Background: There are no earlier cross-national comparative studies analyzing the functions of the posture control mechanisms and its sensory-motor correlates in elderly subjects. We investigated whether there are differences in balance between elderly subjects living in different geographical areas, and analyzed the sensory-motor associates of balance in men and women separately.
Method: Using a force platform method, the functioning of the posture control system under three standardized conditions (normal standing, eyes open; normal standing, eyes closed; and tandem standing, eyes open) was studied among samples of 75-year-old residents in three Nordic localities, namely Glostrup in Denmark, Göteborg in Sweden, and Jyväskylä in Finland. The associations of the variables describing performance in each test with other sensory and motor functions were studied using correlation analyses and multivariate regression models.
Results: Differences between the populations were observed in both tests with visual control, favoring the participants from Glostrup and Jyväskylä compared with those from Göteborg. However, only minor differences between the subjects from different localities were observed in the test performed with the eyes closed. In all localities there was a primary sex difference in favor of the women which, however, mainly disappeared when body height was taken into the analyses as a covariate. A good performance in the balance tests (body height-adjusted values) was associated with good visual acuity, low vibrotactile thresholds, and high psychomotor speed. Also, isometric muscle strength, especially hand grip and body extension, was positively associated with good performance in the balance tests. Among the women, a poorer balance was observed in women with a smaller body mass. The results of the multivariate analyses showed that among the men, the most important predictors of good performance in the balance tests were low vibrotactile threshold on the foot, high isometric hand grip strength, and low body stature. Among the women, the most important predictors were low body stature, high body mass, high isometric body extension strength, and high psychomotor speed. However, only a small proportion of the variance in balance (about 13% in the men and 11% in the women) could be explained by the help of these factors.
Conclusions: As the same procedure was applied to the analysis of postural balance, some differences between the populations living in different localities could be detected in some of the tests. The better performance of the women in the balance tests may partly be explained by anthropometric factors, especially differences in body height. There may also be differences in sensory-motor associates of balance in elderly men and women. On the basis of the associations observed, it is difficult to explain the differences in balance between the sexes or subjects living in different localities. Within the sexes, only a small proportion (10-13%) of the variation in balance during normal standing with eyes open could be explained by the factors included in the study.