Changes in heart rate variability during vasomotor symptoms among midlife women.

Objective: Most midlife women report vasomotor symptoms (VMS), yet their physiology remains poorly understood. This study tested whether acute decreases in cardiac vagal control would occur with VMS in a large sample of women monitored during wake and sleep.

Methods: Two hundred and fifteen nonsmoking women aged 40 to 60 years with evidence of VMS were included. Women were free of a history of clinical cardiovascular disease or arrhythmia; or use of insulin, beta blockers, calcium channel blockers, or medications impacting VMS. Women underwent 24 hours of ambulatory monitoring for physiological (sternal skin conductance) and self-report (electronic diary) measurement of VMS; heart rate variability (electrocardiogram); and respiratory rate. Changes in cardiac vagal control as assessed by respiratory sinus arrhythmia during VMS, relative to periods before and after VMS, were tested in linear mixed models.

Results: Significant decreases in respiratory sinus arrhythmia were observed during physiologically measured VMS relative to periods preceding (b[SE] = 0.13 (0.004), P < 0.0001) and after the vasomotor symptoms (b[SE] = 0.13 (0.004), P < 0.0001), adjusted for age, race, body mass index, and sleep/wake status. Decreases were observed for women not aware of their VMS, and differences persisted controlling for respiration rate. Interactions indicated that respiratory sinus arrhythmia decreases were most pronounced during sleep and for younger women.

Conclusions: Physiologically measured VMS were accompanied by an inhibition of cardiac vagal control in a large sample of women. Changes were observed irrespective of whether the VMS were reported, were most pronounced during sleep, and were greatest among younger women. These findings contribute to the understanding of vasomotor symptom physiology.