title: Daytime changes in postural stability and repeatability of posturographic measurements.
abstract: OBJECTIVE
  Daytime sleepiness correlates with sleep-related accidents, but convenient tests for occupational sleepiness monitoring are scarce. The effect of daytime on balance, on posturographic measurements, and on their repeatability was investigated in 30 healthy volunteers as part of our work to develop such a test.
  
  
  METHODS
  The daytime effect was assessed by measuring balance at 8:30 am, 10:30 am, and 1:30 pm. The repeatability was assessed with morning trials once a week for 1 month. The posturographic test was performed on a static force platform, and the balance was evaluated from a fractal dimension of sway, most common sway amplitude, and time interval for open-loop stance control.
  
  
  RESULTS
  The balance worsened during the day, and it was possible to determine whether the measurement was performed in the morning or in the afternoon. The morning balance remained unchanged during the month-long test.
  
  
  CONCLUSIONS
  Posturographic measurements are repeatable and have a circadian effect, which may be influenced by sleepiness.
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland. Pia.Forsman@ttl.fi
authors.forename: Pia
authors.initials: P
authors.lastname: Forsman
authors.forename: Edward
authors.initials: E
authors.lastname: Haeggström
authors.forename: Anders
authors.initials: A
authors.lastname: Wallin
authors.forename: Esko
authors.initials: E
authors.lastname: Toppila
authors.forename: Ilmari
authors.initials: I
authors.lastname: Pyykkö
mesh_terms: D000062:Accidents, Occupational; D000328:Adult; D000704:Analysis of Variance; D002940:Circadian Rhythm / Q000502:physiology*; D005221:Fatigue / Q000150:complications*; D005260:Female; D006801:Humans; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D015203:Reproducibility of Results; D013997:Time Factors