Daytime changes in postural stability and repeatability of posturographic measurements.
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.
Forsman
Pia
P
Finnish Institute of Occupational Health, Helsinki, Finland. Pia.Forsman@ttl.fi
Haeggström
Edward
E
Wallin
Anders
A
Toppila
Esko
E
Pyykkö
Ilmari
I
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