Correlates of dual task cost of standing balance in individuals with multiple sclerosis
Introduction
Deficits in balance and cognition represent two prevalent impairments in individuals with multiple sclerosis (MS) [1], [2]. Balance dysfunction denotes one of the earliest reported symptoms in cases of MS and has been observed even in the absence of clinical disability [3], [4]. Similarly, cognitive impairments also arise early in the disease process and occur in approximately 50% of individuals with MS [5].
Traditionally, balance impairment in MS was believed to be influenced mainly by physiological factors including visual, somatosensory and vestibular impairments; muscle weakness; and spasticity [6], [7]. However, recent evidence suggests that balance in individuals with MS can also be negatively affected by the addition of a concurrent cognitive task (i.e. dual task) [4], [8], [9], [10]. These alterations in postural control while engaged in a cognitive task are indicative of cognitive–motor interference. Commonly, cognitive–motor interferences is quantified as dual task cost (DTC) by calculating the percentage change in outcome measures from single task performance to dual task performance.
Cognitive–motor interference, especially during balance tasks, represents an important topic of scientific inquiry as it has been linked to falls in clinical populations [11], [12]. Specific to MS, a recent study revealed that DTC of walking is associated with physiological fall risk [13]. Due to the potential link between cognitive–motor interaction and falls, DTCs of standing balance represent a potentially important rehabilitation target. In order to maximize the potential for successful rehabilitation, the underlying mechanisms of DTC in balance need to be identified.
The factors related to DTC in upright balance for individuals with MS are relatively unclear. One small study (n = 13) found evidence that DTCs during balance tasks were related to self-reported fatigue [14] while another [8] determined the DTC of standing balance in individuals with MS was not related to disability level. Additionally, walking function and cognitive processing speed are associated with DTC of walking in MS [15], [16]. Consequently, the purpose of the current study was to identify the correlates of DTC of standing balance in individuals with MS. We examined the relationship between demographic, cognitive and clinical balance measures to DTC of standing balance. Based on previous literature [14], [15], [16], [17] we hypothesized that the DTC of posture would be related to balance, cognitive function, fatigue and physiological fall risk.
Section snippets
Participants
This cross-sectional investigation utilized a convenience sample of 62 community-dwelling individuals with a neurologist confirmed diagnosis of MS who participated in an ongoing fall prevention program. Participants had to be over the age of forty, fallen in the previous year, be relapse free for 30 days and be able to stand independently for 30 s.
Procedures
All procedures were approved by the local Institutional Review Board. After arrival at the testing facility participants were informed of the testing
Results
Overall the sample consisted of 46 females and 16 males. Age ranged from 42 to 76 years with a mean of 60.9 years (SD = 7.2 years). Self-reported disability (SR-EDSS) ranged from 0 to 7 with a median value of 6 (IQR = 2). 25 participants required no assistive devices, 21 walked with a cane and 16 utilized a walker for community ambulation. The sample was relatively well educated with all participants having graduated from high school and 68% of participants having completed college degrees.
Discussion
This investigation is the most comprehensive examination of correlates of DTC of standing balance in individuals with MS to date. Despite the large range of disability, balance function, cognitive function, fatigue, and spasticity in the current sample, no correlates of DTC of standing balance were observed. However, postural sway in and of itself was found to relate to clinical balance assessments, fall risk, fatigue and disability level. Postural sway while engaged in a simultaneous cognitive
Conclusion
Overall the observations of this study suggest that the change in standing balance with the simultaneous performance of cognitive task offers minimal clinical information in individuals with MS. In contrast, static balance was found to relate to clinical measures of balance, physiological fall risk, and self-reports of fatigue and disability. Cognitive processing speed and age were only related to standing balance in the dual task condition, but not to the change in performance with the
Acknowledgements
This study was funded through grants from the Consortium of Multiple Sclerosis Centers and National Multiple Sclerosis Society (IL Lot NMSS 006), who took no role in experimental design or manuscript preparation.
References (31)
- et al.
Cognitive impairment in multiple sclerosis
Lancet Neurol
(2008) - et al.
Clinical tests of standing balance: performance of persons with multiple sclerosis
Arch Phys Med Rehabil
(2000) - et al.
Risks of falls in subjects with multiple sclerosis
Arch Phys Med Rehabil
(2002) - et al.
Postural control in multiple sclerosis: effects of disability status and dual task
J Neurol Sci
(2012) - et al.
The effects of cognitive loading on balance control in patients with multiple sclerosis
Gait Posture
(2011) - et al.
Evaluation of postural balance control in patients with multiple sclerosis-effect of different sensory conditions and arithmetic task execution. A pilot study
Neurol Neurochir Pol
(2010) - et al.
Attentional demands for postural control: the effects of aging and sensory reintegration
Gait Posture
(2001) - et al.
Attention and the control of posture and gait: a review of an emerging area of research
Gait Posture
(2002) - et al.
Dual task cost of walking is related to fall risk in persons with multiple sclerosis
J Neurol Sci
(2013) - et al.
Falls in people with multiple sclerosis who use a walking aid: prevalence, factors, and effect of strength and balance interventions
Arch Phys Med Rehabil
(2013)