Study confirms drop in parasympathetic function during hot flashes

By Anne Harding

NEW YORK (Reuters Health) - Midlife women show decreases in cardiac vagal control during vasomotor symptoms (VMS), a large new study has confirmed.

"During hot flashes, women experienced significant declines in parasympathetic nervous system control of the heart," Dr. Rebecca Thurston of the University of Pittsburgh School of Medicine, one of the study's authors, explained in a telephone interview with Reuters Health. "Emerging work has started to link vasomotor symptoms to markers of cardiovascular risk, calling into question how physiologically benign these are," she added.

While more than 70% of women report hot flashes and night sweats during the menopausal transition, the physiology underlying VMS is poorly understood, Dr. Thurston and her colleagues wrote in their report, published online February 20 in Menopause. A few studies have found decreased cardiac vagal control during VMS, they added, but these studies were small and many only measured VMS during sleep.

In the current study, the researchers monitored VMS in 215 women aged 40 to 60 over a 24-hour period using sternal skin conductance, while also monitoring heart rate, heart rate variability, and respiration. About 70% of the women reported having VMS, while the rest said they had not had VMS during the previous three weeks.

The women averaged 10 physiologically detected VMS over 24 hours, seven while awake and three during sleep. There were a total of 2,386 physiologically detected VMS in all the study participants, and 958 self-reported VMS.

Respiratory sinus arrhythmia (RSA) was significantly reduced during VMS, compared to the periods before and after, Dr. Thurston and her team found. RSA declines with VMS were slightly greater during sleep.

While occasional hot flashes shouldn't raise concerns about a woman's cardiovascular health, Dr. Thurston said, very frequent hot flashes could signal cardiovascular problems. "When you have a woman who is presently reporting a lot of vasomotor symptoms, just make sure you are on top of her cardiovascular risk factors," the researcher said.

Also, she added, doctors should advise their patients that techniques that can help restore autonomic nervous system balance, such as relaxation meditation, restorative yoga, and deep breathing, may help "take the edge off" their symptoms, although there has been little research on their effectiveness.

Exercise is also likely to be helpful in managing VMS, Dr. Thurston added, because it can help improve mood and sleep.

The National Heart Lung and Blood Institute supported this research.

SOURCE: http://bit.ly/1PGfIGK

Menopause 2016.

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