Patients with delayed sleep-wake phase disorder (DSWPD) tend to sleep later than healthy controls, though there are no differences between the groups in terms of sleep duration, the degree of social jetlag, and intraindividual standard deviation in sleep timing, according to study results published in Frontiers in Psychology.
Epidemiological studies indicate that DSWPD may be associated with poor academic performance, poor attendance at school, poor health behaviors, and mental health issues. However, few studies have investigated day-to-day sleep variations in youth with DSWPD. The objective of this study was to explore habitual sleep, social jetlag, and day-to-day variations in sleep among youth with DSWPD compared with healthy controls and to evaluate evening and morning performance in both groups.
In this study, researchers examined 40 patients with DSWPD and 21 healthy controls aged between 16 and 25 years. Objective and subjective sleep were measured over 7 days on a habitual sleep schedule using a sleep journal and actigraphy recordings. Items in the sleep journal included bedtime and rising time, number and duration of awakenings, and sleep quality and daytime functioning on scales from 1 to 5. Reaction time was tested 2 times with a 12-hour interval (22:00 and 10:00 the next morning) using a simple 10-minute sustained reaction time test administered on a handheld computer.
Results revealed that the DSWPD group had later habitual sleep timing compared with healthy controls (01:59±113 vs 23:54±40 on weekdays, respectively, and 03:10±124 vs 01:05±87 on weekends, respectively; P <.001), though sleep duration, social jetlag, and intraindividual standard deviation in sleep timing did not differ between groups. Patients with DSWPD also reported longer sleep onset latency and poorer sleep efficiency, sleep quality, and daytime function than healthy controls on weekdays and weekends. Evening performances on the reaction time test were similar between both the DSWPD and healthy control groups, though the DSWPD group experienced a higher number of lapses in the morning compared with healthy controls (5.4±6.9 vs 1.0±1.3, respectively; P <.001).
This study had several limitations. First, findings may not be generalized to other populations with DSWPD. Second, researchers did not have in-depth information about the physical and social environments of all patients, which may have affected social jetlag results. Third, the reaction time test protocol used in this study may have interfered with the accuracy of results. Fourth, the sample size in this study was relatively small and may have led to some analyses being underpowered.
The study researchers concluded that youth with DSWPD have later timing of sleep compared with healthy controls, and that poor morning performance in DSWPD may illustrate the challenges this population faces when trying to fulfill early morning obligations.
Saxvig IW, Wilhelmsen-Langeland A, Pallesen S, Nordhus IH, Vedaa Ø, Bjorvatn B. Habitual sleep, social jetlag, and reaction time in youths with delayed sleep-wake phase disorder. A case-control study [published online November 12, 2019]. Front Psychol. doi: 10.3389/fpsyg.2019.02569