Roach Gregory D, Matthews Raymond, Naweed Anjum, Kontou Thomas G, Sargent Charli
a Appleton Institute for Behavioural Science , Central Queensland University , Adelaide , Australia.
b Department of Clinical Neuroscience , Karolinska Institute , Stockholm , Sweden.
Chronobiol Int. 2018 Jun;35(6):872-883. doi: 10.1080/07420528.2018.1466801. Epub 2018 Jun 11.
Some shiftwokers in the long-haul transportation industries (i.e. road, rail, sea, air) have the opportunity to sleep in on-board rest facilities during duty periods. These rest facilities are typically fitted with a seat with a maximum back angle to the vertical of 20°, 40°, or 90°. The aim of this study was to examine the impact of "back angle" on the quantity and quality of sleep obtained in a seat during a daytime nap. Six healthy adults (3 females aged 27.0 years and 3 males aged 22.7 years) each participated in three conditions. For each condition, participants had a 4-h sleep opportunity in a bed (02:00-06:00 h) followed by a 4-h sleep opportunity in a seat (13:00-17:00 h). The only difference between conditions was in the back angle of the seat to the vertical during the seat-based sleep periods: 20° (upright), 40° (reclined), and 90° (flat). Polysomnographic data were collected during all sleep episodes. For the seat-based sleep episodes, there was a significant effect of back angle on three of four measures of sleep quantity, i.e. total sleep time, slow-wave sleep, and rapid eye movement (REM) sleep, and three of four measures of sleep quality, i.e. latency to REM sleep, arousals, and stage shifts. In general, the quantity and quality of sleep obtained in the reclined and flat seats were better than those obtained in the upright seat. In particular, compared to the flat seat, the reclined seat resulted in similar amounts of total sleep and slow-wave sleep, but 37% less REM sleep; and the upright seat resulted in 29% less total sleep, 30% less slow-wave sleep, and 79% less REM sleep. There are two main mechanisms that may explain the results. First, it is difficult to maintain the head in a comfortable position for sleep when sitting upright, and this is likely exacerbated during REM sleep, when muscle tone is very low. Second, an upright posture increases sympathetic activity and decreases parasympathetic activity, resulting in a heightened level of physiological arousal.
一些长途运输行业（即公路、铁路、海运、空运）的轮班工作者在工作期间有机会在车载休息设施中睡觉。这些休息设施通常配备有座椅，座椅与垂直方向的最大靠背角度为20°、40°或90°。本研究的目的是考察“靠背角度”对白天小睡时在座椅上获得的睡眠数量和质量的影响。六名健康成年人（3名27.0岁女性和3名22.7岁男性）每人都参与了三种条件下的实验。对于每种条件，参与者先在床（02:00 - 06:00）上有4小时的睡眠机会，然后在座椅（13:00 - 17:00）上有4小时的睡眠机会。不同条件之间的唯一差异在于基于座椅睡眠期间座椅与垂直方向的靠背角度：20°（直立）、40°（倾斜）和90°（平躺）。在所有睡眠阶段都收集了多导睡眠图数据。对于基于座椅的睡眠阶段，靠背角度对四项睡眠数量指标中的三项，即总睡眠时间、慢波睡眠和快速眼动（REM）睡眠，以及四项睡眠质量指标中的三项，即REM睡眠潜伏期、觉醒和睡眠阶段转换，都有显著影响。一般来说，在倾斜和平躺座椅上获得的睡眠数量和质量优于直立座椅。特别是，与平躺座椅相比，倾斜座椅的总睡眠时间和慢波睡眠时间相近，但REM睡眠减少了37%；直立座椅的总睡眠时间减少了29%，慢波睡眠时间减少了30%，REM睡眠减少了79%。有两种主要机制可以解释这些结果。首先，直立坐着时很难将头部保持在舒适的睡眠位置，而在REM睡眠期间肌肉张力非常低时，这种情况可能会加剧。其次，直立姿势会增加交感神经活动并减少副交感神经活动，导致生理觉醒水平升高。
