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Circadian rhythms of early morning awakening insomniacs
Author(s) -
LACK LEON C.,
MERCER JEREMY D.,
WRIGHT HELEN
Publication year - 1996
Publication title -
journal of sleep research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 117
eISSN - 1365-2869
pISSN - 0962-1105
DOI - 10.1111/j.1365-2869.1996.00211.x
Subject(s) - circadian rhythm , morning , psychology , insomnia , rhythm , melatonin , delayed sleep phase , arousal , chronobiology , audiology , medicine , sleep disorder , neuroscience , psychiatry
SUMMARY It has been suggested that two types of insomnia, sleep onset insomnia and early morning awakening insomnia, may be caused by delays and advances respectively of circadian rhythms. Evidence supports the circadian rhythm phase delay of sleep onset insomniacs. The present study investigated the phase timing of circadian rhythms of early morning awakening insomniacs compared with a group of age matched good sleepers. A 24‐h bed rest laboratory session was used to evaluate the endogenous core body temperature and urinary melatonin rhythms. Objective and subjective sleepiness were also measured every 30 min across the session with 10 min multiple sleep latency tests and Stanford Sleepiness Scale. Maximum and minimum phases of each individual's rhythm were identified using two‐component cosine curve fitting. Compared with the good sleepers, the insomniacs had significant phase advances of 2 4 h for the temperature and melatonin rhythms. However, the 0‐4 h advances of the sleepiness rhythms were not significant. This latter unexpected result was explained on the basis of variability of sleepiness measures. It was suggested that early morning awakening insomnia arises from phase advanced circadian rhythms which evoke early arousal's from sleep.