Desynchronization of Human Circadian Rhythms

Fifty human sub jects have been kept in an underground bunker in conditions of continuous illumination, each in complete isolation and without any time-telling device. Rectal temperature was recorded continuously by means of an electric thermometer, and urine samples, collected in intervals of the subjects own choice, were analyzed for excretion of water, sodium, calcium and potassium. Several systems of electric contacts served to survey the subjects general activities. All subjects showed free-running circadian rhythms, the average periods of wakefulness and sleep ranging from 23.9 to 50.0 hours. 36 subjects remained internally synchronized during the whole experiment. In 5 cases, the rhythm of activity and the rhythms of vegetative functions were synchronized in a 1: 2-ratio for parts of the experiment. 9 subjects showed different circadian frequencies in activity and in body temperature; in two of these subjects, desynchronization started immediately after being enclosed in the bunker, in the remaining 7 subjects after 9 to 23 days of confinement.