Abstract
Behavioral and physiological processes exhibit circadian rhythms in most organisms including humans. These rhythms are driven by a system of self-sustained clocks and are entrained by external cues. The mammalian central oscillator, suprachiasmatic nucleus (SCN) incorporates environmental information and orchestrates slave oscillators in peripheral cells. The circadian clock system is composed of a hierarchy of oscillators that involve transcription and translation feedback loops of multiple clock genes. Advanced sleep phase type, delayed sleep phase type and non-entrained type of circadian rhythm sleep disorders (CRSD) are thought to at least partly result from malfunction/maladaptation of the circadian system. Dissection of human circadian clock system is indispensable to understand the pathophysiology of CRSD. However, it is laborious and costly to assess individual’s circadian rhythms precisely, since the subject is usually required to stay in a laboratory environment free from external cues and masking effects for over a couple of weeks. Therefore, more convenient measurements of circadian properties are demanded to reduce patients’ burden. In this review, we discuss the pathophysiology of CRSD and surrogate measurements for assessing individual’s circadian properties.
