Diurnal fluctuation of sleep propensity across the menstrual cycle

Most women experience sleep changes across the menstrual cycle. We applied the ultra-short sleep-wake schedule to healthy females to compare their 24- h sleep propensity rhythms in the follicular and luteal phases. The daytime (09.00-16.30 h) subjective sleepiness and the number of slow wave sleep-co ntaining nap trials increased in the luteal phase compared to the follicula r phase, but the mean sleep propensity did not change. During the periods o f 17.00-00.30h and 01.00-08.30h there were no differences between the two p hases These results suggest that increased daytime sleepiness in the luteal phase may be related to brain mechanisms controlling slow wave sleep.