Continuous measurement of temperature in non‐24 hour sleep‐wake syndrome

Abstract The onset of the low temperature (LT) zone which was defined as a period when the rectal temperature was below its daily mean is a convenient circadian phase marker. In this study, we document three cases of non‐24 h sleep‐wake syndrome in which identification of the LT zone as an evening circadian phase marker contributed to clinical judgments. We found that the LT zone was correlated well with dim light melatonin onset. Moreover, calculating the LT zone was useful in determining phase position in irregular sleep pattern and in determining the timing of bright light therapy.