Age and sex differences in sympathetic and hemodynamic responses to hypoxia and cold pressor test

• Published in: Physiological reports Vol. 7; no. 2; pp. e13988 - n/a
• Main Authors: Miller, Amanda J., Cui, Jian, Luck, J. Carter, Sinoway, Lawrence I., Muller, Matthew D.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.01.2019; John Wiley and Sons Inc
• Subjects: Adolescent; Adult; Age Factors; Ageing and Degeneration; Autonomic Nervous System; Birth control; Blood flow; Blood pressure; Cardiovascular Physiology; Cold Temperature; Conductance; Electrodes; Female; Femoral artery; Femoral Artery - innervation; Femoral Artery - physiology; femoral blood flow; Femur; Flow velocity; Gender differences; Heart rate; Hemodynamics; Humans; Hypoxia; Hypoxia - physiopathology; Male; Metabolism; microneurography; Middle Aged; Original Research; Physiology; Sex differences; Sex Factors; Statistical analysis; Stress, Physiological - physiology; Sympathetic nerves; sympathetic nervous system; Sympathetic Nervous System - physiology; Variance analysis; vascular resistance; Vasoconstriction; Vasodilation; Vasodilation - physiology; Veins & arteries; Women; Young Adult; Young adults; vascular resistance; Blood pressure; femoral blood flow; microneurography; sympathetic nervous system; sex differences
• ISSN: 2051-817X
• DOI: 10.14814/phy2.13988

Emerging evidence suggests that sympathetic vasoconstriction is lower in young women. We hypothesized that increases in muscle sympathetic nerve activity (MSNA) during acute physiological stressors induce less vasoconstriction in young women compared to young men. Healthy young men (n = 10, 27 ± 1 years), young women (n = 12, 25 ± 1 years), and older women (n = 10, 63 ± 6 years) performed the cold pressor test (hand in ice for 2 min) and continuous hypoxia (10% O2, 90% N2) for 5 min. MSNA, femoral blood flow velocity, heart rate, and blood pressure were acquired continuously. Femoral artery diameter was obtained every minute and used to calculate femoral blood flow, and femoral vascular resistance and conductance. MSNA responses to cold pressor test (P = 0.345) and hypoxia (P = 0.969) were not different between groups. Young women had greater femoral blood flow (P = 0.002) and vascular conductance (P = 0.041) responses to cold pressor test compared with young men. The femoral blood flow response to hypoxia was not different between the two sexes but the increase in femoral flow was attenuated in older women compared with younger women (P = 0.036). These data show that young women had paradoxical vasodilation to cold pressor test. The mechanisms responsible for the attenuated sympathetic vasoconstriction or for enhanced vasodilation in young women during the CPT require further investigation. For the first time we show that young women have paradoxical vasodilation to the cold pressor test. This supports an emerging body of literature that suggests that young women have attenuated vasoconstriction or enhanced vasodilation to physiological stressors.