title: Differential sleep, sleepiness, and neurophysiology in the insomnia phenotypes of shift work disorder.
abstract: OBJECTIVE
  To characterize and compare insomnia symptoms within two common phenotypes of Shift Work Disorder.
  
  
  METHODS
  Observational laboratory and field study.
  
  
  METHODS
  Hospital sleep center.
  
  
  METHODS
  34 permanent night workers. Subjects were classified by Epworth Sleepiness Scale and Insomnia Severity Index into 3 subgroups: asymptomatic controls, alert insomniacs (AI), and sleepy insomniacs (SI).
  
  
  METHODS
  Sleep parameters were assessed by sleep diary. Circadian phase was evaluated by dim-light salivary melatonin onset (DLMO). Objective sleepiness was measured using the multiple sleep latency test (MSLT). Brain activity was measured using the N1 event-related potential (ERP). A tandem repeat in PER3 was genotyped from saliva DNA.
  
  
  RESULTS
  (1) AI group showed normal MSLT scores but elevated N1 amplitudes indicating cortical hyperarousal. (2) SI group showed pathologically low MSLT scores but normal N1 amplitudes. (3) AI and SI groups were not significantly different from one another in circadian phase, while controls were significantly phase-delayed relative to both SWD groups. (4) AI showed significantly longer sleep latencies and lower sleep efficiency than controls during both nocturnal and diurnal sleep. SI significantly differed from controls in nocturnal sleep parameters, but differences during diurnal sleep periods were smaller and not statistically significant. (5) Genotype × phenotype χ² analysis showed significant differences in the PER3 VNTR: 9 of 10 shift workers reporting sleepiness in a post hoc genetic substudy were found to carry the long tandem repeat on PER3, while 4 of 14 shift workers without excessive sleepiness carried the long allele.
  
  
  CONCLUSIONS
  Our results suggest that the sleepy insomnia phenotype is comprehensively explained by circadian misalignment, while the alert insomnia phenotype resembles an insomnia disorder precipitated by shift work.
authors.affiliation: Sleep Disorders and Research Center, Henry Ford Hospital, Detroit, MI: Magnetoencephalography Laboratory, Meadowlands Hospital, Secaucus, NJ.
authors.forename: Valentina
authors.initials: V
authors.lastname: Gumenyuk
authors.affiliation: Sleep Disorders and Research Center, Henry Ford Hospital, Detroit, MI: Pritzker School of Medicine, University of Chicago, Chicago, IL.
authors.forename: Ren
authors.initials: R
authors.lastname: Belcher
authors.affiliation: Sleep Disorders and Research Center, Henry Ford Hospital, Detroit, MI.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Drake
authors.affiliation: Sleep Disorders and Research Center, Henry Ford Hospital, Detroit, MI.
authors.forename: Thomas
authors.initials: T
authors.lastname: Roth
mesh_terms: D000483:Alleles; D001288:Attention / Q000502:physiology; D001921:Brain / Q000502:physiology; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology; D006970:Disorders of Excessive Somnolence / Q000150:complications / Q000235:genetics / Q000503:physiopathology; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000032:analysis / Q000096:biosynthesis / Q000528:radiation effects; D018598:Minisatellite Repeats / Q000235:genetics; D056950:Period Circadian Proteins / Q000235:genetics; D010641:Phenotype; D017286:Polysomnography; D012463:Saliva; D020178:Sleep Disorders, Circadian Rhythm / Q000150:complications* / Q000235:genetics / Q000503:physiopathology*; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications* / Q000235:genetics / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology*
chemical_list: C512644:PER3 protein, human; D056950:Period Circadian Proteins; D008550:Melatonin
keywords: Insomnia Severity Index (ISI); circadian phase; event-related brain potentials (ERPs); insomnia; multiple sleep latency test (MSLT); shift work