POSTURAL BALANCE AND ITS SENSORY-MOTOR CORRELATES IN 75-YEAR-OLD MEN AND WOMEN - A CROSS-NATIONAL COMPARATIVE-STUDY

Background. There are no earlier cross-national comparative studies an alyzing the functioning of the posture control mechanisms and its sens ory-motor correlates in elderly subjects. We investigated whether ther e are differences in balance between elderly subjects living in differ ent geographical areas, and analyzed the sensory-motor associates of b alance in men and women separately. Method. Using a force platform met hod, the functioning of the posture control system under three standar dized conditions (normal standing, eyes open; normal standing, eyes cl osed; and tandem standing, eyes open) was studied among samples of 75- year-old residents in three Nordic localities, namely Glostrup in Denm ark, Goteborg in Sweden, and Jyvaskyla in Finland. The associations of the variables describing performance in each test with other sensory and motor functions were studied using correlation analyses and multiv ariate regression models. Results. Differences between the populations were observed in both tests with visual control, favoring the partici pants from Glostrup and Jyvaskyla compared with those from Goteborg. H owever, only minor differences between the subjects from different loc alities were observed in the test performed with the eyes closed. In a ll localities there was a primary sex difference in favor of the women which, however, mainly disappeared when body height was taken into th e analyses as a covariate. A good performance in the balance tests (bo dy 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 positive ly associated with good performance in the balance tests. Among the wo men, a poorer balance was observed in women with a smaller body mass. The results of the multivariate analyses showed that among the men, th e most important predictors of good performance in the balance tests w ere low vibrotactile threshold on the foot, high isometric hand grip s trength, and low body stature. Among the women, the most important pre dictors were low body stature, high body mass, high isometric body ext ension strength, and high psychomotor speed. However, only a small pro portion of the variance in balance (about 13% in the men and 11% in th e 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 localit ies could be detected in some of the tests. The better performance of the women in the balance tests may partly be explained by anthropometr ic factors, especially differences in body height. There may also be d ifferences in the sensory-motor associates of balance in elderly men a nd women. On the basis of the associations observed, it is difficult t o explain the differences in balance between the sexes or subjects liv ing 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.