AGE-RELATED DIFFERENCES IN SPATIOTEMPORAL MARKERS OF GAIT STABILITY DURING DUAL TASK WALKING.

Abstract

Purpose/Hypothesis: Increased stride-to-stride variability during walking characterizes gait instability and predicts falling in older adults. Walking while performing cognitive tasks (dual task walking) is also associated with increased risk of falling. The purpose of the study was to examine whether gait velocity and variability in stride velocity differ in older adults compared with middle-aged and younger adults during normal and dual task walking conditions. Subjects: Sixty healthy older (n=20, mean age=81 years), middle-aged (n=20, mean age=48 years), and young adults (n=20, mean age=25 years) participated in the study. All subjects were independent ambulators classified as non-fallers. Materials/Methods: Subjects walked across an instrumented GAITRite® walkway under each of two conditions. In normal walking, subjects walked at self-selected speeds across the walkway. In dual task walking, subjects walked across the walkway while they verbally spelled 5-letter words backward. Three trials were completed in both conditions. Variability in stride velocity was quantified with the coefficient of variation (%CV). Errors in the cognitive task were quantified in the dual task condition. Results: Older subjects walked more slowly (p<.05) than did middle-aged and younger subjects in normal walking (122 ± 23, 148 ± 15 and 146 ± 18 cm/s, respectively) and in dual task walking (97 ± 22, 136 ± 16 and 135 ± 22 cm/s, respectively). Similarly, older subjects walked with greater variability in stride velocity (p<.05) than did middle-aged and younger subjects both in normal walking (6.1 ± 2.0, 3.6 ± 1.5 and 3.9 ± 2.3 %CV, respectively) and in dual task walking (9.0 ± 6.5, 5.1 ± 1.6 and 5.2 ± 3.0 %CV, respectively). Across groups, gait velocity decreased (p<.001) and variability in stride velocity increased (p=.001) in dual task walking. Additionally, in older subjects only, an increase in the number of errors in the cognitive task was associated with reduced gait velocity (r=-.487; p<.05) and increased variability in stride velocity (r=.534; p<.05) during dual task walking. Conclusions: The gait changes observed in dual task walking characterize decreased gait stability and indicate that performing cognitively demanding tasks during walking has a destabilizing effect on gait that is most apparent in older people. Performing cognitively demanding tasks during walking may place older people at greater risk of falling. Clinical Relevance: It is important to recognize that attention-demanding tasks have a destabilizing effect on gait and that attentional processes are involved in walking. Recognizing the potential role of attention-demanding tasks on fall risk, one might instruct older individuals who are at risk of falls to avoid performing cognitive tasks while they are walking. In contrast, one may also recognize the utility of dual tasking and choose to engage the individual in cognitive activities while walking in an effort to improve the person's ability to perform dual tasks in a safe and functional manner.