Circadian rhythm of objectively recorded hot flashes in postmenopausal breast cancer survivors.

ABSTRACT

OBJECTIVE: Similar to the circadian rhythm of core body temperature, hot flashes have been found to exhibit a circadian rhythm in healthy, naturally postmenopausal women, with a peak in frequency at 1825 h. However, to date, no studies have evaluated whether this same pattern is found among breast cancer survivors reporting hot flashes. DESIGN: Daily hot flash frequencies were measured among 21 postmenopausal breast cancer survivors using validated 24-h sternal skin conductance monitoring. RESULTS: Hot flashes were noted in all women, ranging in frequency from 1 to 30 per 24-h period. A majority of the sample (86%) experienced > or = 1 nighttime hot flash, with 48% exhibiting > or = 3 but < or = 7 nighttime hot flashes. For the total sample, a modest circadian rhythm was noted with a peak in hot flash frequency occurring at 1610 h. However, significant variability was observed across individual women, and, as a whole, breast cancer survivors demonstrated distorted to obliterated rhythms. CONCLUSIONS: Data suggest that hot flashes in postmenopausal breast cancer survivors do not follow the same circadian pattern as previously seen in healthy, naturally postmenopausal women. Findings have implications for (1) understanding the potential for sleep disturbances and fatigue in breast cancer survivors experiencing hot flashes, and (2) future research examining circadian rhythms of core body temperature and hot flashes in breast cancer survivors.