Evaluating sleepiness using force platform posturography requires less than 30 seconds of measurement time

We have investigated the relationship between measurement time and accuracy of posturography-based sleep deprivation estimation. Twenty healthy subjects, 20 to 37 years of age, participated in the study. The subjects were deprived of sleep for up to 36 hours. The postural stability of the subjects was measured as a function of sleep deprivation time. The posturographic parameters used for analysing the test data were the fractal dimension of the sway path, the most common frequency of the sway, the time-interval for open-loop control of the stance and the most common amplitude of the sway. Individual case-observations showed that we were able to estimate the sleep deprivation time of individual subjects with an accuracy better than +/-3 hours, when the measurement time was the commonly utilized 30 seconds. Repeating the analysis with shorter measurement times we found that a measurement length of 26, 23, and 20 seconds for the fractal dimension, most common frequency of sway and most common sway amplitude respectively, was required in order to achieve a 20% relative sleep deprivation estimation accuracy. The sleep deprivation estimation accuracy based on the time-interval for open-loop control of stance remained at 6% when the measurement time was shortened to 20 seconds.