Journal
HYPERTENSION
Volume 77, Issue 5, Pages 1456-1468Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/HYPERTENSIONAHA.121.16490
Keywords
aging; blood pressure; heart rate; incidence; sleep apnea; sympathetic nervous system
Categories
Funding
- Ontario Ministry of Health
- Heart and Stroke Foundation of Ontario
- Medical Research Council
- Canadian Institutes for Health Research
- Canada Research Chairs Program
- University of Toronto
- Mount Sinai Hospital Departments of Medicine
- Toronto General Hospital Research Institute
- Ted Rogers Centre for Heart Research
- Heart and Stroke Foundation Canada
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Research on muscle sympathetic nerve activity has shown that it increases with age, sleep fragmentation, and obstructive sleep apnea, with differences in patterns between men and women. While sympathetic nerve activity burst incidence is linked to hypertension, women's sympathetic nerve traffic can increase significantly without causing high blood pressure. Therefore, increased sympathetic nerve activity may be a contributing factor to hypertension, but is not always sufficient to cause hypertension.
Multiunit recordings of postganglionic sympathetic outflow to muscle yield otherwise imperceptible insights into sympathetic neural modulation of human vascular resistance and blood pressure. This Corcoran Lecture will illustrate the utility of microneurography to investigate neurogenic cardiovascular regulation; review data concerning muscle sympathetic nerve activity of women and men with normal and high blood pressure; explore 2 concepts, central upregulation of muscle sympathetic outflow and cortical autonomic neuroplasticity; present sleep apnea as an imperfect model of neurogenic hypertension; and expose the paradox of sympathetic excitation without hypertension. In awake healthy normotensive individuals, resting muscle sympathetic nerve activity increases with age, sleep fragmentation, and obstructive apnea. Its magnitude is not signaled by heart rate. Age-related changes are nonlinear and differ by sex. In men, sympathetic nerve activity increases with age but without relation to their blood pressure, whereas in women, both rise concordantly after age 40. Mean values for muscle sympathetic nerve activity burst incidence are consistently higher in cohorts with hypertension than in matched normotensives, yet women's sympathetic nerve traffic can increase 3-fold between ages 30 and 70 without causing hypertension. Thus, increased sympathetic nerve activity may be necessary but is insufficient for primary hypertension. Moreover, its inhibition does not consistently decrease blood pressure. Despite a half-century of microneurographic research, large gaps remain in our understanding of the content of the sympathetic broadcast from brain to blood vessel and its specific individual consequences for circulatory regulation and cardiovascular, renal, and metabolic risk.
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