Differential sleep disturbances in two phenotypes of shift work disorder.
Roth-T; Belcher-R; Drake-CL; Mengel-HJ; Koshorek-GL; Gable-M; Gumenyuk-V
Sleep 2014 Mar; 37(Abstract Suppl):A163-A164
Introduction: Most patients meeting diagnostic criteria for Shift Work Disorder (SWD) report insomnia, but only a portion of these insomniacs also report excessive sleepiness. We hypothesize that two phenotypes of SWD, characterized by the presence or absence of excessive sleepiness, experience similar diurnal sleep but different nocturnal sleep. Methods: 35 night workers completed a sleep diary for two weeks before an overnight phase assessment. Subjects with a history of insomnia or other sleep disorders prior to shift work were excluded. At 17:00, each subject completed an Insomnia Severity Index specific to daytime sleep (ISI-D) and an Epworth Sleepiness Scale (ESS). 12 subjects with normal scores on both scales were classified as controls. 12 subjects with ESS < 10 and ISI-D > 10 were classified "alert insomniacs" (AI). 11 subjects with ISI-D > 10 and ESS > 10 were classified "sleepy insomniacs" (SI). We used t-tests to compare diary-reported sleep parameters between subgroups. Results: Dim-light melatonin onset was significantly (p < 0.01) delayed in controls (04:54 +/- 3.7 h) than in both SWD groups: AI (22:45 +/- 4.9 h) and SI (20:55 +/- 4.6 h). For daytime sleep, both SWD groups reported lower sleep efficiency (82.35% AI: 88.7 I % SI) and more awakenings (1.62 AI; 1.79 SI) than controls (95.78%; 0.54 awakenings, p < .05). The AI group also reported longer daytime latencies than controls (34.59 vs. 13.73 minutes, p < .05). At night, however, only the AI group differed from controls (p < .05), reporting lower sleep efficiency (81.84% vs. 93.38%), longer latencies (43.97 vs. 17.74 minutes) and more awakenings (1.90 vs. 0.80). Conclusion: Although both phenotypes of SWD show a nighttime phase and disrupted sleep during the day (a time outside of their circadian sleep phase), the AI phenotype shows sleep disturbances at night that are not seen in controls or the SI group. Since the AI phenotype presents both nocturnal and diurnal sleep disturbances, its etiology may be traced to factors outside circadian misalignment.
Sleep-deprivation; Sleep-disorders; Shift-work; Shift-workers; Work-intervals; Humans; Analytical-instruments; Analytical-models; Health-surveys; Physiological-fatigue; Physiological-response; Neurophysiological-effects; Neurophysiology; Work-performance; Brain-function
T. Roth, Sleep Disorders and Research Center, Henry Ford Hospital, Detroit, MI, USA
Henry Ford Health System, Detroit, Michigan