Effect of aging on human postural control during cognitive tasks.

The purpose of this study was to investigate the effect of aging on human postural control during cognitive tasks. Forty-eight subjects between the ages of 20 to 60 years underwent a series of balance tests that placed increasingly more demand on sensorimotor and cognitive mechanisms. Balance tests were based on a dynamic posturography device called EquiTest. The standard clinical protocol consisted of assessing the subject's stability in six different sensory conditions as the inputs from the proprioceptive and visual systems were altered in a systematic manner. The subjects were also tested with the head extended backwards. This represents an additional sensory condition in which the input from the vestibular system is modified. In order to investigate the role of cognitive function on the postural control mechanisms, the balance tests were performed either with or without an attention-demanding task. The test sequence was randomized to account for simple order effects. The relative contribution and interaction of sensory modification, cognitive tasking, and age were assessed. The results showed that head extension significantly increased postural sway in sensory conditions in which the proprioceptive input was altered. The effects of cognitive tasking and age group assignment were only approaching significance.