Attentional mechanisms contributing to balance constraints during gait: The effects of balance impairments

Background. Recent research has begun to explore the ability of older adults to perform balance tasks while simultaneously performing a secondary cognitive task; however, it has suffered from limitations regarding the mechanisms underlying the problems that cause dual-task deficits in older adults with balance impairments. Two possible attentional mechanisms (reduced general attentional capacity vs. a true dual-task performance deficit and inability to allocate attention between two tasks) contributing to balance constraints were examined. Methods. Twelve healthy elderly adults and 12 elderly adults with balance impairments (BIOA) were asked to perform obstacle avoidance while walking, either alone or simultaneously with an auditory Stroop task. Two experiments were designed to examine attentional mechanisms that may contribute to reduce performance in the dual-task situations for the BIOA. Results. Experiment 1 determined whether for BIOA, single vs. dual-task performance conditions led to similar effects as a single-task difficulty (congruent vs. incongruent) manipulation. Results indicated that dual-task performance reduction did not exceed that of the difficult single task, suggesting that neither older adult group showed a true dual-task performance deficit, but rather BIOA showed a reduced attentional capacity. Experiment 2 showed that BIOA also showed deficits in flexibly focusing their attention between two tasks according to instructions. Conclusion. Our study confirmed that the ability to allocate attention between a postural task and a secondary cognitive task was impaired in BIOA; it is suggested that inability to flexibly allocate attention could be one important factor among many factors that contribute to balance constraints during gait in fallers. (C) 2008 Elsevier B.V. All rights reserved.