Effects of mental stress on autonomic cardiac modulation during weightlessness

Abstract

Sustained weightlessness affects all body functions, among these also cardiac autonomic control mechanisms. How this may influence neural response to central stimulation by a mental arithmetic task remains an open question. The hypothesis was tested that microgravity alters cardiovascular neural response to standardized cognitive load stimuli. Beat-to-beat heart rate, brachial blood pressure, and respiratory frequency were collected in five astronauts, taking part in three different short-duration (10 to 11 days) space missions to the International Space Station. Data recording was performed in supine position 1 mo before launch; at days 5 or 8 in space; and on days 1, 4, and 25 after landing. Heart rate variability (HRV) parameters were obtained in the frequency domain. Measurements were performed in the control condition for 10 min and during a 5-min mental arithmetic stress task, consisting of deducting 17 from a four-digit number, read by a colleague, and orally announcing the result. Our results show that over all sessions (pre-, in-, and postflight), mental stress induced an average increase in mean heart rate (Delta7 +/- 1 beats/min; P = 0.03) and mean arterial pressure (Delta7 +/- 1 mmHg; P = 0.006). A sympathetic excitation during mental stress was shown from HRV parameters: increase of low frequency expressed in normalized units (Delta8.3 +/- 1.4; P = 0.004) and low frequency/high frequency (Delta1.6 +/- 0.3; P = 0.001) and decrease of high frequency expressed in normalized units (Delta8.9 +/- 1.4; P = 0.004). The total power was not influenced by mental stress. No effect of spaceflight was found on baseline heart rate, mean arterial pressure, and HRV parameters. No differences in response to mental stress were found between pre-, in-, and postflight. Our findings confirm that a mental arithmetic task in astronauts elicits sympathovagal shifts toward enhanced sympathetic modulation and reduced vagal modulation. However, these responses are not changed in space during microgravity or after spaceflight.

Cardiovascular Autonomic Adaptation to Long-Term Confinement During a 105-Day Simulated Mars Mission

“…The increase in blood pressure in response to mental stress before confi nement is in line with previous studies ( 5,8,13 ). The enhancement in arterial blood pressure during mental task performance is mostly elicited by peripheral Copyright: Aerospace Medical Association a -adrenergic vascular stimulation, mediated by central activation ( 5 ). However, the response of blood pressure to mental stress showed a reversed pattern in the beginning of confi nement.…”

“…Mental stress is routinely used in autonomic function testing and commonly provokes changes in cardiac function after increased sympathetic arousal ( 28 ). The increase in blood pressure in response to mental stress before confi nement is in line with previous studies ( 5,8,13 ). The enhancement in arterial blood pressure during mental task performance is mostly elicited by peripheral Copyright: Aerospace Medical Association a -adrenergic vascular stimulation, mediated by central activation ( 5 ).…”

“…The psychological states may affect the activities in the frontal cortex and limbic system at different cognitive-emotional levels or be translated into autonomic or endocrine outputs at the hypothalamus or brain stem, which, in turn, alters cardiovascular activities ( 18 ). On the other hand, the cardiovascular responses to mental stress were not changed by acute simulated microgravity (head-down tilt test) ( 13 ) nor by short-term exposure to microgravity (10-11 d space missions) ( 5 ). The signifi cant changes observed in the present study might result from the longer duration of exposure to confi nement (3 mo).…”

Effects of real and simulated weightlessness on the cardiac and peripheral vascular functions of humans: A review

“…In earlier days, PVCs and PACs were believed to be caused by the psychological factors of the astronauts, instead of the weightlessness per se [17]. For example, PVCs experienced by 9 astronauts in 42 spaceflights between 1964 and 1985 were ascribed to the psychological stresses [18].…”

Towards human exploration of space: the THESEUS review series on cardiovascular, respiratory, and renal research priorities

“…9 In addition to these physiological factors, psychological factors (hostile environment, confinement…) elicit stress, 4,6 influencing cardiovascular function. 10 …”