The effect of walking path configuration on gait in adults with Alzheimer’s dementia
Introduction
People with Alzheimer’s dementia (AD) have disturbed walking performance compared to cognitively normal older adults and also have a greater risk for falls and fall-related injuries, such as fractures [1]. Cognitive function plays an important role in the regulation of walking [2] and not surprisingly impaired cognition is associated with increased fall risk in AD [3].
Executive function (EF), a higher order cognitive domain responsible for initiation, planning and attention in goal-directed movements [2], is a key factor in walking. Importantly, impaired executive functioning occurs early in the disease process of AD [4]. People with cognitive impairment have more difficulty performing complex mobility tasks [5,6] and impairment in EF can result in a reduced ability to successfully ambulate in attention-demanding situations such as moving around obstacles, and avoiding falls [7]. Observing people during a gait task while they simultaneously perform a second activity (dual-task paradigm) is an accepted way to assess the interaction between cognition and mobility to provide [8,9] insights into the mechanisms of higher order motor control. Dual-task testing is considered ecologically relevant as most daily activities require the performance of 2 or more simultaneous tasks and represent situations that are likely to lead to falls.
Gait deficits that are sub-clinical in people with AD using standard assessment protocols become observable under dual-task testing of walking in a straight-path while performing a secondary cognitive task [10].However, when people with AD are unable to complete secondary cognitive tasks in dual-task gait testing protocols due to cognitive decline, disease-specific language difficulties or illiteracy, deficits may not be detected in the absence of the added cognitive challenge.
Increasing the complexity of the gait task is another means of evaluating the effect of cognition on performance [5]. Straight path walking provides a low cognitive challenge and may not relate to walking in more complex real-world environments [11]. Whereas, curved path walking reflects real-life situations involving dynamic stability that require individuals to navigate through their environments such as around furniture [11]. The cognitive component within a curved path walking task is thought to be embedded within the task itself [11]. Curved path walking involves planning [12] and greater motor skill and control than straight path walking [12,13], tapping into executive function demands. The use of a complex walking pathway to assess gait for people with AD is a potential solution if people are unable to complete a concurrent cognitive task in a dual-task walking protocol.
Skillful walking can be described as smooth and consistent. Smoothness, a measure of motor control in walking, is a function of the integration of sensory information and coordination of walking. Smoothness deteriorates on curved path walking and is associated with increased falls risk in older adults [14]. Quality of motor control, specifically smoothness, provides meaningful information as walking quickly with poor control is a more adverse gait pattern than walking slowly with good motor control [14]. Therefore, curved path walking may be an avenue to assess not only gait speed deficits but also deficits in motor control for people with AD, providing a better understanding of the relationship between cognition and functional gait deficits.
There is limited research on the effect of path complexity on gait in people with AD. Curved path walking is a simple and inexpensive test that can provide information in multiple areas to identify deficiency in gait and motor control in people with AD. Therefore, the aim of this study was to assess i) the differences in gait performance, and ii) the relationship between cognitive function and time to complete a straight path and curved path walking task in healthy older adults and people with AD. We hypothesized that people with AD will walk slower than cognitively healthy controls in a curved path configuration and executive function will be related to walking speed only on the curved path walking task.
Section snippets
Participants
A total of 14 people with AD and 14 age and sex-matched healthy controls were recruited for this study. Participants with AD were recruited from a day hospital program for people with dementia. Referral to the day program is based on a confirmed diagnosis of dementia by a geriatrician according to the criteria of the National Institute of Neurologic and Communicative Disorders and Stroke-AD and Related Disorders Association (NINCDS-ARDRA) [15]. Healthy controls were recruited from a local
Results
Fourteen individuals with AD and 14 healthy controls completed the study and were included in the analysis. Differences between the groups on demographic information indicated the healthy controls were more physically active than the AD participants. In addition, the two groups differed on all measures of cognitive function, except Digit Span Test – forward. This difference in cognitive function was expected as this defines membership in each group. (Table 1)
Discussion
The present study has demonstrated that people with AD walked significantly slower and had more deficits in the smoothness of their gait in the complex walking path than cognitively healthy older adults. We also demonstrated that higher-order cognitive functions are related to gait performance during the complex walking path in people with AD, which is consistent with existing literature for cognitively healthy older adults [11]. These two findings provide support for the use of the complex
Conflict of interest
None to declare
Acknowledgments
The authors thank Karen Johnson, Director of Alzheimer Outreach Services of McCormick Home; Steve Crawford, CEO, WCA; and the staff and clients at the Alzheimer Outreach Services day program for their hospitality, assistance in organizing this project and participation in the data collection process. This study was funded by the Physiotherapy Foundation of Canada Seniors’ Health Division Research Award in Older Adult Health and had no involvement in the conduct of the study.
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