Menopausal hot flashes and the default mode network.

OBJECTIVE: To test whether more physiologically assessed hot flashes were associated with more connectivity in the default mode network (DMN), the network of brain regions active during rest. We particularly focus on DMN networks supporting the hippocampus as this region is rich in estrogen (E) receptors (ER) and has previously been linked to hot flashes.
DESIGN: Women underwent 24 hours of physiologic and diary hot flash monitoring, functional magnetic resonance imaging (MRI), 72 hours of sleep actigraphy monitoring, a blood draw, questionnaires, and physical measures.
SETTING: University medical center. PATIENT(S): Twenty midlife women aged 40-60 years who had their uterus and both ovaries and were not taking hormone therapy (HT). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The DMN functional connectivity. RESULT(S): Controlling for age, race, and education, more physiologically-monitored hot flashes were associated with greater DMN connectivity (beta, B [SE] = 0.004 [0.002]), particularly hippocampal DMN connectivity (B [SE] = 0.005 [0.002]). Findings were most pronounced for sleep physiologic hot flashes (with hippocampal DMN, B [SE] = 0.02 [0.007]). Associations also persisted controlling for sleep, depressive symptoms, and serum E2 concentrations. CONCLUSION(S): More physiologically-monitored hot flashes were associated with more DMN connectivity, particularly networks supporting the hippocampus. Findings were most pronounced for sleep hot flashes. Findings underscore the importance of continued investigation of the central nervous system in efforts to understand this classic menopausal phenomenon.