Sleep and the sleep electroencephalogram across the menstrual cycle in young healthy women.

Cyclic changes in hormones, body temperature, and metabolic rate characterize the menstrual cycle. To investigate whether these changes are associated with changes in sleep and the sleep electroencephalogram (EEG), a total of 138 sleep episodes from 9 women with no premenstrual syndrome symptoms were recorded every second night throughout one ovulatory menstrual cycle and analyzed in relation to menstrual phase. Ovulation and menstrual cycle stage were confirmed by measurements of temperature, urinary LH, and midluteal plasma levels of estrogen and progesterone. No significant variation across the menstrual cycle was observed for subjective ratings of sleep quality and mood as well as for objective measures of total sleep time, sleep efficiency, sleep latency, rapid eye movement sleep latency, and slow wave sleep. In nonrapid eye movement sleep, EEG power density in the 14.25-15.0 hertz band, which corresponds to the upper frequency range of the sleep spindles, exhibited a large variation across the menstrual cycle, with a maximum in the luteal phase. The data show that in healthy young women, sleep spindle frequency activity varies in parallel with core body temperature, whereas homeostatic sleep regulatory mechanisms, as indexed by the time course of EEG slow wave activity are not substantially affected by the menstrual cycle.