Age differences in postural stability are increased by additional cognitive demands.

We report an investigation of postural stability in two groups of volunteers (mean ages of 57 and 77). Participants were required to stand on a force platform while performing five cognitive tasks: (1) random digit generation, (2) Brooks' spatial memory, (3) backward digit recall, (4) silently counting from 1-100, and (5) counting backward in threes (aloud). There was also a control condition in which there was no cognitive task. Postural stability was adversely affected by age in all conditions. Moreover, the difference between the two age groups was significantly greater when performing tasks 2 and 3, in comparison with the age difference in the control condition. Regression analyses revealed that the effect of age on postural stability while performing these particular tasks remained significant even after the following measures were included in the regression: postural stability in the control condition, cognitive performance, intelligence, and speed. We suggest that age differences in postural stability are increased by cognitive tasks requiring use of the visuo-spatial sketchpad component of working memory.