Reduced vagal activity in salt-sensitive subjects during mental challenge

• Published in: American journal of hypertension 2003-07, Vol.16 (7), p.531-536
• Main Authors: Buchholz, Konrad, Schächinger, Hartmut, Wagner, Miriam, Sharma, Arya M, Deter, Hans Christian
• Format: Article
• Language: English
• Subjects: Adult; Arterial hypertension. Arterial hypotension; Autonomic Nervous System - physiology; Autonomic Nervous System - physiopathology; Biological and medical sciences; Blood and lymphatic vessels; blood pressure; Blood Pressure - physiology; Cardiology. Vascular system; Cardiovascular Physiological Phenomena; Clinical manifestations. Epidemiology. Investigative techniques. Etiology; Electrocardiography; Heart rate variability; Humans; Male; Medical sciences; mental stress; Nervous System Physiological Phenomena; Rest - physiology; Salts - metabolism; sodium-dependent hypertension; Stress, Psychological - metabolism; Stress, Psychological - physiopathology; vagal activity; Vagus Nerve - physiology; Vagus Nerve - physiopathology
• ISSN: 0895-7061; 1879-1905; 1941-7225
• DOI: 10.1016/S0895-7061(03)00905-1

Salt-sensitive normotensive men exhibit an enhanced pressor and heart rate (HR) response to mental stress. Stress-induced HR acceleration may result from sympathetic activation or vagal withdrawal. We studied the importance of vagal withdrawal for the increased stress responsiveness of salt-sensitive subjects. We studied cardiovascular reactivity to mental challenge in 17 salt-sensitive healthy white male students and 56 salt-resistant control subjects who were comparable with respect to age, body mass index, and physical fitness. Salt sensitivity was determined by a 2-week dietary protocol (20 mmol v 240 mmol sodium/day). Mental stress was induced by a computerized information-processing task (manometer test). Electrocardiogram and finger blood pressure (BP; Finapres, Ohmeda, Louisville, CO) were registered continuously to determine HR and interbeat-interval length. Time and frequency domain (spectral power) based measures of respiratory-related heart rate variability (HRV) were calculated to estimate vagal cardiac control; diastolic BP reactivity was assessed to estimate peripheral sympathetic effects. Stress-induced increase in HR was higher in salt-sensitive than in salt-resistant subjects. Salt-sensitive subjects, in comparison to salt-resistant subjects, showed significantly reduced respiratory-related HRV during baseline and mental stress conditions ( P < .01). The increase in diastolic BP during mental challenge was significantly greater in salt-sensitive subjects ( P < .05). Our findings suggest reduced vagal and increased sympathetic tone during mental challenge in salt-sensitive subjects. Altered autonomic nervous system function may contribute to later development of hypertension in salt-sensitive individuals.