SLEEP AND THE SLEEP ELECTROENCEPHALOGRAM ACROSS THE MENSTRUAL-CYCLE IN YOUNG HEALTHY WOMEN

Cyclic changes in hormones, body temperature, and metabolic rate chara cterize the menstrual cycle. To investigate whether these changes are associated with changes in sleep and the sleep electroencephalogram (E EG), a total of 138 sleep episodes from 9 women with no premenstrual s yndrome symptoms were recorded every second night throughout one ovula tory menstrual cycle and analyzed in relation to menstrual phase. Ovul ation and menstrual cycle stage were confirmed by measurements of temp erature, urinary LH, and midluteal plasma levels of estrogen and proge sterone. No significant variation across the menstrual cycle was obser ved for subjective ratings of sleep quality and mood as well as for ob jective measures of total sleep time, sleep efficiency, sleep latency, rapid eye movement sleep latency, and slow wave sleep. In nonrapid ey e movement sleep, EEG power density in the 14.25-15.0 hertz band, whic h corresponds to the upper frequency range of the sleep spindles, exhi bited a large variation across the menstrual cycle, with a maximum in the luteal phase. The data show that in healthy young women, sleep spi ndle frequency activity varies in parallel with core body temperature, whereas homeostatic sleep regulatory mechanisms, as indexed by the ti me course of EEG slow wave activity are not substantially affected by the menstrual cycle.