Background: Reliable normative data for force platform measurements of postural balance have not been available.
Methods: Data on postural balance were collected from a representative nationwide sample of a Finnish population aged >or=30 years (n = 7,979). As part of a comprehensive health survey (Health 2000), postural balance was measured with the help of a force platform system in four test conditions: normal standing with eyes open and closed (both for 30 s), semi-tandem (20 s) and tandem stand with eyes open (20 s). In addition, balance abilities were also evaluated by a non-instrumented field test.
Results: The main findings of this study indicated that the differences in balance between subjects belonging to different age categories were apparent already among young and middle-aged subjects. This is true, however, only for the more accurate force platform measurements, as the field test showed a clear ceiling effect up to 60 years of age. At higher ages both methods indicated a further, accelerating decline in balance function. In most cases, males tended to have more pronounced sway, as indicated by the speed and amplitude aspects of the movement of the center of pressure during the force platform registrations and these differences were larger in the older age groups. In contrast, in the field test a larger proportion of males were able to achieve the highest category (10 s in tandem stand) and the proportion of subjects unable to stand for a minimum of 10 s feet side by side was larger among females than males. These observations may partly be due to differences in the participation/acceptable performance in the different tests. In addition, the field test and force platform measurements may partially reflect different aspects of balance abilities.
Conclusion: The results of the present study provide normative values for force platform balance tests at an age of 30 years and above. Deterioration in balance function clearly starts at relatively young ages and further accelerates from at about 60 years upwards. Due to systematic differences between males and females, separate normative values for both sexes are needed. Due to marked ceiling effects the field test can only be recommended for older individuals, aged >/=60. On the other hand, force platform registrations in the more demanding tests (semi-tandem and tandem stands) suffer from floor effects in the oldest age groups.