Abstract
Impairments of balance predispose older people to falls. Some cognitive functions, especially executive functioning have been shown to affect balance and discriminate fallers from non-fallers. Mental flexibility is a component of the executive function and comprises multiple cognitive processes that work together to adjust the course of thoughts or actions according to the changing demands of a situation without the use of explicit instructions. However, the role of mental flexibility in balance in older people remains unclear. The study aim was to examine the relationship between mental flexibility and falls in a cohort of 212 older people (80.6 ± 4.9 years; 62% female). We hypothesized that: (i) participants with impaired balance would have worse mental flexibility compared to those with good balance; and (ii) poor mental flexibility would predict falls in the sub-group with impaired balance. Balance performance was assessed by measuring postural sway while standing on a medium density foam mat with eyes open for 30 s. Mental flexibility was assessed using a computerized short-form of the Wisconsin Card Sorting Test (WCST; 64 cards) with its sub-components comprising general performance, perseveration, failure-to-maintain set and conceptual ability. Falls were measured prospectively for 12-months using monthly calendars. MANCOVA revealed that WCST performance was associated with balance [Wilks’ Lambda = 0.883, F = 2.168; p = 0.013, partial eta squared () = 0.061] due primarily to reduced concept formation ability [F(2,207) = 5.787, p = 0.004, = 0.053]. Negative binomial regression analysis adjusting for age, education, contrast sensitivity, proprioception, inhibition, and inhibitory choice stepping reaction time (iCSRT) revealed that lower concept formation ability was predictive for falls [Incidence Rate Ratio 1.048 (95% confidence interval 1.016–1.081)]. Further, lower concept formation ability partly explained the association between balance and falls: i.e., fallers in the upper balance tertile had reduced concept formation performance whereas non-fallers had similar concept formation performance across the three balance tertiles. These findings suggest that poor mental flexibility affects the ability to maintain steady balance contributing to increased risk of falls in older people.
Highlights
There is growing evidence for interrelationships between balance and cognition in older people and their associations with falls (Schäfer et al, 2006; Yogev-Seligmann et al, 2008)
Impaired balance has been consistently identified as a risk factor for falls in older people (Lord et al, 2007), with objective balance measures being good markers of fall risk that can be administered in clinical practice (Horak et al, 1989; Piirtola and Era, 2006; Sturnieks et al, 2011)
Mirelman et al (2012) demonstrated that poor executive function, especially inadequate response inhibition, predicts falls in well-functioning older people, and Anstey et al (2009) found subtle differences in inhibition are an early marker of increased fall risk, while multiple cognitive domains are impaired in recurrent fallers
Summary
There is growing evidence for interrelationships between balance and cognition in older people and their associations with falls (Schäfer et al, 2006; Yogev-Seligmann et al, 2008). Executive functions have been associated with increased fall risk in older people (Anstey et al, 2009; Hsu et al, 2012; Mirelman et al, 2012). Mirelman et al (2012) demonstrated that poor executive function, especially inadequate response inhibition, predicts falls in well-functioning older people, and Anstey et al (2009) found subtle differences in inhibition are an early marker of increased fall risk, while multiple cognitive domains are impaired in recurrent fallers. We have shown that slow inhibitory choice stepping reaction time (iCSRT), a test of combined inhibition and rapid step initiation, was predictive of falls in older people and that this association was not mediated by body sway, processing speed or attention (Schoene et al, 2017)
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