The impact of trait anxiety and psychosocial stress on sympathetic neural control in humans
Bigalke, Jeremy Andrew
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Anxiety is highly prevalent, and while it is often adaptive, excessive stress and anxiety may predispose individuals to a heightened risk of cardiovascular disease. While excessive activity of the sympathetic nervous system (SNS) may underlie this association, direct measures of muscle sympathetic nerve activity (MSNA) indicate little, if any, alterations in resting sympathetic outflow in individuals with anxiety disorders. Assessment of the relationship between trait anxiety, MSNA, and blood pressure using a large cohort of healthy adults has not yet been conducted. Further, utilization of stress tasks within microneurographic settings that minimize the potential influence of breathing alterations, muscle movement, and other variables on the typically observed inter-individual variability in MSNA responsiveness to mental stress are needed to adequately assess the sole contribution of psychological stress on sympathetic neural activity. In Study 1, the association between trait anxiety, MSNA, and resting blood pressure was assessed in a population of 88 healthy adults, representing the largest study to date pairing trait anxiety with directly recorded sympathetic outflow to the periphery. Our findings indicate an independent relationship between trait anxiety, MSNA, and blood pressure when controlling for both age and sex. In Study 2, we utilized the trier social stress test (TSST) to assess the impact of anticipatory stress on MSNA and blood pressure in 28 healthy adults. Our findings showed that anticipatory stress is associated with increased blood pressure and reduced MSNA. Additionally, this appears to be baroreflex mediated as the magnitude of changes in blood pressure were directly proportional to reductions in MSNA, a relationship that was weakened or nonexistent during the active speech portion of the task. Lastly, anticipatory MSNA responsiveness accurately predicted reactivity to subsequent stress tasks. Together, these studies highlight a key relationship between both chronic, and acute psychological stress and anxiety on sympathoneural function in healthy adults.