Body-sway characteristics during a static upright posture in the elderly.

AIM This study aimed to determine the reliability and sex and age-level differences of body-sway parameters, based on center of pressure (COP) measurements, during a static upright posture in the elderly and to clarify their body-sway characteristics in comparison with those of young adults. METHODS The subjects were 50 healthy elderly and 50 healthy young adults. They had no evidence or known history of disorder. The data sampling frequency was 20 Hz. Thirty-six highly reliable parameters were selected from the following seven domains: distance; position; distribution of amplitude; area; velocity; power spectrum; and vector. In addition, four body-sway factors (unit time sway, front-back sway and a left-right sway and the high-frequency band power) were also measured. RESULTS In the elderly, most body-sway parameters had very high reliability and did not show significant sex or age-level differences. The degree of body sway was greater in the elderly than in young adults, and marked differences were found, especially in sway velocity and periodicity. The four body-sway factors showed almost the same tendency as the 32 sway parameters. CONCLUSION We judged that the body sway in the elderly showed large individual differences. Approximately 10% of the elderly subjects may be outside the standard range as compared to young adults, mainly in parameters relating to velocity and spectrum. Because the body-sway characteristics of the elderly are considerably different from those of young adults, we may need unique criteria to evaluate their body sway.