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Daytime Changes in Postural Stability and Repeatability of Posturographic Measurements

Forsman, Pia Lic Phil; Haeggström, Edward PhD, Doc; Wallin, Anders MSc; Toppila, Esko PhD, Doc; Pyykkö, Ilmari MD, PhD

Journal of Occupational and Environmental Medicine: June 2007 - Volume 49 - Issue 6 - p 591-596
doi: 10.1097/JOM.0b013e3180577796
Original Articles

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.

From the Finnish Institute of Occupational Health (Ms Forsman, Dr Toppila), Helsinki, Finland; Electronics Research Unit (Dr Haeggström, Mr Wallin), Department of Physical Sciences, University of Helsinki, Helsinki, Finland; Helsinki Institute of Physics (Dr Haeggström), Helsinki, Finland, and the Department of Otolaryngology (Dr Pyykkö), University of Tampere, Tampere, Finland.

CME Available for this Article at

Pia Forsman has no commercial interest related to this research.

Address correspondence to: Pia Forsman, Lic Phil, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, FI-00250 Helsinki, Finland; E-mail:

©2007The American College of Occupational and Environmental Medicine