Key result
A mental arithmetic task in astronauts elicited an average increase in mean heart rate (Δ7 ± 1 beats/min; P=0.03), with responses unchanged by microgravity during or after spaceflight.
Why the study?
Does a mental arithmetic stress task alter cardiovascular neural response in astronauts during weightlessness?
Observational (n=5)
Does a mental arithmetic stress task alter cardiovascular neural response in astronauts during weightlessness?
Mean Difference: 7
p-value: p=0.03
Mental stress elicits sympathovagal shifts toward enhanced sympathetic modulation in astronauts, but this autonomic response is not altered by microgravity during or after spaceflight.
Autonomic responses to mental stress appear preserved in microgravity; leaves open effects during longer missions or in clinical populations.
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.
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Aubert et al. (2009) conducted an observational in Healthy astronauts (n=5). Mental arithmetic stress task vs. 10-minute resting control condition was evaluated on Change in mean heart rate (MD 7, p=0.03). A mental arithmetic task in astronauts elicited an average increase in mean heart rate (Δ7 ± 1 beats/min; P=0.03), with responses unchanged by microgravity during or after spaceflight.
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