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 (r² = 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”).

中文翻译：

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生活在现实世界环境中的年轻人在几个月内的褪黑激素昼夜节律阶段、睡眠指标和时间表的稳健稳定性

行为时间与生物钟的适当同步和充足的睡眠对于几乎每个生理过程都很重要。相对于社会（即本地）时钟时间和睡眠时间的生物钟时间在个体之间可能有很大差异。这些过程的时间在个体内部是否稳定尚不清楚。我们在一所大学的 15 名学生中检查了昼夜节律控制的褪黑激素时间、睡眠时间及其在约 100 天内的相互作用的稳定性。在相隔约 35 天的三个时间点，从微光褪黑激素发作 (DLMO) 确定昼夜节律时间。通过活动记录仪确定睡眠行为（时间和持续时间）和时间类型（即，在空闲日的中间睡眠时间校正在学校/工作日的睡眠不足），并在约 1 个月的时间段内进行分析。褪黑激素时间稳定，通过组内相关系数确定几乎完美的关系强度（[ICC]=0.85）；所有参与者的平均 DLMO 时间仅在第 2 个月和第 3 个月从第一个月变化了 21 分钟和 5 分钟。睡眠行为也表现出高度稳定性，ICC 关系强度从实质性到几乎完美（ICC = 0.65-0.85）。平均 DLMO 与平均表型显着相关（r ICC 关系强度从实质性到几乎完美（ICC = 0.65-0.85）。平均 DLMO 与平均表型显着相关（r ICC 关系强度从实质性到几乎完美（ICC = 0.65-0.85）。平均 DLMO 与平均表型显着相关（r²  = 0.53, P  <.01)，表型在几个月内表现出基本稳定 (ICC = 0.61)。这些发现生活在现实环境中的年轻人的褪黑激素时间和睡眠行为具有很强的稳定性，这有望更好地理解以前的横断面报告的可靠性，以及未来对抗昼夜节律相关疾病和受损的个体化策略。安全性（即“时间医学”）。