Consecutive monitoring of sleep disturbance for four nights at the top of Mt Fuji (3776 m).

The purpose of the present study was to conduct consecutive monitoring of sleep from the second to the fifth night at altitude. Three healthy male subjects climbed the top of Mt Fuji (3776 m) and stayed there for 6 days. Polysomnographic recordings were performed during this period and control recordings were made at sea level 1 month after the mountaineering. Disturbed sleep characterized by an increased number of arousals and/or long wake time was observed to persist through the fifth night in all subjects. These results suggest that sleep disturbance might persist during initial days at altitude despite cumulating sleep pressure due to poor night's sleep.