title: Higher plasma IGF-1 levels are associated with increased delta sleep in healthy older men.
abstract: BACKGROUND
  Sleep quality declines with age, with less time in deep or slow wave sleep (SWS) and reduced amplitude of the delta waves that characterize it. Age-related declines also occur in lean body mass, growth hormone (GH), and insulin-like growth factor 1 (IGF-1). These changes in sleep quality and anabolic status may be related, as administration of GH or growth hormone releasing hormone (GHRH) can enhance SWS and decrease awakenings in young men. Here we examine the relationship between plasma IGF levels and delta sleep quality in older men.
  
  
  METHODS
  The sleep EEG of 30 healthy elderly men (64 +/- 6 yrs; range 50-75) was recorded on the second of 2 consecutive nights. Plasma samples were drawn within 3 weeks of EEG recording, and IGF levels were assayed by RIA after acid extraction.
  
  
  RESULTS
  IGF explained 28% (semi-partial correlation coefficient r = .53; p = .003) of the variance in average delta energy per epoch of SWS, after age-related variance was removed. Higher IGF was associated with higher average delta energy. Similar results were obtained for total delta energy during SWS (r = .37, p = .04) 4nd time spent in SWS (r = .42, p = .02). Other measures of sleep quality (e.g., wakefulness, REM sleep) were not correlated with IGF. The IGF delta relationship was minimally influenced by moderator variables such as thyroxine (T3, T4), and/or body mass index (BMI).
  
  
  CONCLUSIONS
  We conclude that age-adjusted IGF levels in healthy senior men co-vary significantly with SWS and the delta energy that characterizes it.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, USA.
authors.forename: P N
authors.initials: PN
authors.lastname: Prinz
authors.forename: K E
authors.initials: KE
authors.lastname: Moe
authors.forename: E M
authors.initials: EM
authors.lastname: Dulberg
authors.forename: L H
authors.initials: LH
authors.lastname: Larsen
authors.forename: M V
authors.initials: MV
authors.lastname: Vitiello
authors.forename: B
authors.initials: B
authors.lastname: Toivola
authors.forename: G R
authors.initials: GR
authors.lastname: Merriam
mesh_terms: D000368:Aged; D003700:Delta Rhythm; D004569:Electroencephalography; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D012890:Sleep / Q000502:physiology*
chemical_list: D007334:Insulin-Like Growth Factor I