Age-dependent differences in the time course of postural control during sensory perturbations

With research demonstrating that older adults are more likely to sustain a loss of balance than younger adults, the need for an account of age-related differences in postural control is apparent. Several measures of balance reported in the literature have assessed balance using an average or summative measure over the course of a trial, typically lasting several seconds. One limitation related to these measures is the inability to assess the time-course of postural control occurring throughout the trial. To this end, the current investigation assessed the temporal changes in balance both as a function of age and sensory environment. Postural control was assessed from 10 older adults (69.3+/-4.7 years) and 10 younger adults (22.1+/-1.7 years) over the course of fifteen seconds in three different sensory environments. The sensory manipulations involved sway-referenced rotation of the floor and/or the visual surround. Significant differences (p=0.001) in overall postural stability were observed between the two groups on all three sensory conditions. Additionally, time-course changes were observed between the two groups when the environment did not cause sensory conflict (sway-referenced floor or room only). However, when the environment created a situation of sensory conflict (sway-referenced floor and room) both groups followed the same time-course of postural changes. Interestingly, the time course of postural control for the older adults on the easiest condition was mimicked by the younger adults on a more challenging condition. However, when faced with sensory conflict there were no group differences in the time course of postural control. The findings suggest an age-related decline in the temporal control of posture in altered sensory environments.