THE THERMOREGULATORY EFFECTS OF MENOPAUSAL HOT FLASHES ON SLEEP

Menopausal hot flashes are thought to be a disorder of thermoregulatio n initiated centrally within the medial preoptic area of the hypothala mus. These heat-loss mechanisms appear to be activated in the presence of normal core body temperature. Previous studies have demonstrated t hat thermal stimuli have the potential to alter sleep stages. We perfo rmed 24-hour ambulatory recordings of hot flashes and all-night sleep parameters on 12 postmenopausal women with hot flashes and seven postm enopausal women without flashes to determine whether the presence of h ot flashes prior to sleep or during sleep itself would result in alter ations in sleep pattern. The results show that hot hashes are associat ed with increased Stage 4 sleep and a shortened first rapid eye moveme nt period. Hot flashes occurring in the 2 hours prior to sleep onset w ere positively correlated with the amount of slow-wave sleep. The cent ral, thermoregulatory mechanism underlying hot hashes may affect hypno genic pathways inducing sleep and heat loss in the absence of a therma l load.