Cardiovascular disease remains the leading cause of death in women, and hypertension is a major contributing factor, particularly after menopause. The sympathetic nervous system — historically viewed as the “fight or flight” part of our autonomic nervous system — is involved in regulating blood pressure (BP) and can contribute to the development of hypertension. Previous studies have shown that BP increases more in postmenopausal women during exercise compared to younger women. This exaggerated exercise-induced BP response increases cardiovascular risk in postmenopausal women, yet the underlying mechanism(s) remain unknown. Moreover, it is unclear if these exaggerated BP responses are due to aging or if they are related to declines in ovarian hormones like estradiol that are associated with menopause.
In our current study in the March 2022 issue of Medicine & Science in Sports & Exercise®, we examined the BP response during isometric handgrip exercise. We sought to determine if the large increases in BP during exercise in postmenopausal women are due to changes in the sympathetic nervous system. We directly measured sympathetic nervous system activity using a technique called microneurography. This method allows us to assess how frequently the nervous system is firing at rest and in response to isometric handgrip exercise. This measurement, along with beat-to-beat BP, was compared between young premenopausal women and postmenopausal women. We also tested a separate group of postmenopausal women before and following one month of transdermal estradiol therapy. Our data show that the sympathetic nervous system is overactive and increases to a greater extent during handgrip exercise in postmenopausal women, contributing, in part, to the larger increases in BP. However, these large increases in sympathetic nervous system activity and BP during handgrip exercise were attenuated in postmenopausal women after one month of estradiol therapy. We conclude that both aging and changes in estradiol that occur with menopause contribute to the exaggerated increases in sympathetic nervous system activity and BP during isometric exercise in postmenopausal women.
Since the release of the Women’s Health Initiative data roughly 20 years ago, numerous research studies have demonstrated that hormone therapy can be safely used by the majority of postmenopausal women. Although hormone therapy may not serve as a primary prevention to reduce the development of cardiovascular disease, it has become clear that it does not necessarily carry the risk once thought if used within established guidelines. Our data show that transdermal estradiol therapy can attenuate sympathetic nervous system activity and BP during exercise. However, in terms of primary prevention for cardiovascular disease, it is well established that exercise is a cornerstone therapy for lowering BP and improving cardiovascular health. Our data bring awareness to the importance of monitoring BP in women during physical activity while reinforcing the need to specifically consider BP in exercise-prescription guidelines for women. Notably, recent data suggest that the risk for development of cardiovascular disease begins at a lower BP threshold for women compared to men.
The inclusion of women in research is paramount for improving human health. Our findings demonstrate that studies focused on women remain important to gain a better understanding of cardiovascular disease risk in women.
Megan M. Wenner, Ph.D., is an associate professor in the Department of Kinesiology and Applied Physiology at the University of Delaware. She received a Ph.D. in physiology from the University of Delaware and completed her postdoctoral training at the John B. Pierce Laboratory and Yale School of Medicine. Dr. Wenner’s research focuses on cardiovascular health in women throughout the lifespan, with a focus on sex hormones and menopause.
Paul J. Fadel, Ph.D., is a professor in the Department of Kinesiology and associate dean for Research at the University of Texas at Arlington. Dr. Fadel’s research focuses on neural cardiovascular control mechanisms in human health and disease, with a specific emphasis on the sympathetic branch of the autonomic nervous system.
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