Abstract
BackgroundDeterioration of executive functions in the elderly has been associated with impairments in walking performance. This may be caused by limited cognitive flexibility and working memory, but could also be caused by altered prioritization of simultaneously performed tasks. To disentangle these options we investigated the associations between Trail Making Test performance—which specifically measures cognitive flexibility and working memory—and dual task costs, a measure of prioritization.Methodology and Principal FindingsOut of the TREND study (Tuebinger evaluation of Risk factors for Early detection of Neurodegenerative Disorders), 686 neurodegeneratively healthy, non-demented elderly aged 50 to 80 years were classified according to their Trail Making Test performance (delta TMT; TMT-B minus TMT-A). The subjects performed 20 m walks with habitual and maximum speed. Dual tasking performance was tested with walking at maximum speed, in combination with checking boxes on a clipboard, and subtracting serial 7 s at maximum speeds. As expected, the poor TMT group performed worse when subtracting serial 7 s under single and dual task conditions, and they walked more slowly when simultaneously subtracting serial 7 s, compared to the good TMT performers. In the walking when subtracting serial 7 s condition but not in the other 3 conditions, dual task costs were higher in the poor TMT performers (median 20%; range −6 to 58%) compared to the good performers (17%; −16 to 43%; p<0.001). To the contrary, the proportion of the poor TMT performance group that made calculation errors under the dual tasking situation was lower than under the single task situation, but higher in the good TMT performance group (poor performers, −1.6%; good performers, +3%; p = 0.035).ConclusionUnder most challenging conditions, the elderly with poor TMT performance prioritize the cognitive task at the expense of walking velocity. This indicates that poor cognitive flexibility and working memory are directly associated with altered prioritization.
Highlights
The application of dual task paradigms to evaluate the role of executive functioning during walking is generally well-accepted
Under most challenging conditions, the elderly with poor Trail Making Test (TMT) performance prioritize the cognitive task at the expense of walking velocity
This indicates that poor cognitive flexibility and working memory are directly associated with altered prioritization
Summary
The application of dual task paradigms to evaluate the role of executive functioning during walking is generally well-accepted. This seems to be different in Parkinson disease patients [10], in elderly fallers [11], and in Parkinsonian patients who fall regularly [12] They have an increased probability to use a ‘‘posture second’’ strategy, and to prioritize the cognitive task at the expense of the stability of walking. Most of these studies put their focus on the evaluation of the walking task but not on the non-walking task, knowledge about dual-task behaviour of older subjects, in particular with regard to non-walking tasks, is still limited. Deterioration of executive functions in the elderly has been associated with impairments in walking performance This may be caused by limited cognitive flexibility and working memory, but could be caused by altered prioritization of simultaneously performed tasks. To disentangle these options we investigated the associations between Trail Making Test performance—which measures cognitive flexibility and working memory—and dual task costs, a measure of prioritization
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