School of Health and Biomedical Sciences, RMIT University, Melbourne, VIC, Australia.
Inner Eastern Psychology, Melbourne, VIC, Australia.
Sleep. 2024 Sep 9;47(9). doi: 10.1093/sleep/zsae087.
Current evidence suggests that cortisol levels are bi-directionally associated with sleep. However, the daily, naturalistic cortisol-sleep associations remain unclear, as current evidence is mostly cross-sectional. This study tested whether pre-sleep cortisol predicts sleep duration and quality, and whether these sleep parameters predict the following day's diurnal cortisol slope using a 15-day intensive longitudinal design with electroencephalographic measures and saliva sampling.
Ninety-five young adults (Mage = 20.48 ± 1.59 years) provided saliva samples at awakening and pre-sleep over 14 consecutive days, providing 2345 samples (85% viable). The Z-Machine Insight + was used to record over 900 nights of total sleep time (TST) and sleep efficiency (SE). Multilevel models tested these data at the between- and within-person levels.
Higher pre-sleep cortisol predicted shorter TST (p < .001) and lower SE (p < .001) at the within-person level. Individuals with shorter average TST (p = .007) or lower average SE (p < .001) had flatter diurnal cortisol slopes, compared to those with longer average TST or higher average SE. Follow-up analyses showed that individuals with shorter average TST (vs. longer average TST) had higher pre-sleep cortisol levels (p = .01).
Our findings provide evidence that pre-sleep cortisol is associated with sleep duration and quality at the within-individual level. Furthermore, individuals with short or poor sleep had flatter diurnal cortisol slopes. Although the effect sizes are small, these findings show the naturalistic associations between sleep and cortisol in a relatively healthy sample. These findings suggest that sleep maintains the regulation of the stress-response system, which is protective against mental and physical disorders.
目前的证据表明，皮质醇水平与睡眠呈双向相关。然而，目前的证据主要是横断面研究，因此，关于自然状态下皮质醇与睡眠的关联仍不清楚。本研究采用 15 天的密集纵向设计，结合脑电图测量和唾液采样，测试了睡前皮质醇是否可以预测睡眠持续时间和质量，以及这些睡眠参数是否可以预测次日的日间皮质醇斜率。
95 名年轻成年人（平均年龄 20.48±1.59 岁）在 14 天的连续时间内，每天在醒来和睡前采集唾液样本，共采集 2345 个样本（85%有效）。使用 Z-Machine Insight+记录了超过 900 个总睡眠时间（TST）和睡眠效率（SE）的夜晚。多层次模型在个体间和个体内水平上对这些数据进行了测试。
个体在睡前皮质醇水平较高，在个体内水平上预测总睡眠时间（TST）较短（p<0.001）和睡眠效率（SE）较低（p<0.001）。与平均 TST 较长或 SE 较高的个体相比，平均 TST 较短（p=0.007）或 SE 较低（p<0.001）的个体日间皮质醇斜率更平坦。后续分析表明，与平均 TST 较长的个体相比，平均 TST 较短的个体睡前皮质醇水平更高（p=0.01）。
我们的研究结果提供了证据，表明个体在个体内水平上，睡前皮质醇与睡眠持续时间和睡眠质量有关。此外，睡眠较短或较差的个体日间皮质醇斜率更平坦。尽管效应大小较小，但这些发现显示了相对健康样本中睡眠和皮质醇之间的自然关联。这些发现表明，睡眠有助于维持应激反应系统的调节，从而预防精神和身体疾病。
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