Compromising postural balance in the elderly.

BACKGROUND: Additional tasks that are assumed to disturb standing postural control can be divided in added motor or added cognitive tasks. It is unknown which type of task causes the most disturbances of postural control in elderly.

OBJECTIVE: The aim of this study was to determine whether the dual tasking disturbance of postural control in elderly is caused by vocal articulation or by limited attentional resources.

METHODS: 39 elderly (81 +/- 7 years) were tested on a force plate in a two-legged standing position. Seven balance variables were assessed: maximum displacement and standard deviation amplitude in the medial-lateral (ML, SDML) and anterior-posterior (AP, SDAP) direction, average speed of displacement (V) and the area of the 95th percentile ellipse (AoE) and sway path (PL) per given time. The following task combinations were tested: no secondary task, repeating a number aloud (articulation), counting backwards aloud (articulation and attention), and counting backwards silently (attention). All tasks were tested with and without vision.

RESULTS: A factorial ANOVA revealed main effects of additional tasks in PL, ML, SDML, AP, AoE and V. Bonferroni post-hoc analysis in a vision situation showed significant difference between no task and counting backwards aloud task in balance variables ML (p = 0.006), SDML (p = 0.002), AP (p = 0.020) and V (p = 0.003), respectively. All no-vision situations showed no significant difference between the different tasks.

CONCLUSION: The findings suggest that the combined articulation and attention-demanding secondary task stressed the attentional system of elderly to such an extent that it compromised the performance of the primary task (quiet standing). The counting backwards aloud task may be used as dual task for clinical balance assessment in at-risk populations. This task was best able to disturb postural control.