Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, MA, USA.
Division of Sleep Medicine, Department of Medicine, Harvard Medical School, Boston, MA, USA.
J Pineal Res. 2021 Apr;70(3):e12720. doi: 10.1111/jpi.12720. Epub 2021 Feb 16.
Appropriate synchronization of the timing of behaviors with the circadian clock and adequate sleep are both important for almost every physiological process. The timing of the circadian clock relative to social (ie, local) clock time and the timing of sleep can vary greatly among individuals. Whether the timing of these processes is stable within an individual is not well-understood. We examined the stability of circadian-controlled melatonin timing, sleep timing, and their interaction across ~ 100 days in 15 students at a single university. At three time points ~ 35-days apart, circadian timing was determined from the dim-light melatonin onset (DLMO). Sleep behaviors (timing and duration) and chronotype (ie, mid-sleep time on free days corrected for sleep loss on school/work days) were determined via actigraphy and analyzed in ~ 1-month bins. Melatonin timing was stable, with an almost perfect relationship strength as determined via intraclass correlation coefficients ([ICC]=0.85); average DLMO timing across all participants only changed from the first month by 21 minutes in month 2 and 5 minutes in month 3. Sleep behaviors also demonstrated high stability, with ICC relationship strengths ranging from substantial to almost perfect (ICCs = 0.65-0.85). Average DLMO was significantly associated with average chronotype (r = 0.53, P <.01), with chronotype displaying substantial stability across months (ICC = 0.61). These findings of a robust stability in melatonin timing and sleep behaviors in young adults living in real-world settings holds promise for a better understanding of the reliability of previous cross-sectional reports and for the future individualized strategies to combat circadian-associated disease and impaired safety (ie, "chronomedicine").
行为与生物钟的时间同步以及充足的睡眠对于几乎所有生理过程都很重要。生物钟相对于社会（即本地）时钟时间和睡眠时间的时间可以在个体之间有很大差异。这些过程在个体内部的时间是否稳定尚不清楚。我们在一所大学的 15 名学生中，检查了大约 100 天内生物钟控制的褪黑素时间、睡眠时间及其相互作用的稳定性。在相隔约 35 天的三个时间点，通过暗光褪黑素起始（DLMO）确定生物钟时间。通过运动活动记录仪确定睡眠行为（时间和持续时间）和昼夜类型（即，在有睡眠损失的上学/工作日校正后的自由日的睡眠中点），并以大约 1 个月的时间段进行分析。褪黑素时间具有很高的稳定性，其强度几乎通过组内相关系数（ICC）确定为 0.85；所有参与者的平均 DLMO 时间在第二个月仅改变了 21 分钟，在第三个月改变了 5 分钟。睡眠行为也表现出高度的稳定性，ICC 关系强度从实质性到几乎完美（ICC 0.65-0.85）。平均 DLMO 与平均昼夜类型显著相关（r 0.53，P <.01），昼夜类型在几个月内具有实质性的稳定性（ICC 0.61）。这些在现实生活环境中生活的年轻人中褪黑素时间和睡眠行为的稳定发现，为更好地理解以前的横断面报告的可靠性提供了希望，并为未来针对与生物钟相关的疾病和受损安全（即“chronomedicine”）的个体化策略提供了希望。
