Seasonal changes in human sleep-wake rhythm in Antarctica and Japan

The subjects were eight men of the Japanese Antarctic Research Expedition ( average age 35.8 years), and 10 healthy people living around Kofu, Japan (2 8.9 years). They completed a sleep log for 12 to 18 months, and the sleep-w ake state was scored in 10-min epochs. Q(24) values calculated by chi (2) p eriodgram were low in the Antarctic midwinter. This means that there was di fficulty in synchronizing to a 24-h period in the Antarctic midwinter. In A ntarctica, sleep onset and offset times were delayed mostly in the midwinte r. In Japan, sleep offset time was delayed mostly around the winter solstic e.