Introduction: The efficacy of bright light and/or melatonin treatment for Delayed Sleep Wake Phase Disorder (DSWPD) is contingent upon an accurate clinical assessment of the circadian phase. However, the process of determining this circadian phase can be costly and is not yet readily available in the clinical setting. The present study investigated whether more cost-effective and convenient estimates of the circadian phase, such as self-reported sleep timing, can be used to predict the circadian phase and guide the timing of light and/or melatonin treatment (i.e. dim-light melatonin onset, core body temperature minimum and melatonin secretion mid-point) in a sample of individuals with DSWPD.
Method: Twenty-four individuals (male = 17; mean age = 21.96, SD = 5.11) with DSWPD were selected on the basis of ICSD-3 criteria from a community-based sample. The first 24-hours of a longer 80-hour constant laboratory ultradian routine were used to determine core body temperature minimum (cBTmin), dim-light melatonin onset (DLMO) and the midpoint of the melatonin secretion period (DLMmid = [DLM°ff-DLMO]/2). Prior to the laboratory session subjective sleep timing was assessed using a 7-day sleep/wake diary, the Pittsburgh Sleep Quality Index (PSQI), and the Delayed Sleep Phase Disorder Sleep Timing Questionnaire (DSPD-STQ).
Results: Significant moderate to strong positive correlations were observed between self-reported sleep timing variables and DLMO, cBTmin and DLMmid. Regression equations revealed that the circadian phase (DLMO, cBTmin and DLMmid) was estimated within ±1.5 hours of the measured circadian phase most accurately by the combination of sleep timing measures (88% of the sample) followed by sleep diary reported midsleep (83% of the sample) and sleep onset time (79% of the sample).
Discussion: These findings suggest that self-reported sleep timing may be useful clinically to predict a therapeutically relevant circadian phase in DSWPD.
Keywords: Chronobiologic treatment; Circadian phase; Delayed Sleep Wake Phase Disorder; self-reported sleep timing.