suggest that the two are interconnected. This concept is well substantiated in current literature, which demonstrates a strong association between executive functioning and falls (Kearney, Harwood, Gladman, Lincoln, & Masud, 2013; Montero-Odasso & Speechley, 2018). The degradation of gait performance in dual-task, as compared to single-task, conditions has been repeatedly demonstrated in normal and cognitively impaired older adults (Allali & Verghese, 2017; Mesbah, Perry, Hill, Kaur, & Hale, 2017). Generally, a superimposed cognitive task (e.g., naming animals, counting backwards) will have a more substantial impact on gait than a physical task (e.g., carrying a glass of water). Vidoni, Thomas, Honea, Loskutova, & Burns (2012) demonstrated altered corticomotor function with simple motor task performance early in the course of AD. It is not clear if this altered, more widespread pattern of motor recruitment is related to inefficiency or compensation, but the authors suggest that this may explain degradation in performance related to dual tasking in individuals with AD, in that the altered motor recruitment for single tasks may leave limited resources for more complex dual tasks.
In comparison to cognitively intact older adults, individuals with dementia often demonstrate exaggerated gait findings, including gait that is slower and more variable than their age- matched peers (Bridenbaugh & Kressig, 2014; Mc Ardle et al., 2017). A safe and skillful gait requires some level of executive functioning. In neurological physical therapy, there was much excitement in the 2000s related to the new use of partial body weight supported treadmill training and the ability to exploit spinal cord central pattern generators (CPGs) to facilitate walking on a treadmill without higher cortical control (i.e., in the presence of spinal cord injury). Functional ambulation in a busy or complex environment cannot be driven by CPGs alone and requires higher cortical activity in the form of executive functions, including planning, divided attention, judgment, problem solving, and cognitive flexibility. Montero- Odasso, Verghese, Beauchet, & Hausdorff (2012) developed a schematic demonstrating the integration of gait and cognition degradation with age (Figure 3). Their model acknowledges that cognitive impairment and gait impairment have historically been viewed across separate and distinct continua, but they
Figure 3: Relationship Between Gait and Cognition
(A) shows a traditional conceptual model of parallel decline of gait and cognition. (B) shows the current interrelated model of decline of gait and cognition.
Note . From Montero-Odasso, M., Verghese, J., Beauchet, O., & Hausdorff, J. M. (2012). Gait and cognition: A complementary approach to understanding brain function and the risk of falling. Journal of the American Geriatrics Society, 6 0(11), 2127-2136. Copyright 2012 by John Wiley & Sons. Used with permission.
Postural control, balance, and falls Research has consistently shown postural control impairment in persons with MCI and dementia, and this is well represented in review studies (Cieślik, Jaworska, & Szczepańska-Gierach, 2016; Mesbah et al., 2017). Degree of postural instability increases as level of cognitive impairment increases, although supportive data for this is primarily in the form of cross-sectional studies as opposed to longitudinal studies. Early in MCI, force plate analysis or computerized posturography may be necessary to identify subtle postural control deficits; as cognitive decline progresses, postural dysfunction is evident on clinical tests (e.g., Berg Balance Scale). The importance of visual input to support upright posture in older adults with cognitive deficits is apparent; that is, eyes closed conditions lead to exaggerated instability as related to age-matched cognitively intact peers. Additionally, and not surprisingly, dual task/divided attention conditions have the same effect, resulting in amplified postural instability. A recent publication by Szczepańska-Gieracha, Cieślik, Chamela- Bilińska, and Kuczyński (2016) confirmed these review study findings and also studied the impact of providing visual feedback in static stance (i.e., standing on a force plate and looking at an eye-level monitor, participants were instructed to keep the Apraxia Apraxia presents as difficulty planning and executing desired motor tasks in the absence of blatant motor or sensory system dysfunction and can substantially impact daily functional tasks. This is usually assessed through observing the pantomimed use of tools or objects and the performance of meaningful and nonmeaningful gestures. A comprehensive literature review on apraxia in AD reveals that, despite the fact that apraxia had long been a diagnostic component for AD, it is not well understood
screen image of their center of pressure within a central square). While this use of visual feedback improved postural stability for the cognitively intact control group, it had the paradoxical effect of decreasing stability in the cognitively impaired group. It is unclear if this was due to the added cognitive burden of the task or an underlying disturbance in the balance control system. Community-dwelling older adults with dementia fall two to three times more frequently than their cognitively intact age- matched peers and are more likely to be hospitalized and experience greater morbidity and mortality associated with falls (Finkelstein, Prabhu, & Chen, 2007; Frytak et al., 2008; Shaw, 2002; Tinetti, Speechley, & Ginter, 1988). The etiology of falls in individuals with dementia is complex and multifactorial. Decreased gait performance (specifically decreased speed and increased variability) and balance impairment are significant risk factors for falls in older adults with AD and other dementias (Allali & Verghese, 2017; Dolatabadi, Van Ooteghem, Taati, & Iaboni, 2018). Other risk factors include history of falls, use of an assistive device, increasing age, and psychotropic drugs (Fernando, Fraser, Hendriksen, Kim, & Muir-Hunter, 2017). or sufficiently studied (Lesourd et al., 2013). Dementia severity is considered a primary risk factor for apraxia; studies have consistently demonstrated increasing prevalence of apraxia with progressive levels of dementia (Smits et al., 2014; Stamenova, Roy, & Black, 2013). Clinicians need to recognize that one in three individuals with AD may present with apraxia (Ozkan, Adapinar, Elmaci, & Arslantas, 2013; Smits et al., 2014). The ability of patients to imitate an activity demonstrated by the
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