Polygraph records of the sleep of four men, mean age 29, who wintered over at South Pole Station in 1967, were acquired on magnetic tape for three consecutive nights at six points in time spanning base line recordings in the United States, four sessions at South Pole, and return to the United States. From the 15 second-night records analyzed, there is indication that total sleep time varied little, but sleep onset times were increased, and percent rapid eye movement (REM) decreased significantly, while Stage 4 sleep was virtually eliminated by the sojourn in Antarctica. Slow-wave sleep had not returned six months after return to the United States. The longterm effects of chronic hypobaric hypoxia is offered as a partial explanation for stage 4 dropout.
Natani K, Shurley JT, Pierce CM, Brooks RE. Long-Term Changes in Sleep Patterns in Men on the South Polar Plateau. Arch Intern Med. 1970;125(4):655-659. doi:10.1001/archinte.1970.00310040079008