[Multivariate statistical analysis in stabilometry in human upright standing (the first report)--age-related factor].

Posturography is not a clearly defined examination. Recently a number of parameters can be obtained in stabilometry by means of computers. To evaluate each parameter and to decide its normal range, subject's age must be considered. The age-related factors found in stabilometry were studied in terms of both multiple regression analysis and cluster analysis. The parameters used in this study were as follows: the area of an ellipse for rejection and of the figure displayed on an X-Y recorder, the maximum width on both the X axis (left and right direction) and the Y axis (anterior and posterior direction), the total length and the sum of excursion in each direction, the root mean square, the velocity, the acceleration, and the averaged frequency of body sway in both X and Y directions. One hundred normal subjects, aged from the second to sixth decade, including 10 males and 10 females in each decade, were tested. Each subject was asked to stand on a platform in Romberg's position for 60 seconds with both eyes open and closed. The significant parameters to predict age, which were determined by multiple regression analysis, were as follows (P less than 0.05): the averaged frequency in the Y direction with eyes closed, the maximum width in the X direction with eyes open, the area of the ellipse for rejection and of the figure with eyes closed, the maximum width in the Y direction and the area of the ellipse and the velocity in the X direction with eyes open. All test subjects were successfully classified into two groups by cluster analysis. One was the younger group aged less than 40 years and the other was the older group not younger than 40-year-old. However, the difference between with eyes open and with eyes closed was not significant (P less than 0.01) as regards the parameters of root mean square and averaged frequency in both sexes and at every decade. The difference between both sexes was supposed to be significant in the Y direction in the younger group and in the X direction in the older one.