0680 ADULTS WITH DELAYED SLEEP-WAKE PHASE DISORDER HAVE MORE SLEEP AND CIRCADIAN VARIABILITY THAN HEALTHY CONTROLS

Abstract

Introduction: Delayed sleep-wake phase disorder (DSWPD) is characterized by sleep times that occur later than desired socially acceptable times. Assessment of the dim light melatonin onset (DLMO) in DSWPD is encouraged to improve diagnostic accuracy, and to optimize timing of light and/or melatonin treatment. However, the DLMO is often implicitly assumed to be stable in DSWPD. Here we compared sleep and circadian variability in DSWPDs versus healthy controls under the same conditions. Methods: Twenty-two DSWPDs and 18 controls (21-52 years) completed a 10-day protocol consisting of two DLMO assessments, a 5-day study break, and then two more DLMO assessments. All participants were instructed to sleep within 1 hour of their self-reported average sleep schedule during the study break. Sleep onset, wake time, sleep efficiency (after sleep onset), and total sleep time were extracted from wrist actigraphy recordings. Results: There were no group differences in sex, age, race, or employment status between the DSWPDs and controls. As expected, the DSWPDs had significantly later sleep onsets, later wake times, and later DLMOs than controls (all p<0.001). Root mean squared successive difference calculations revealed that the DSWPDs had significantly more night-to-night variability in their wake time and total sleep time than controls (p≤0.015), but similar night-to-night variability in sleep onset time and sleep efficiency (p≥0.30). DSWPDs had more drift in their DLMOs from before to after study break than controls (p=0.05). Conclusion: Under the same conditions, we found increased sleep and circadian variability in DSWPDs versus controls. The increased sleep variability in DSWPD could be clinically significant, as sleep variability is associated with worse health outcomes, including depression, insomnia, obesity and insulin resistance. Furthermore, DSWPD patients with higher sleep variability are more likely to have a shifting, rather than stable DLMO, which should be taken into consideration when timing light and/or melatonin treatment.