Sleep and circadian variability in people with delayed sleep–wake phase disorder versus healthy controls

Abstract

Objective/Background To compare sleep and circadian variability in adults with delayed sleep-wake phase disorder (DSWPD) to healthy controls. Patients/Methods Forty participants (22 DSWPD, 18 healthy controls) completed a 10-day protocol, consisting of DLMO assessments on two consecutive nights, a five-day study break, followed by two more DLMO assessments. All participants were instructed to sleep within one hour of their self-reported average sleep schedule for the last four days of the study break. We analyzed the participants’ wrist actigraphy data during these four days to examine intraindividual variability in sleep timing, duration and efficiency. We also examined shifts in the DLMO from before and after the study break. Results and Conclusions Under the same conditions, people with DSWPD had significantly more variable wake times and total sleep time than healthy controls (p≤0.015). Intraindividual variability in sleep onset time and sleep efficiency was similar between the two groups (p≥0.30). The DLMO was relatively stable across the study break, with only 11% of controls but 27% of DSWPDs showed more than a one hour shift in the DLMO. Only in the DSWPD sample was greater sleep variability associated with a larger shift in the DLMO (r=0.46, p=0.03). These results suggest that intraindividual variability in sleep can be higher in DSWPD versus healthy controls, and this may impact variability in the DLMO. DSWPD patients with higher intraindividual variability in sleep are more likely to have a shifting DLMO, which could impact sleep symptoms and the optimal timing of light and/or melatonin treatment for DSWPD.

<p>Impact of Mandatory Wake Time on Sleep Timing, Sleep Quality and Rest-Activity Cycle in College and University Students Complaining of a Delayed Sleep Schedule: An Actigraphy Study</p>

“…Some studies reported shorter sleep duration in delayed individuals compared to controls, 3,[6][7][8] but others did not find any difference. [9][10][11][12] The same is true for sleep quality measured with actigraphy: some studies found decreased sleep efficiency in delayed individuals, 13 whereas others reported normal sleep parameters compared to controls. [9][10][11][12]14 Delayed individuals are expected to have normal sleep duration and quality when they can sleep at their spontaneous sleep time.…”

“…[9][10][11][12] The same is true for sleep quality measured with actigraphy: some studies found decreased sleep efficiency in delayed individuals, 13 whereas others reported normal sleep parameters compared to controls. [9][10][11][12]14 Delayed individuals are expected to have normal sleep duration and quality when they can sleep at their spontaneous sleep time. 2 Therefore, discrepancies in previous studies might be explained by a poor differentiation between nights with or without obligations in the morning.…”

“…Using a sleep questionnaire, a study found that a later chronotype was associated with lower subjective sleep quality on work days compared to days off. 17 Using actigraphy, one study on DSWPD patients failed to observe a difference in sleep efficiency or total sleep time between weekdays and weekends, 11 whereas another study on E-types found decreased sleep efficiency on weekdays. 8 Comparing weekdays and weekends, however, does not account for morning obligations during the weekend or for obligation-free mornings during the week.…”

“…In fact, in studies on DSWPD patients, many participants were unemployed and their wake times on weekdays were too late for standard starting work or school times. 11,14,18 Usually, E-types do attempt to follow the schedule imposed by work or school but some of them find it difficult: they often arrive late and they occasionally miss their first class. As a result, these delayed individuals present the main clinical feature of DSWPD which is a complaint that eveningness is a source of problems in their everyday life.…”

“…20 Greater social jetlag may increase the overall variability in sleep parameters. Indeed, variability in sleep timing and duration is greater in DSWPD patients than in healthy controls, 11 and more variability is associated with later circadian phase. 21 Moreover, increased activity during the night due to more time awake, and decreased activity during the day due to daytime sleepiness may also decrease the amplitude of the rest-activity cycle on work days compared to free days.…”