The endogenous circadian temperature period length (tau) in delayed sleep phase disorder compared to good sleepers

Aug 1, 2013Journal of sleep research

Body clock cycle length in people with delayed sleep phase compared to good sleepers

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Abstract

The core temperature rhythm of participants with delayed sleep phase disorder (DSPD) averaged 24 hours 54 minutes, significantly longer than the 24 hours 29 minutes of good sleepers.

Participants with DSPD exhibited a longer core temperature rhythm period than those without the disorder.
The rapid delay in temperature rhythm for DSPD participants was greater than 25 minutes per day.
These findings may explain the challenges DSPD patients face in adjusting to earlier sleep times.
Frequent relapses following treatment could be linked to the longer circadian rhythm period observed in DSPD patients.

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The currently assumed aetiology for delayed sleep phase disorder (DSPD) is a delay of the circadian system. Clinicians have sought to use bright light therapy, exogenous melatonin or chronotherapy to correct the disorder. However, these treatments have achieved unreliable outcomes for DSPD patients and, as such, one suggestion has been that the disorder may be caused by a longer than normal circadian rhythm period length (i.e. tau). The present study investigated this premise using a 78-h ultradian, ultra-short sleep-wake cycle. This constant bedrest routine was used to simulate a series of 1-h long 'days' by alternating 20-min sleep opportunities and 40 min of enforced wakefulness. Thirteen participants were recruited for the study including, six people diagnosed with DSPD according to the International Classification of Sleep Disorders-2 [mean age = 22.0, standard deviation (SD) = 3.3] and seven good sleepers (mean age = 23.1, SD = 3.9) with normal sleep timing. The DSPD participants' core temperature rhythm tau (mean = 24 h 54 min, SD = 23 min) was significantly longer (t = -2.33, P = 0.04, Cohen's d = 1.91) than the good sleepers' (mean 24 h 29 min, SD = 16 min). The temperature rhythm of the DSPD participants delayed more rapidly (i.e. >25 min day(-1) ) than the good sleepers'. These findings provide an explanation for the difficulty that DSPD patients have in phase advancing to a more conventional sleep time and their frequent relapse following treatment. The outcomes of this study support a vigorous and continued application of chronobiological and behavioural therapies to entrain DSPD patients to their desired earlier sleep times.

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The endogenous circadian temperature period length (tau) in delayed sleep phase disorder compared to good sleepers

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