title: EEG spectral analysis in primary insomnia: NREM period effects and sex differences.
abstract: OBJECTIVE
  To compare NREM EEG power in primary insomnia (PI) and good sleeper controls (GSC), examining both sex and NREM period effects; to examine relationships between EEG power, clinical characteristics, and self-reports of sleep.
  
  
  METHODS
  Overnight polysomnographic study.
  
  
  METHODS
  Sleep laboratory.
  
  
  METHODS
  PI (n=48; 29 women) and GSC (n=25; 15 women).
  
  
  METHODS
  None.
  
  
  METHODS
  EEG power from 1-50 Hz was computed for artifact-free sleep epochs across four NREM periods. Repeated measures mixed effect models contrasted differences between groups, EEG frequency bands, and NREM periods. EEG power-frequency curves were modeled using regressions with fixed knot splines.
  
  
  RESULTS
  Mixed models showed no significant group (PI vs. GSC) differences; marginal sex differences (delta and theta bands); significant differences across NREM periods; and group*sex and group*NREM period interactions, particularly in beta and gamma bands. Modeled power-frequency curves showed no group difference in whole-night NREM, but PI had higher power than GSC from 18-40 Hz in the first NREM period. Among women, PI had higher 16 to 44-Hz power than GSC in the first 3 NREM periods, and higher 3 to 5-Hz power across all NREM periods. PI and GSC men showed no consistent differences in EEG power. High-frequency EEG power was not related to clinical or subjective sleep ratings in PI.
  
  
  CONCLUSIONS
  Women with PI, but not men, showed increased high-frequency and low-frequency EEG activity during NREM sleep compared to GSC, particularly in early NREM periods. Sex and NREM period may moderate quantitative EEG differences between PI and GSC.
authors.affiliation: Neuroscience Clinical and Translational Research Center and Sleep Medicine Institute, University ofPittsburgh School ofMedicine, Pittsburgh, PA, USA. buyssedj@upmc.edu
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Buysse
authors.forename: Anne
authors.initials: A
authors.lastname: Germain
authors.forename: Martica L
authors.initials: ML
authors.lastname: Hall
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Moul
authors.forename: Eric A
authors.initials: EA
authors.lastname: Nofzinger
authors.forename: Amy
authors.initials: A
authors.lastname: Begley
authors.forename: Cindy L
authors.initials: CL
authors.lastname: Ehlers
authors.forename: Wesley
authors.initials: W
authors.lastname: Thompson
authors.forename: David J
authors.initials: DJ
authors.lastname: Kupfer
mesh_terms: D000328:Adult; D000339:Affect / Q000502:physiology; D001143:Arousal / Q000502:physiology; D002540:Cerebral Cortex / Q000503:physiopathology; D004569:Electroencephalography; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012016:Reference Values; D012737:Sex Factors; D012815:Signal Processing, Computer-Assisted; D007319:Sleep Initiation and Maintenance Disorders / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology; D055815:Young Adult