长期暴露在太空微重力环境下会改变宇航员心率变异性的时间结构。
Long-term exposure to space's microgravity alters the time structure of heart rate variability of astronauts.
作者信息
Otsuka Kuniaki, Cornelissen Germaine, Furukawa Satoshi, Kubo Yutaka, Hayashi Mitsutoshi, Shibata Koichi, Mizuno Koh, Aiba Tatsuya, Ohshima Hiroshi, Mukai Chiaki
机构信息
Executive Medical Center, Totsuka Royal Clinic, Tokyo Women's Medical University, Tokyo, Japan; Halberg Chronobiology Center, University of Minnesota, Minneapolis, MN, USA.
Halberg Chronobiology Center, University of Minnesota, Minneapolis, MN, USA.
出版信息
Heliyon. 2016 Dec 19;2(12):e00211. doi: 10.1016/j.heliyon.2016.e00211. eCollection 2016 Dec.
BACKGROUND
Spaceflight alters human cardiovascular dynamics. The less negative slope of the fractal scaling of heart rate variability (HRV) of astronauts exposed long-term to microgravity reflects cardiovascular deconditioning. We here focus on specific frequency regions of HRV.
METHODS
Ten healthy astronauts (8 men, 49.1 ± 4.2 years) provided five 24-hour electrocardiographic (ECG) records: before launch, 20.8 ± 2.9 (ISS01), 72.5 ± 3.9 (ISS02) and 152.8 ± 16.1 (ISS03) days after launch, and after return to Earth. HRV endpoints, determined from normal-to-normal (NN) intervals in 180-min intervals progressively displaced by 5 min, were compared in space versus Earth. They were fitted with a model including 4 major anticipated components with periods of 24 (circadian), 12 (circasemidian), 8 (circaoctohoran), and 1.5 (Basic Rest-Activity Cycle; BRAC) hours.
FINDINGS
The 24-, 12-, and 8-hour components of HRV persisted during long-term spaceflight. The 90-min amplitude became about three times larger in space (ISS03) than on Earth, notably in a subgroup of 7 astronauts who presented with a different HRV profile before flight. The total spectral power (TF; p < 0.05) and that in the ultra-low frequency range (ULF, 0.0001-0.003 Hz; p < 0.01) increased from 154.9 ± 105.0 and 117.9 ± 57.5 msec (before flight) to 532.7 ± 301.3 and 442.4 ± 202.9 msec (ISS03), respectively. The power-law fractal scaling β was altered in space, changing from -1.087 ± 0.130 (before flight) to -0.977 ± 0.098 (ISS01), -0.910 ± 0.130 (ISS02), and -0.924 ± 0.095 (ISS03) (invariably p < 0.05).
INTERPRETATION
Most HRV changes observed in space relate to a frequency window centered around one cycle in about 90 min. Since the BRAC component is amplified in space for only specific HRV endpoints, it is likely to represent a physiologic response rather than an artifact from the International Space Station (ISS) orbit. If so, it may offer a way to help adaptation to microgravity during long-duration spaceflight.
背景
太空飞行会改变人体心血管动力学。长期暴露于微重力环境下的宇航员，其心率变异性（HRV）分形标度的负斜率减小，反映了心血管功能失调。我们在此关注HRV的特定频率区域。
方法
10名健康宇航员（8名男性，年龄49.1±4.2岁）提供了5份24小时心电图（ECG）记录：发射前、发射后20.8±2.9（国际空间站任务1期，ISS01）、72.5±3.9（国际空间站任务2期，ISS02）和152.8±16.1（国际空间站任务3期，ISS03）天，以及返回地球后。从逐次正常心动周期（NN）间期以5分钟的步长逐步移动的180分钟间期内确定HRV终点，并在太空和地球条件下进行比较。这些数据拟合了一个模型，该模型包括4个主要预期成分，周期分别为24（昼夜节律）、12（半日节律）、8（八小时节律）和1.5（基本休息-活动周期；BRAC）小时。
研究结果
HRV的24小时、12小时和8小时成分在长期太空飞行期间持续存在。在太空（ISS03）中，90分钟振幅比在地球上大约大三倍，特别是在飞行前呈现不同HRV特征的7名宇航员亚组中。总频谱功率（TF；p<0.05）和超低频范围（ULF，0.0001 - 0.003 Hz；p<0.01）的功率分别从飞行前的154.9±105.0和117.9±57.5毫秒增加到ISS03时的532.7±301.3和442.4±202.9毫秒。幂律分形标度β在太空中发生了变化，从飞行前的-1.087±0.130变为ISS01时的-0.977±0.098、ISS02时的-0.910±0.130和ISS03时的-0.924±0.095（均p<0.05）。
解读
在太空中观察到的大多数HRV变化与以约90分钟一个周期为中心的频率窗口有关。由于BRAC成分仅在太空中针对特定的HRV终点被放大，它可能代表一种生理反应而非来自国际空间站（ISS）轨道的伪迹。如果是这样，它可能提供一种帮助在长期太空飞行中适应微重力的方法。
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