Mitchell P J, Hoese E K, Liu L, Fogg L F, Eastman C I
Biological Rhythms Research Laboratory, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL 60612, USA.
J Biol Rhythms. 1997 Feb;12(1):5-15. doi: 10.1177/074873049701200103.
This simulated night shift field study compared high-intensity ("bright") light exposures designed to either facilitate or conflict with adaptation to a 9-h phase shift of the sleep/dark schedule. There were 7 days of baseline with night sleep followed by 8 night shifts with day sleep in a 2 x 2 design with factors bright light (facilitating vs. conflicting) and direction of shifted sleep/dark (delayed vs. advanced). A total of 32 subjects (8 in each group) were exposed to 3 h of bright light (about 5,000 lux) and 5 h of ordinary indoor room light of "dim" light (< 500 lux) during each 8-h night shift. The bright light was timed according to the light phase-response curve (PRC) to delay or advance rhythms; it was timed to occur either before or after the baseline body temperature minimum, which served as an estimate of the PRC crossover point between delays and advances. Core body temperature was measured continuously and demasked to determine daily temperature minima. Significantly more subjects showed large temperature rhythm phase shifts (> or = 6 h during the last 4 night shifts relative to baseline) with facilitating bright light compared to conflicting bright light as well as with delayed sleep/dark compared to advanced sleep/dark. The combination of facilitating bright light and delayed sleep/dark produced large phase delay shifts in all subjects tested. By contrast, the combination of conflicting bright light and advanced sleep/dark resulted in very small phase shifts in most subjects. Because bright light timed to delay usually was not able to phase shift rhythms when sleep/dark was advanced, it appears that the timing of sleep/dark was as important as the timing of the bright light. There was a relationship between the amount of phase shift and the individual's baseline phase when sleep/dark was delayed. Larger phase delays were achieved by subjects with later baseline temperature minima and greater eveningness on the Morningness-Eveningness Questionnaire. These results show that it is important to time bright light appropriately to achieve circadian adaptation to the night shift and that individual differences play an important role in the ability of the circadian system to phase shift.
这项模拟夜班的现场研究比较了高强度（“明亮”）光照，这些光照旨在促进或干扰对睡眠/黑暗时间表9小时相位偏移的适应。先有7天的夜间睡眠基线期，随后是8个夜班的白天睡眠期，采用2×2设计，因素包括明亮光照（促进与干扰）以及睡眠/黑暗的偏移方向（延迟与提前）。在每个8小时的夜班期间，共有32名受试者（每组8人）接受3小时的明亮光照（约5000勒克斯）和5小时的普通室内“昏暗”光照（<500勒克斯）。明亮光照根据光相位响应曲线（PRC）进行定时，以延迟或提前节律；它被安排在基线体温最低点之前或之后发生，基线体温最低点用作PRC延迟和提前之间交叉点的估计值。连续测量核心体温并去除掩码以确定每日体温最低点。与干扰性明亮光照相比，以及与提前睡眠/黑暗相比，接受促进性明亮光照的受试者在最后4个夜班期间相对于基线出现大的体温节律相位偏移（>或=6小时）的人数显著更多。促进性明亮光照和延迟睡眠/黑暗的组合在所有测试受试者中产生了大的相位延迟偏移。相比之下，干扰性明亮光照和提前睡眠/黑暗的组合在大多数受试者中导致非常小的相位偏移。由于当睡眠/黑暗提前时，定时延迟的明亮光照通常无法使节律发生相位偏移，因此似乎睡眠/黑暗的时间安排与明亮光照的时间安排同样重要。当睡眠/黑暗延迟时，相位偏移量与个体的基线相位之间存在关系。基线体温最低点较晚且在晨型-夜型问卷上夜型程度较高的受试者实现了更大的相位延迟。这些结果表明，为实现对夜班的昼夜节律适应而适当安排明亮光照的时间很重要，并且个体差异在昼夜节律系统进行相位偏移的能力中起着重要作用。
