Klerman E B, Duffy J F, Dijk D J, Czeisler C A
Circadian, Neuroendocrine, and Sleep Disorders Section, Division of Endocrinology-Hypertension, Department of Medicine, Harvard Medical School and Brigham and Women's Hospital, Boston, Mass., USA.
J Investig Med. 2001 Jan;49(1):30-40. doi: 10.2310/6650.2001.34088.
Aging is associated with frequent complaints about earlier bedtimes and waketimes. These changes in sleep timing are associated with an earlier timing of multiple endogenous rhythms, including core body temperature (CBT) and plasma melatonin, driven by the circadian pacemaker. One possible cause of the age-related shift of endogenous circadian rhythms and the timing of sleep relative to clock time is a change in the phase-shifting capacity of the circadian pacemaker in response to the environmental light-dark cycle, the principal synchronizer of the human circadian system.
We studied the response of the circadian system of 24 older men and women and 23 young men to scheduled exposure to ocular bright light stimuli. Light stimuli were 5 hours in duration, administered for 3 consecutive days at an illuminance of approximately 10,000 lux. Light stimuli were scheduled 1.5 or 3.5 hours after the CBT nadir to induce shifts of endogenous circadian pacemaker to an earlier hour (phase advances) or were scheduled 1.5 hours before the CBT nadir to induce shifts to a later hour (phase delays). The rhythms of CBT and plasma melatonin assessed under constant conditions served as markers of circadian phase.
Bright light stimuli elicited robust responses of the circadian timing system in older people; both phase advances and phase delays were induced. The magnitude of the phase delays did not differ significantly between older and younger individuals, but the phase advances were significantly attenuated in older people.
The attenuated response to light stimuli that induce phase advances does not explain the advanced phase of the circadian pacemaker in older people. The maintained responsiveness of the circadian pacemaker to light implies that scheduled bright light exposure can be used to treat circadian phase disturbances in older people.
衰老常伴随着早睡早起的频繁抱怨。睡眠时间的这些变化与多种内源性节律的提前有关，包括由昼夜节律起搏器驱动的核心体温（CBT）和血浆褪黑素。内源性昼夜节律与相对于时钟时间的睡眠时间的年龄相关变化的一个可能原因是昼夜节律起搏器对环境明暗周期（人类昼夜节律系统的主要同步器）的相移能力发生了变化。
我们研究了24名老年男性和女性以及23名年轻男性的昼夜节律系统对定时眼部强光刺激的反应。光刺激持续5小时，在约10000勒克斯的照度下连续3天给药。光刺激安排在CBT最低点后1.5或3.5小时进行，以诱导内源性昼夜节律起搏器提前（相位提前），或安排在CBT最低点前1.5小时进行，以诱导延迟（相位延迟）。在恒定条件下评估的CBT和血浆褪黑素节律作为昼夜节律相位的标志物。
强光刺激在老年人中引发了昼夜节律系统的强烈反应；相位提前和相位延迟均被诱导。老年人和年轻人之间的相位延迟幅度没有显著差异，但老年人的相位提前明显减弱。
对诱导相位提前的光刺激反应减弱并不能解释老年人昼夜节律起搏器的提前相位。昼夜节律起搏器对光的反应性保持意味着定时强光照射可用于治疗老年人的昼夜节律相位紊乱。
