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Association between vasomotor hot flashes and heart rate variability in recently postmenopausal women

Objective: The aim of this study was to investigate whether cardiovascular autonomic reactivity and risk profile are associated with the frequency and severity of hot flashes in recently postmenopausal women. Methods: A total of 150 postmenopausal women with varying degrees of severity of hot flashes (none, mild, moderate, or severe) underwent 24-hour electrocardiographic recording. The function of the autonomic nervous system was assessed via heart rate variability in time and frequency domains. The effects of hot flashes on cardiac autonomic function were studied by assessing heart rate variability in the presence and absence of symptoms. Results: There were no differences in mean heart rate, heart rate extremes, or total number of ectopic beats between women without and women with mild, moderate, or severe hot flashes. However, most women (14/17, 82%) with frequent ventricular ectopic beats and all women with ventricular runs belonged to the symptomatic groups. Although there were no differences in 24-hour or nighttime heart rate variability between the study groups, the very-low-frequency spectral component of heart rate variability increased by 72% (P < 0.001) during the hot flash period compared with the control period and was accompanied by an increase in heart rate (3%; P < 0.001). Conclusions: Cardiovascular risk markers based on heart rate variability failed to show an association with the frequency and severity of hot flashes in recently postmenopausal women. However, during a hot flash episode, there were signs of altered autonomic control of heart rate, which may be involved in the regulatory mechanisms of hot flashes.