title: Wrist actigraphic measures of sleep in space.
abstract: OBJECTIVE
  To determine whether wrist actigraphy is useful as a tool for space-based sleep research. Specifically, to determine whether bedtimes and waketimes can be identified from the actigraphic record, and whether actigraphic measures of sleep in space are related to polysomnographic (PSG) ones.
  
  
  METHODS
  Actigraphy, sleep diary, and Polysomnographic (PSG) measures of sleep were obtained from four subjects in two 72h measurement blocks occurring 2d and 12d into a 17d Space Shuttle mission in orbiting the earth in microgravity.
  
  
  METHODS
  Four healthy male astronauts aged 38y - 47y.
  
  
  METHODS
  NA.
  
  
  RESULTS
  Sleep onset and offset at "night" could be quite clearly identified from the actigraphic record and were better estimated by actigraph than by diary. There was a high correlation between actigraphic and PSG estimates of sleep duration (r = 0.96) and sleep efficiency (r = 0.88), and a similarity in the mean estimates obtained. On a minute-by-minute basis, there was a good correlation between sleep stage and actigraphic movement counts, with a higher level of counts per minute recorded in epochs with lighter PSG sleep stages. There was also a high correlation (r = 0.90) between minutes of stage 0 (wake) occurring between bedtime and wake time, and number of non-zero actigraph epochs during the same interval.
  
  
  CONCLUSIONS
  Actigraphy worked well in space both as a way of detecting bedtimes and waketimes, and as an indicant of sleep restlessness.
authors.affiliation: Sleep and Chronobiology Center, University of Pittsburgh Medical Center, Western Psychiatric Institute and Clinic, PA 15213, USA. monkth@msx.upmc.edu
authors.forename: T H
authors.initials: TH
authors.lastname: Monk
authors.forename: D J
authors.initials: DJ
authors.lastname: Buysse
authors.forename: L R
authors.initials: LR
authors.lastname: Rose
mesh_terms: D000328:Adult; D000337:Aerospace Medicine; D004594:Electrophysiology / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012146:Rest / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D013026:Space Flight; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology; D014953:Wrist / Q000502:physiology*