The menstrual cycle in a human female under social and temporal isolation is not coupled to the circadian rhythm in sleep-wakefulness

Abstract

We investigated the circadian rhythm in sleep-wake fulness (SW rhythm) and in the rectal-temperature profile (Temp rhythm) of a 24-year-old female subject under conditions of social and temporal isolation. The subject stayed in the isolation facility, fitted with basic living amenities but devoid of time cues, for 35 days. In isolation the Temp rhythm of the subject freer an with a period of 25.1 ± 0.8 h, but her SW rhythm freeran with a period of 45.9 ± 2.1 h (circabklian), resulting in de-synchronization of the two rhythms. In 35 calendar days the subject experienced only 22 subjective, sleep-wake-fulness days. Interestingly the menstrual £ycle of this subject was normal, i.e. two episodes of onset of menses occurred 28 calendar days apart. We conclude in this first report on the subject that the menstrual cycle in the human female may not be coupled to the circadian rhythm underlying sleep-wakefulness while under social and temporal isolation.