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.

中文翻译：

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昼夜节律和与年龄有关的热感受和温度调节调制：机制和功能含义。

在老年人中，体温的昼夜节律显示振幅降低，相位提前和稳定性降低。本综述评估了这些变化可能在多大程度上由温度调节系统的几个水平上与年龄相关的缺陷所引起，这些温度调节包括热感受，生热和保存，热量损失和中央调节。尽管某些变化本身与衰老过程有关，但其他变化似乎是其他因素的继发因素，随着年龄的增长，风险增加，尤其是健身和体育锻炼的水平下降。此外，讨论了体温节律的功能含义。例如，几乎没有研究昼夜节律与体温调节之间的关系，而证据表明睡眠质量取决于这两个方面。有人提出不应将等温线温度的昼夜节律视为早期进化过程中的等温线残余，而应从分子水平到认知对生理学具有重要的功能意义。提出了关于昼夜节律在外周血管舒张中的功能意义以及随之而来的皮肤和核心温度反相节律的新观点。由于同时采取了行为措施以防止热量散失，因此每天发生的强烈的，外围的血管舒张反应主要不可能是由于设定点降低而引起的热量散失。有几种迹象表明，它们在免疫宿主防御机制中起支持作用。鉴于温度节律的功能重要性，