Abstract
Introduction: Increased variability in motor function has been observed during the initial stages of cognitive decline. However, the natural variability of postural control, as well as its association with cognitive status and decline, remains unknown. The objective of this pilot study was to characterize the day-to-day variability in postural sway in non-demented older adults. We hypothesized that older adults with a lower cognitive status would have higher day-to-day variability in postural sway.Materials and Methods: A Nintendo Wii balance board (WBB) was used to quantify postural sway in the home twice daily for 30 days in 20 non-demented, community-dwelling older adults: once under a single-task condition and once under a dual-task condition (using a daily word search task administered via a Nook tablet). Mean sway distance, velocity, area, centroidal frequency and frequency dispersion were derived from the center of pressure data acquired from the WBB.Results: Linear relationships were observed between the day-to-day variability in postural sway and cognitive status (indexed by cognitive global z-scores). More variability in time-domain postural sway (sway distance and area) and less variability in frequency-domain postural sway (centroidal sway frequency) were associated with a lower cognitive status under both the single- and dual-task conditions. Additionally, lower cognitive performance rates on the daily word search task were related to a lower cognitive status.Discussion: This small pilot study conducted on a short time scale motivates large-scale implementations over more extended time periods. Tracking longitudinal changes in postural sway may further our understanding of early-stage postural decline and its association with cognitive decline and, in turn, may aid in the early detection of dementia during preclinical stages when the utility of disease-modifying therapies would be greatest.
Highlights
Increased variability in motor function has been observed during the initial stages of cognitive decline
More day-to-day variability in postural sway distance and area was related to a lower cognitive status (Table 2, Figures 4, 5), supporting our primary hypothesis
Gait speed variability trajectories across 182 weeks were associated with the severity of mild cognitive impairment (MCI): an initial period of increased variability followed by an accelerated decrease in variability was associated with early-stage MCI, whereas a sustained and gradual decrease in variability was associated with late-stage MCI
Summary
Increased variability in motor function has been observed during the initial stages of cognitive decline. The natural variability of postural control, as well as its association with cognitive status and decline, remains unknown. The objective of this pilot study was to characterize the day-to-day variability in postural sway in non-demented older adults. Cognitive dysfunction is associated with an increased fall risk (Buracchio et al, 2011), it is not known if postural control becomes more variable during the initial stages of cognitive decline. Since this study was designed to target the initial stages of cognitive decline in a high-functioning, community-dwelling cohort, a more sensitive metric derived from extensive cognitive testing was desired. If a change in the neural control of posture is associated with age-related changes in cognitive control, it is likely those postural and cognitive functions share common circuitry or mechanisms (Seidler et al, 2010; Park et al, 2016)
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