Separated insomnia severity index (ISI) distinguishes two phenotypes of shift work disorder.
Belcher-R; Roth-T; Drake-CL; Mengel-HJ; Bazan-L; Gumenyuk-V
Sleep 2014 Mar; 37(Abstract Suppl):A204
Introduction: Most patients meeting diagnostic criteria tor SWD report insomnia. At the same time, 20-25% of the general population has insomnia. We hypothesize that a subgroup of SWD patients experience sleep difficulties primarily related to circadian misalignment, while another subgroup has an insomnia disorder per se precipitated by shift work. Methods: 35 night workers participated in an overnight phase and MSLT assessment. Subjects with a history of insomnia or other sleep disorders prior to shift work were excluded. At 17:00, each subject completed an Epworth Sleepiness Scale (ESS) and two ISI scales: one specific to nighttime/off-shift sleep (ISI-N) and the other specific to day time/on-shift sleep (ISI-D). Questions were identical to the standardized ISI, but instructions referred specifically to either daytime or nighttime sleep. 12 subjects with normal scores on all 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). Results: AI showed elevated ISI scores with no significant difference between ISI-D (14.67 +/- 3.17) and ISI-N (11.42 +/- 6.93, p > .10), indicating sleep disturbances even during nighttime sleep. In contrast, SI had significantly lower ISI-N scores (9.18 +/- 6.73) than ISI-D scores (14.27 +/- 4.8 1, p < .001), indicating they sleep better at night. Nocturnal five-nap MSLT scores (22:30-06:30) were not significantly different between AI (7.8 +/- 5.1) and controls (8.1 +/- 3.4), but scores among the SI group were significantly lower (3.1 +/- 3.0, p < .01). Conclusion: Use of a separated day/night ISI distinguishes between two insomnia phenotypes of SWD and may assist in the clinical management of the disorder. The insomnia/excessive sleepiness phenotype is associated with normal sleep during the night and pathological sleepiness, while the insomnia-only phenotype shows no difference in sleep disturbances between nocturnal and diurnal sleep. Patients with elevated scores on both scales may benefit from insomnia treatment in addition to phase alignment.
Sleep-deprivation; Sleep-disorders; Shift-work; Shift-workers; Work-intervals; Circadian-rhythms; Humans; Physiology; Physiopathology; Analytical-instruments; Analytical-models; Health-surveys; Questionnaires; Physiological-fatigue; Physiological-response
R. Belcher, Sleep Disorders and Research Center, Henry Ford Hospital, Detroit, MI, USA
Henry Ford Health System, Detroit, Michigan