title: The sleep EEG as a marker of intellectual ability in school age children.
abstract: OBJECTIVE
  To investigate the within-subject stability in the sleep EEG and the association between the sleep EEG and intellectual abilities in 9- to 12-year-old children.
  
  
  METHODS
  Intellectual ability (WISC-IV, full scale, fluid, and verbal IQ, working memory, speed of processing) were examined and all-night polysomnography was performed (2 nights per subject).
  
  
  METHODS
  Sleep laboratory.
  
  
  METHODS
  Fourteen healthy children (mean age 10.5 ± 1.0 years; 6 girls).
  
  
  RESULTS
  Spectral analysis was performed on artifact-free NREM sleep epochs (C3/A2). To determine intra-individual stability and inter-individual variability of the sleep EEG, power spectra were used as feature vectors for the estimation of Euclidean distances, and intraclass correlation coefficients (ICC) were calculated for the 2 nights. Sleep spindle peaks were identified for each individual and individual sigma band power was determined. Trait-like aspects of the sleep EEG were observed for sleep stage variables and spectral power. Within-subject distances were smaller than between-subject distances and ICC values ranged from 0.72 to 0.96. Correlations between spectral power in individual frequency bins and intelligence scores revealed clusters of positive associations in the alpha, sigma, and beta range for full scale IQ, fluid IQ, and working memory. Similar to adults, sigma power correlated with full scale (r = 0.67) and fluid IQ (r = 0.65), but not with verbal IQ. Spindle peak frequency was negatively related to full scale IQ (r = -0.56).
  
  
  CONCLUSIONS
  The sleep EEG during childhood shows high within-subject stability and may be a marker for intellectual ability.
authors.affiliation: Child Development Center, University Children’s Hospital Zurich, Zurich, Switzerland.
authors.forename: Anja
authors.initials: A
authors.lastname: Geiger
authors.forename: Reto
authors.initials: R
authors.lastname: Huber
authors.forename: Salomé
authors.initials: S
authors.lastname: Kurth
authors.forename: Maya
authors.initials: M
authors.lastname: Ringli
authors.forename: Oskar G
authors.initials: OG
authors.lastname: Jenni
authors.forename: Peter
authors.initials: P
authors.lastname: Achermann
mesh_terms: D000367:Age Factors; D000375:Aging; D002648:Child; D003071:Cognition / Q000502:physiology; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D007361:Intelligence Tests / Q000706:statistics & numerical data; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D017286:Polysomnography / Q000379:methods; D012016:Reference Values; D015203:Reproducibility of Results; D012890:Sleep / Q000502:physiology*