Social jetlag has recently attracted attention as the circadian misalignment between biological and social clocks. We aimed to examine social jetlag and its effect on daytime sleepiness and daily functions in patients with narcolepsy, behaviorally induced insufficient sleep syndrome (BIISS) and delayed sleep-wake phase disorder (DSPD). The levels of social jetlag (SJLmid) and sleep-corrected social jetlag (SJLsc) were calculated for each patient, and the effect of these social jetlag-related parameters on daytime sleepiness and daily functions were examined. Objective sleepiness measured by the mean sleep latency in the multiple sleep latency test, subjective sleepiness assessed by the Epworth sleepiness scale (ESS), health-related quality of life (HRQoL) assessed by the SF-8 health survey, and incidences of mistakes in daily activities, traffic accidents and near-miss events related to daytime sleepiness were compared among the narcolepsy (n = 39), BIISS (n = 87) and DSPD (n = 28) groups. Both SJLmid and SJLsc showed a negative correlation with physical HRQoL in patients with narcolepsy and a positive correlation with the ESS score in patients with DSPD. In patients with BIISS, SJLsc reflected sleep loss rather than circadian misalignment; moreover, SJLsc was not associated with daytime sleepiness and daily functions. Social jetlag was not associated with incidences of mistakes in daily activities, traffic accidents and near-miss events. The state of social jetlag and its association with daily functions differed among the narcolepsy, BIISS and DSPD groups. Social jetlag represented sleep debt in BIISS, circadian misalignment in narcolepsy and both in DSPD. Our results thus show that the clinical manifestations and significance of social jetlag differ depending on the underlying sleep disorders.
Keywords: Social jetlag; behaviorally induced insufficient sleep syndrome; daily functions; daytime sleepiness; delayed sleep-wake phase disorder; health-related quality of life; narcolepsy.