Flynn-Evans Erin E, Barger Laura K, Kubey Alan A, Sullivan Jason P, Czeisler Charles A
Department of Medicine, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA, USA.
Department of Medicine, Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA.
NPJ Microgravity. 2016 Jan 7;2:15019. doi: 10.1038/npjmgrav.2015.19. eCollection 2016.
Sleep deficiency and the use of sleep-promoting medication are prevalent during spaceflight. Operations frequently dictate work during the biological night and sleep during the biological day, which contribute to circadian misalignment. We investigated whether circadian misalignment was associated with adverse sleep outcomes before (preflight) and during spaceflight missions aboard the International Space Station (ISS). Actigraphy and photometry data for 21 astronauts were collected over 3,248 days of long-duration spaceflight on the ISS and 11 days prior to launch (=231 days). Sleep logs, collected one out of every 3 weeks in flight and daily on Earth, were used to determine medication use and subjective ratings of sleep quality. Actigraphy and photometry data were processed using Circadian Performance Simulation Software to calculate the estimated endogenous circadian temperature minimum. Sleep episodes were classified as aligned or misaligned relative to the estimated endogenous circadian temperature minimum. Mixed-effects regression models accounting for repeated measures were computed by data collection interval (preflight, flight) and circadian alignment status. The estimated endogenous circadian temperature minimum occurred outside sleep episodes on 13% of sleep episodes during preflight and on 19% of sleep episodes during spaceflight. The mean sleep duration in low-Earth orbit on the ISS was 6.4±1.2 h during aligned and 5.4±1.4 h (<0.01) during misaligned sleep episodes. During aligned sleep episodes, astronauts rated their sleep quality as significantly better than during misaligned sleep episodes (66.8±17.7 vs. 60.2±21.0, <0.01). Sleep-promoting medication use was significantly higher during misaligned (24%) compared with aligned (11%) sleep episodes (<0.01). Use of any medication was significantly higher on days when sleep episodes were misaligned (63%) compared with when sleep episodes were aligned (49%; <0.01). Circadian misalignment is associated with sleep deficiency and increased medication use during spaceflight. These findings suggest that there is an immediate need to deploy and assess effective countermeasures to minimize circadian misalignment and consequent adverse sleep outcomes both before and during spaceflight.
睡眠不足和使用助眠药物在太空飞行期间很普遍。飞行任务常常要求在生物夜间工作，在生物白天睡眠，这导致昼夜节律失调。我们调查了在国际空间站（ISS）执行太空飞行任务前（飞行前）和飞行期间，昼夜节律失调是否与不良睡眠结果相关。在国际空间站上21名宇航员的3248天长期太空飞行期间以及发射前11天（共231天）收集了活动记录仪和光度测量数据。飞行期间每3周收集一次、在地球上每天收集一次的睡眠日志，用于确定药物使用情况和睡眠质量的主观评分。使用昼夜节律性能模拟软件处理活动记录仪和光度测量数据，以计算估计的内源性昼夜节律温度最低点。睡眠时段相对于估计的内源性昼夜节律温度最低点被分类为对齐或失调。通过数据收集间隔（飞行前、飞行期间）和昼夜节律对齐状态，计算考虑重复测量的混合效应回归模型。估计的内源性昼夜节律温度最低点在飞行前13%的睡眠时段以及太空飞行期间19%的睡眠时段出现在睡眠时段之外。在国际空间站近地轨道上，对齐睡眠时段的平均睡眠时间为6.4±1.2小时，失调睡眠时段的平均睡眠时间为5.4±1.4小时（<0.01）。在对齐睡眠时段，宇航员对睡眠质量的评分明显高于失调睡眠时段（66.8±17.7对60.2±21.0，<0.01）。与对齐睡眠时段（11%）相比，失调睡眠时段（24%）使用助眠药物的比例明显更高（<0.01）。睡眠时段失调的日子（63%）使用任何药物的比例明显高于睡眠时段对齐的日子（49%；<0.01）。昼夜节律失调与太空飞行期间的睡眠不足和药物使用增加有关。这些发现表明，迫切需要部署和评估有效的对策，以尽量减少飞行前和飞行期间的昼夜节律失调以及随之而来的不良睡眠结果。
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