Key result
During a second space mission, a healthy astronaut exhibited a 61.55% increase in nighttime high-frequency heart rate variability and a 22.18% decrease during daytime compared to their first mission.
Why the study?
This study was designed to examine the feasibility of analyzing heart rate variability data from repeat-flier astronauts at matching days on two separate missions to assess the effect of repeated missions on brain plasticity and psychological resilience.
Does a repeated long-duration space mission alter heart rate variability and sleep performance compared to a first mission in a healthy astronaut?
Case Report (n=1)
No
Does a repeated long-duration space mission alter heart rate variability and sleep performance compared to a first mission in a healthy astronaut?
Effect estimate: 61.55% increase
Absolute Event Rate: 557.5% vs 345.1%
p-value: p=0.0903
In an N-of-1 study, a second long-duration spaceflight was associated with improved sleep and favorable changes in heart rate variability, suggesting enhanced neural adaptation and brain plasticity.
N-of-1 HRV shifts should not change astronaut monitoring; leaves open whether repeat missions enhance nocturnal SN plasticity and daytime resilience.
This study was designed to examine the feasibility of analyzing heart rate variability (HRV) data from repeat-flier astronauts at matching days on two separate missions to assess any effect of repeated missions on brain plasticity and psychological resilience, as conjectured by Demertzi. As an example, on the second mission of a healthy astronaut studied about 20 days after launch, sleep duration lengthened, sleep quality improved, and spectral power (ms 2 ) co-varying with activity of the salience network (SN) increased at night. HF-component (0.15–0.50 Hz) increased by 61.55%, and HF-band (0.30–0.40 Hz) by 92.60%. Spectral power of HRV indices during daytime, which correlate negatively with psychological resilience, decreased, HF-component by 22.18% and HF-band by 37.26%. LF-component and LF-band, reflecting activity of the default mode network, did not change significantly. During the second mission, 24-h acrophases of HRV endpoints did not change but the 12-h acrophase of TF-HRV did (P < 0.0001), perhaps consolidating the circadian system to help adapt to space by taking advantage of brain plasticity at night and psychological resilience during daytime. While this N-of-1 study prevents drawing definitive conclusions, the methodology used herein to monitor markers of brain plasticity could pave the way for further studies that could add to the present results.
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Otsuka et al. (2023) conducted a case report in Spaceflight adaptation (n=1). Second long-duration space mission vs. First long-duration space mission was evaluated on Nighttime HF-component (0.15-0.50 Hz) of heart rate variability (ms2) (61.55% increase, p=0.0903). During a second space mission, a healthy astronaut exhibited a 61.55% increase in nighttime high-frequency heart rate variability and a 22.18% decrease during daytime compared to their first mission.
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