Lack of sleep disturbance from menopausal hot flashes

To determine whether hot flashes produce disordered sleep in symptomatic postmenopausal women.

Controlled laboratory study.

Healthy volunteers in a university medical center.

Symptomatic and asymptomatic postmenopausal women and premenopausal women, all of similar ages (46-51 years).

None.

Sleep electroencephalogram recordings, sternal skin conductance to record hot flashes, multiple sleep latency test to assess sleepiness, simple and divided attention performance tests, sleep and fatigue questionnaires.

Nineteen women were not selected for the following reasons: seven failed the drug screen, two had sleep apnea and periodic limb movements, one had periodic limb movements alone, two had body mass index (BMI) >30, one had hypertension, and six asymptomatic women had hot flashes in the laboratory. There were no significant group differences on any sleep stage measure. For example, for cycling vs. symptomatic vs. asymptomatic women: total sleep time, 6.9 +/- 0.7, 7.0 +/- 0.4, 7.0 +/- 0.4 hours; percentage stage 1 (light) sleep, 9.3% +/- 4.2%, 10.4% +/- 2.5%, 10.5% +/- 3.9%; number of brief arousals, 89.6 +/- 30.1, 111.9 +/- 45.8, 99.4 +/- 22.2; number of awakenings, 4.8 +/- 3.3, 6.7 +/- 2.1, 6.9 +/- 3.5. An average of 5.2 +/- 2.9 (+/-SD, range 1-18) hot flashes/night occurred in the symptomatic women. Of arousals occurring within 2 minutes of a hot flash, 46.7% occurred before, 46.7% occurred after, and 5.6% occurred simultaneously. Of awakenings occurring within 2 minutes of a hot flash, 55.2% occurred before, 40.0% after, and 5% simultaneously. There were no significant group differences on the multiple sleep latency test or any performance test or questionnaire measure.

These data provide no evidence that hot flashes produce sleep disturbance in symptomatic postmenopausal women. Previous reports of increased sleep disturbance at menopause may be due to disorders that were screened out, such as sleep apnea and drug use.