit any synchronicity in their rhy thms. There was a high degree of intersubject variability in circadian patterns. The findings have important implications for the comparison of the results of laboratory and field investigations of sleep-wake c ycles.