By Dr Toby Ellmers.
During walking, we rely on visual information to identify tripping hazards and navigate safely through the environment. The way we shift our gaze and scan the environment (visual-search behaviour) is affected by ageing and fall-risk. For example, when navigating obstacles or stepping targets, older adults deemed to be at a high risk of falling will adopt less-variable patterns of visual-search behaviour. Specifically, they will visually prioritise the initial/immediately upcoming stepping target, at the expense of previewing future obstacles or targets. Such restricted visual-search behaviours are hypothesized to impair an individual’s ability to plan future stepping actions and are associated with both reduced stepping safety and increased fall-related anxiety. Researchers have thus proposed that heightened fall-related anxiety may underpin these maladaptive visual-search behaviours in high-risk older adults. We sought to test this hypothesis.
Forty-four older adults walked along a path and stepped into two stepping targets (with raised edges). All participants completed walks at ground level, while participants deemed to be at a low risk of falling (n=24) also completed walks under conditions designed to induce fall-related anxiety (walkway elevated 0.6m; ‘Threat’ condition). Outcome measures included both gaze behaviours and gait kinematics (e.g., stepping accuracy and stance times before target steps). During ground level trials, high-risk participants reported greater fall-related anxiety compared to low-risk participants. As predicted, high-risk participants also visually prioritized immediate walkway areas (1–2 steps ahead), doing so at the expense of previewing future stepping constraints (second stepping target). When controlling for age, cognitive and physical functioning, these ‘high-risk’ visual-search behaviours were significantly correlated with greater attention directed towards consciously controlling walking movements. When completing walks on the elevated walkway, low-risk participants reported increased fall-related anxiety and adopted visual-search behaviours identical to those observed in the high-risk participants at ground level. However, unlike their high-risk counterparts, the low-risk participants appeared capable of adapting their gait to compensate for this restricted visual previewing of the second stepping target. Specifically, the low-risk participants exhibited increased stance durations prior to stepping into the un-previewed second target, thereby acquiring the visual information required for safe negotiation. Consequently, while the restricted visual-search behaviours appeared to negatively affect high-risk participants’ stepping safety (with increased stepping errors observed for the second target in the high-risk group), no such decreases in safety were observed for low-risk participants.
These findings provide evidence of a link between fall-related anxiety and ‘high-risk’ visual-search behaviours. Further research is currently being undertaken to investigate why high-risk older adults, unlike their low-risk counterparts, failed to adapt their stepping behaviours to compensate for these restricted (anxiety-related) visual search behaviours, and thereby experienced reduced stepping safety as a result.
Figure. Comparisons of low- and high-risk participants at Ground, and low-risk participants at Ground and Threat, for duration of fixations (as a % of overall fixations) towards: (A) the immediate walkway and (B) the second target. **p < .01, ***p < .001, data shown as mean ± standard error of the mean. C: Schematic diagram of the walking task.
Ellmers, T. J., Cocks, A. J., & Young. W. R. (2019). Evidence of a link between fall-related anxiety and high-risk patterns of visual search in older adults during adaptive locomotion. The Journals of Gerontology: Series A, Biological and Medical Sciences. Advanced online publication. https://academic.oup.com/biomedgerontology/article/doi/10.1093/gerona/glz176/5541624/