Motor-cognitive dual-task deficits in individuals with early-mid stage Huntington disease

Highlights

• Individuals with HD experience impairments in simple and complex dual-task ability.

• Simple and complex dual-task ability correlated with cognitive performance.

• Prospective falls were strongly correlated with dual-task performance.

• Dual-task measures evaluate a unique construct in early to mid-stage HD.

• Dual-task measures may have value in improving the prediction of falls risk in HD.

Abstract

Background

Huntington disease (HD) results in a range of cognitive and motor impairments that progress throughout the disease stages; however, little research has evaluated specific dual-task abilities in this population, and the degree to which they may be related to functional ability.

Objectives

The purpose of this study was to a) examine simple and complex motor-cognitive dual-task performance in individuals with HD, b) determine relationships between dual-task walking ability and disease-specific measures of motor, cognitive and functional ability, and c) examine the relationship of dual-task measures to falls in individuals with HD.

Methods

Thirty-two individuals with HD were evaluated for simple and complex dual-task ability using the Walking While Talking Test. Demographics and disease-specific measures of motor, cognitive and functional ability were also obtained.

Results

Individuals with HD had impairments in simple and complex dual-task ability. Simple dual-task walking was correlated to disease-specific motor scores as well as cognitive performance, but complex dual-task walking was correlated with total functional capacity, as well as a range of cognitive measures. Number of prospective falls was moderately-strongly correlated to dual-task measures.

Conclusions

Our results suggest that individuals with HD have impairments in cognitive-motor dual-task ability that are related to disease progression and specifically functional ability. Dual-task measures appear to evaluate a unique construct in individuals with early to mid-stage HD, and may have value in improving the prediction of falls risk in this population.

Introduction

Individuals with HD typically present with a range of motor impairments, including akinesia, bradykinesia, and incoordination [1] that progress over time and affect functional ability. Declines in cognition are a notable feature of the disease process, and people with HD often have difficulty holding, shifting [2] and dividing attention [3]. Difficulty with divided attention, or simultaneously monitoring two tasks, is particularly significant given that automaticity can change with damage to the nervous system; previously automatic movements, such as walking or balancing in standing may become attention demanding [4] and place an increased load on cognitive resources.

Impairments in simultaneous motor-cognitive tasks, i.e. dual-tasks, have been well documented in neurodegenerative disease populations, including Parkinson’s disease (PD) [5], Alzheimer’s disease [6] and multiple sclerosis [7]. In HD, prior studies have shown impairments while performing complex cognitive dual-tasks (competing cognitive tasks with a manual or vocal response) [8] and automaticity with bi-manual tapping tasks (motor-motor dual-task) [9], particularly as task difficulty increases. Guidelines to increase task complexity have not been established; while some have utilized decision-making as the added complexity [10], studies in other populations have utilized inhibitory control of speech [11] to probe executive functioning and task-switching control under dual-task conditions. Although early work demonstrated no relationship among cognitive performance and walking [12], recent work showed that gait speed during motor-cognitive dual-task walking (i.e., walking with backward counting) has been linked with United Huntington’s Disease Rating Scale Total Motor Score (UHDRS-TMS) and performance on cognitive testing [13]. Individuals with greater cognitive impairment also demonstrate greater dual-task interference for complex cognitive tasks [10]. Although individuals with HD can modify their walking speed in response to external cues [12], [14], this ability declines with increasing gait impairment, and the impact of cognitive status on this relationship has not been determined.

Individuals with HD commonly experience falls [15]; in one prospective study, 21% of participants experienced 1 fall and 58% experienced at least 2 falls over the course of a year [15]. Difficulty performing dual-tasks has been associated with falls in people with PD [16] and multiple sclerosis [7]. Falls in HD have been linked with slower walking speed and poorer balance [15], but their relationship with dual-task performance has not been evaluated.

The purpose of this study was to a) examine simple and complex motor-cognitive dual-task performance in individuals with HD, b) determine relationships between dual-task walking ability and disease-specific measures of motor, cognitive and functional ability, and c) examine the relationships of dual-task measures to falls in individuals with HD. We hypothesized that individuals with HD would experience reductions in walking speed under dual-task conditions, and that impairments in dual-task walking would be linked with cognitive performance. We further hypothesized that dual-task assessment would be related to prospective falls.