This study aimed to validate the association between hair cortisol and 30-day integrated salivary cortisol levels. Additionally, the intra-individual stability of the hair cortisol and the association between hair cortisol and salivary cortisol in several time domains were systematically explored. Twenty-four adults (15 men and 9 women, mean age: 22.7 ± 2.8 years) were asked to collect three saliva samples per day for 30 days, immediately after awakening (time 1), 30 min after awakening (time 2), and at bedtime (time 3). The hair sample was taken from the posterior vertex as close as possible to the scalp at the end of the 30-day study period. The area under the curve based on times 1 and 3 showed that cortisol levels in the 1 cm hair segment closest to the scalp were moderately correlated with the 30-day salivary cortisol levels (r = 0.41, p = 0.047). However, this correlation was not observed for the cortisol awakening response, diurnal slope, or other metrics in different time domains. The mean salivary cortisol at time 3 was significantly correlated with hair cortisol (r = 0.42, p = 0.041). Intra-individual stability of the hair cortisol was maintained for at least 4 months. Hair cortisol may reflect basal cortisol levels more substantially over longer periods (longer than 1 month and for at least 4 month), thus reflecting longitudinal cortisol production, rather than the day-to-day temporal cortisol response. Salivary cortisol is an ideal metric for short-term or day-to-day stress response. Researchers should select suitable metrics, such as hair cortisol for basal level (or trait) or salivary cortisol for response (or state), depending on the study objective.

中文翻译：

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头发皮质醇与昼夜基础皮质醇水平之间的关联：一项为期 30 天的验证研究

本研究旨在验证头发皮质醇与 30 天综合唾液皮质醇水平之间的关联。此外，系统地探索了头发皮质醇的个体内稳定性以及头发皮质醇和唾液皮质醇在几个时间域中的关联。要求 24 名成人（15 名男性和 9 名女性，平均年龄：22.7 ± 2.8 岁）每天收集三个唾液样本，持续 30 天，在醒来后立即（时间 1）、醒来后 30 分钟（时间 2）和在就寝时间（时间 3）。在 30 天研究期结束时，头发样本取自尽可能靠近头皮的后顶点。基于时间 1 和 3 的曲线下面积表明，最靠近头皮的 1 cm 头发段的皮质醇水平与 30 天唾液皮质醇水平呈中度相关（r = 0.41，p = 0. 047)。然而，对于皮质醇觉醒反应、昼夜斜率或不同时间域中的其他指标，并未观察到这种相关性。时间 3 的平均唾液皮质醇与头发皮质醇显着相关（r = 0.42，p = 0.041）。头发皮质醇的个体内稳定性至少维持了 4 个月。头发皮质醇可能会在更长的时间内（超过 1 个月和至少 4 个月）更显着地反映基础皮质醇水平，从而反映纵向皮质醇的产生，而不是日常的颞皮质醇反应。唾液皮质醇是衡量短期或日常压力反应的理想指标。研究人员应根据研究目标选择合适的指标，例如用于基础水平（或特征）的头发皮质醇或用于反应（或状态）的唾液皮质醇。对于皮质醇觉醒反应、昼夜斜率或不同时间域中的其他指标，未观察到这种相关性。时间 3 的平均唾液皮质醇与头发皮质醇显着相关（r = 0.42，p = 0.041）。头发皮质醇的个体内稳定性至少维持了 4 个月。头发皮质醇可能会在更长的时间内（超过 1 个月和至少 4 个月）更显着地反映基础皮质醇水平，从而反映纵向皮质醇的产生，而不是日常的颞皮质醇反应。唾液皮质醇是衡量短期或日常压力反应的理想指标。研究人员应根据研究目标选择合适的指标，例如用于基础水平（或特征）的头发皮质醇或用于反应（或状态）的唾液皮质醇。对于皮质醇觉醒反应、昼夜斜率或不同时间域中的其他指标，未观察到这种相关性。时间 3 的平均唾液皮质醇与头发皮质醇显着相关（r = 0.42，p = 0.041）。头发皮质醇的个体内稳定性至少维持了 4 个月。头发皮质醇可能会在更长的时间内（超过 1 个月和至少 4 个月）更显着地反映基础皮质醇水平，从而反映纵向皮质醇的产生，而不是日常的颞皮质醇反应。唾液皮质醇是衡量短期或日常压力反应的理想指标。研究人员应根据研究目标选择合适的指标，例如用于基础水平（或特征）的头发皮质醇或用于反应（或状态）的唾液皮质醇。