Circadian and age-related modulation of thermoreception and temperature regulation: mechanisms and functional implications

At older ages, the circadian rhythm of body temperature shows a decreased amplitude, an advanced phase, and decreased stability. The present review evaluates to what extent these changes may result from age-related deficiencies at several levels of the thermoregulatory system, including thermoreception, thermogenesis and conservation, heat loss, and central regulation. Whereas some changes are related to the aging process per se, others appear to be secondary to other factors, for which the risk increases with aging, notably a decreased level of fitness and physical activity. Moreover, functional implications of the body temperature rhythm are discussed. For example, the relation between circadian rhythm and thermoregulation has hardly been investigated, while evidence showed that sleep quality is dependent on both aspects. It is proposed that the circadian rhythm in temperature in homeotherms should not be regarded as a leftover of ectothermy in early evolution, but appears to be of functional significance for physiology from the level of molecules to cognition. A new view on the functional significance of the circadian rhythm in peripheral vasodilation and the consequent out-of-phase rhythms in skin and core temperature is presented. It is unlikely that the strong, daily occurring, peripheral vasodilation primarily represents heat loss in response to a lowering of set point, since behavioral measures are simultaneously taken in order to prevent heat loss. Several indications rather point towards a supportive role in immunological host defense mechanisms. Given the functional significance of the temperature rhythm, research should focus on the feasibility and effectiveness of methods that can in principle be applied in order to enhance the weakened circadian temperature rhythm in the elderly.     

失眠的评估

失眠是困扰许多人的最常见的睡眠问题。失眠引起白天困倦、疲劳、情绪烦恼、工作效率下降，甚至可造成致命性的结果。虽然失眠发病率很高，但大多数失眠者并未被临床医生所识别。对失眠恰当的评估对患者非常重要。本文将回顾近年来对失眠评定方面的研究，内容包括睡眠史、自评方法、心理评估，心理生理评估、医学评估、多导睡眠图及其它睡眠评估方法。     

Circadian temperature and wake rhythms of rats exposed to prolonged continuous illumination

The purpose of this study was to simultaneously measure temperature and sleep in the rat under continuous illumination in an attempt to reveal properties of the underlying circadian oscillators. At first, the circadian rhythms of temperature and wake free-ran in parallel. Within weeks or months, circadian arrhythmicity developed in most animals. Both circadian rhythms eventually damped out, even at fairly low light intensities. The circadian rhythm of wake was weaker and disintegrated sooner than the circadian rhythm of temperature. Although the data did not rule out control by separate circadian oscillators, one for temperature and one for wake, a single oscillator model was sufficient to explain this phenomenon. Ultradian variations with a period of about 2–5 hr were superimposed upon the circadian rhythms. When the circadian rhythms damped out, the ultradian variations remained. The ultradian bursts of wake preceded the ultradian bursts of temperature, suggesting a causal relationship. On the other hand, the circadian rhythm of temperature could not be dependent on the circadian rhythm of wakefulness, because the temperature rhythm could persist while the wake rhythm was absent.     

Duration and Placement of Sleep in a "Disentrained" Environment

Sleep/wake cycles of 9 young adults were electrographically recorded during 60 hrs of enforced bedrest. During this period subjects were required to lie quietly, with no time cues and minimal exogenous stimulation. Sleep and wakefulness patterns were clearly modified under these conditions. There was an alternation of waking periods with an average length of 2.7 hrs and sleep episodes with a mean duration of 2.99 hrs. Eighty percent of both sleep and waking periods were less than 4 hrs duration. The circadian pattern of sleep period duration persisted in disentrainment, but temporal organization of sleep episodes was substantially disrupted; sleep episodes occurred throughout the 24-hr day. The results suggest the presence of two distinct components of the human sleep system–one, sleep duration, is controlled by an endogenous circadian oscillatory system; another, sleep placement, is controlled primarily by behavioral controls, in the form of social and occupational pressures, and self-imposed behavioral alternatives to sleep.     

Respiratory chemoreflexes and effects of cortical activation state in urethane anesthetized rats

Urethane anesthetized (< 1 .3 g/kg), Sprague-Dawley (SD) rats spontaneously cycled between a cortically desynchronized state (State I) and a cortically synchronized state (State III), which were very similar to awake and slow wave sleep (SWS) states in unanesthetized animals, based on EEG criteria. These low levels of urethane anaesthesia did not cause significant respiratory depression or reductions in sensitivity to hypoxia (10% O2 in nitrogen) or hypercapnia (5% CO2 in air) in rats in either State I or State III. Thus, breathing frequency (fR), tidal volume (VT) and total ventilation (VTOT) all increased on cortical activation in urethane-anaesthetized rats whether breathing air, the hypoxic or the hypercapnic gas mixture, in a manner that was very similar to that observed in unanaesthetized animals. The relative sensitivity to hypoxia was greater in State III than State I, the relative sensitivity to CO2, overall, was equal in both states, State III occurred less often during hypoxia and hypercapnia, and hypoxic, urethane-anaesthetized rats sighed frequently, particularly in State I. This is also similar to the situation seen in unanesthetized rats. Given the similarities seen between urethane anesthetized rats in the present study and literature values for unanesthetized rats, the data suggest that urethane-anaesthetized rats provide a good model system for studying respiratory patterns and chemoreflexes as a function of cortical activation state.     

Oxidative stress and sleep apnoea in clinically healthy infants in the first year of life

Summary Question of the study   Respiratory instability as well as tissue damage by free radicals (oxidative stress) have been hypothesized to play a role in cases of sudden and unexpected infant death in the first year of life. The ratio of the oxidized/reduced form of redox compounds in the circulation could be used as a marker of oxidative stress. Therefore, the sleep apnoea rate and redox status of coenzyme Q10 (CoQ10) (percentage of the oxidized form in total CoQ10) were measured in a population of clinically healthy infants in their first year of life in order to study whether a physiological parameter of respiratory instability is related to a biochemical parameter of oxidative stress. Patients and methods   Between May and December 1999, 323 infants in the first year of life were referred to a paediatric sleep laboratory. Sleep apnoea rate, periodic breathing and parameters of oxygenation (SaO₂ and TcPO₂) were calculated based on polysomnographic recordings. The CoQ10 redox status was calculated based on high-pressure liquid chromatographic (HPLC) analysis. Results   Statistical analysis showed an age-dependent decrease in apnoea rate ( r = – 0.38) and CoQ10 redox status ( r = – 0.40). An increased CoQ10 redox status (median: 16.6 %; range: 7.3 – 29.7 %) was found in infants with high apnoea rates above the 90^th percentile of a reference group in comparison with infants with apnoea rates below the 90^th percentile of a reference group (median: 10.4 %; range: 5.1 – 20.4 %; P = 0.031). Conclusions   These findings may indicate that high apnoea rates are accompanied by increased formation of free radicals in clinically healthy infants in the first year of life.     

重点理工科高校大一新生焦虑状况及相关因素的研究

目的探讨重点理工科学校大一新生焦虑状况及相关因素,为进行针对性的干预提供依据。方法以广东某重点理工高校2007级的大一学生为研究对象,采用自行设计一般项目调查表、状态-特质焦虑量表（STAI）、匹兹堡睡眠质量指数量表（PSQI）、应付方式问卷进行测评。结果测查学生不论男女状态焦虑、特质焦虑分均显著高于地方常模;19.29%的学生睡眠质量较差;高状态焦虑组和高特质焦虑组解决问题、求助应付因子分均显著低于低状态焦虑组和低特质焦虑组,而自责、幻想、退避应付因子分则显著高于低状态焦虑组和低特质焦虑组;多元逐步回归分析说明,学生如常采用解决问题应付方式,在一定程度上可避免焦虑的产生,而睡眠质量差、采用自责应对方式则可加重焦虑水平。结论采取有效的认知应对策略其意义是使学生改变应激源,以使其变得威胁较小或变成挑战,把情绪基调训练成兴奋、期待和征服。     

The Reliability of Arousal Threshold During Sleep

Thirty-five subjects from two independent studies were awakened at EEG-defined periods during the night with 1000 Hz ascending tone series. Awakenings were made five to eight times per night during stage 2, stage 4, or REM sleep over a series of nights in good and poor sleepers. Reliability was assessed within stage, within night, between stages, and between nights. Good and poor sleepers did not differ in either depth of sleep or reliability of arousal threshold and were thus pooled in the analyses. From night to night, the most consistency was seen in stage 4 (r=.74), although REM reliability (r?₁= .49) and stage 2 reliability (r?₁= .50 and r?₁= .69 in the two respective studies) estimates were also greater than zero. Early sleep onset and morning arousals were more variable. Reliability estimates on arousal thresholds taken within the same night for stage 2 were r= .64 and r?₁= .77 for the two studies and r= .96 for REM. The depth of sleep was not correlated with awake auditory threshold. It was concluded that five or six carefully placed arousals could give a good estimate of an individual's usual arousal threshold.     

Longitudinal Study of Infant Sleep: Results of 14 Subjects Studied at Monthly Intervals

The sleep of 14 normal infants was studied every month throughout the first year. A computer program incorporated an analysis of multiple variables from polygraphic data as recommended by a recently standardized new born scoring manual. Under our recording conditions, quiet sleep increased during the first 3 months but indeterminate sleep did not decline over the year as expected. This finding is incompatible with the notion that indeterminate sleep reflects immaturity or “undifferentiation” in sleep organization.     

睡眠剥夺对HSP70表达及脑超微结构的影响

目的：观察睡眠剥夺（SD）后大鼠脑组织HSP70表达的变化及对超微结构的影响。方法：44只雄性SD大鼠随机分为11组，每组4只，免疫组织化学方法检测HSP70的表达，电镜观察海马超微结构的变化。结果：睡眠剥夺后12小时即可在大脑皮质及海马观察到HSP70阳性细胞，2—3天数量达到高峰，7天时明显下降。白天睡眠剥夺12小时（SDd12h）组HSP70阳性细胞数较夜晚睡眠剥夺12小时（SDn12h）组多（P〈0．05）。RS组大脑皮质HSP70阳性细胞数较白天睡眠剥夺1天（SDd1d）组减少（P〈0．05）。白天睡眠剥夺3天（SDd3d）海马出现超微结构改变，白天睡眠剥夺7天（SDd7d）后改变更加明显。结论：睡眠剥夺可影响大鼠脑组织HSP70表达及超微结构。