Center for Advanced Research in Sleep Medicine, Sacre-Coeur Hospital of Montreal, Montreal, QC, Canada.
Department of Psychology, University of Montreal, Montreal, QC, Canada.
J Biol Rhythms. 2018 Apr;33(2):192-202. doi: 10.1177/0748730418757007. Epub 2018 Feb 20.
A number of factors can contribute to a delayed sleep schedule. An important factor could be a daily profile of light exposure favoring a later circadian phase. This study aimed to compare light exposure between 14 young adults complaining of a delayed sleep schedule and 14 matched controls and to identify possible associations between habitual light exposure and circadian phase. Exposure to white and blue light was recorded with ambulatory monitors for 7 consecutive days. Participants also noted their daily use of light-emitting devices before bedtime. Endogenous circadian phase was estimated with the dim light melatonin onset (DLMO) in the laboratory. The amplitude of the light-dark cycle to which the subjects were exposed was smaller in delayed than in control subjects, and smaller amplitude was associated with a later DLMO. Smaller amplitude was due to both decreased exposure in the daytime and increased exposure at night. Total exposure to blue light, but not to white light, was lower in delayed subjects, possibly due to lower exposure to blue-rich outdoor light. Lower daily exposure to blue light was associated with a later DLMO. Timing of relative increases and decreases of light exposure in relation to endogenous circadian phase was also compared between the 2 groups. In delayed subjects, there was a relatively higher exposure to white and blue light 2 h after DLMO, a circadian time with maximal phase-delaying effect. Delayed participants also had higher exposure to light 8 to 10 h after DLMO, which occurred mostly during their sleep episode but may have some phase-advancing effects. Self-reported use of light-emitting devices before bedtime was higher in delayed than in control subjects and was associated with a later DLMO. This study suggests that individuals complaining of a delayed sleep schedule engage in light-related behaviors favoring a later circadian phase and a later bedtime.
许多因素可能导致睡眠时间表延迟。一个重要的因素可能是日常光照暴露模式有利于昼夜节律相位延迟。本研究旨在比较 14 名抱怨睡眠时间表延迟的年轻人和 14 名匹配对照者的光照暴露情况，并确定习惯性光照暴露与昼夜节律相位之间的可能关联。使用活动监测器连续 7 天记录白光和蓝光暴露情况。参与者还记录了他们睡前日常使用发光设备的情况。在实验室中，通过测定褪黑素分泌的微光起始时间（DLMO）来估计内源性昼夜节律相位。受试者暴露于明暗周期的幅度在延迟组中比在对照组中更小，而较小的幅度与 DLMO 较晚相关。较小的幅度是由于白天暴露减少和夜间暴露增加所致。在延迟组中，总蓝光暴露量较小，但白光暴露量没有减少，这可能是由于缺乏富含蓝光的户外光暴露。每日蓝光暴露量较低与 DLMO 较晚相关。还比较了两组之间与内源性昼夜节律相位相关的光照暴露的相对增加和减少的时间。在延迟组中，在 DLMO 后 2 小时，即具有最大相位延迟效应的昼夜节律时间，有相对较高的白光和蓝光暴露。延迟组参与者在 DLMO 后 8 至 10 小时也有较高的光照暴露，这主要发生在他们的睡眠时间内，但可能具有一些相位提前效应。睡前使用发光设备的自我报告在延迟组中高于对照组，并且与 DLMO 较晚相关。这项研究表明，抱怨睡眠时间表延迟的个体从事有利于昼夜节律相位延迟和晚睡的与光照相关的行为。
