Gender-difference in the relationship between postural sway and body factors during quiet standing in the elderly

The aim of this study was to investigate the relationship between postural sway and body factors (height, weight, and base of support) and their possible gender-difference during quiet standing in elderly subjects. A total of 46 elderly subjects (23 men and 23 women) performed quiet standing in feet-together and natural stances on a force platform. As outcome measures, mean distance (MD), total power (TP), and 95% power frequency were derived from the center of pressure (COP) trajectory. Correlations between body factors and outcome measures were investigated in each gender, and the gender-difference of the correlations was identified. Also, stepwise multiple regressions were performed to recognize the major determinants (among body factors) of the outcome measures in each gender. Significant gender-differences were observed in the correlation of the outcome measures with body factors. In case of the feet-together stance, postural sway size (MD and TP) increased with weight in men, but not in women. In case of the natural stance, 95% power frequency of sway increased with base of support (BOS) in men, but not in women. Stepwise multiple regressions revealed that weight in the feet-together stance and BOS in the natural stance were the major determinants of outcome measures, and that their influence on outcome measures differed between genders. Relationships between postural sway and body factors differed between genders in the elderly. These results suggest that elderly men and women may have different postural control strategies related to body factors and the normalization of the postural sway variables by body factors may not be performed in the same way in elderly men and women.