Abstract
Introduction.
In older adults, dizziness is often experienced as a vague feeling of subjective unsteadiness, where people perceive themselves to be swaying more than they actually are. One factor that potentially drives such distorted perceptions of instability is (hyper)vigilance towards balance. This study aimed to investigate if older adults who report higher levels of trait balance vigilance (i) are more likely to report sensations of general unsteadiness when their balance is acutely threatened, and (ii) if this is accompanied by maladaptive changes in postural control.
Methods.
Forty-eight healthy older adults without vestibular diagnosis (Mean age = 71.0, range = 60–83) completed the recently validated Balance-Vigilance Questionnaire to quantify trait balance vigilance. Participants were fitted a VR headset and completed 60-second, narrow-stance balance trials on a force platform, under conditions designed to create a threatening (standing at a 20-meter virtual height) or non-threatening (virtual ground level) environment. For each condition, we assessed self-reported stability (0-100%) and fear of falling (0-100%), postural control (sway amplitude and frequency), muscular control (tibialis anterior activity), and prefrontal and somatosensory cortical activity using fNIRS.
Results.
Preliminary results are reported. When presented with a postural threat, high-vigilant older adults (Balance Vigilance Score≥18; N=13) reported significantly greater fear of falling (+25%; p=.027) and more reduced perceived stability (-25%; p=.006) compared to low-vigilant older adults – despite there being no differences in actual sway amplitude (p=.157). Only the low-vigilant group showed evidence of an adaptive ‘stiffening’ strategy in response to threat: i.e. increased sway frequency (p=.028) and tibialis anterior activity (p=.027). fNIRS analysis is ongoing.
Conclusions.
These preliminary findings suggest that, in response to a postural threat, older adults with high balance-vigilance are more likely to experience excessive fear of falling and perceptions of instability, and may fail to make adaptive changes to their postural control. Screening for excessive balance vigilance may therefore be recommended.
Comments
Question
Hello and thank you for presenting your work. You conclude that higher-vigilant people are more likely to have fear of falling (which makes sense) but also conclude that those people may fail to make adaptive changes - what are your thoughts about higher vigilant people over-correcting, thereby increasing their risk of falling - e.g. reaching out to grab something to steady themselves, which results in distorting their centre of gravity, before they are safely within reach of the item?
Thank you for that question! Yes we do think that hypervigilance will contribute to overly cautious behaviour as you describe. For instance, a recent study by Castro et al. showed that older people with unexplained dizziness (who we previously found to exhibit greater balance vigilance) have a reduced stepping threshold in response to perturbations.
An explanation for a reduced stepping threshold could be related to our study's finding of greater perceptions of instability coupled to a suppressed automatic stiffening response in high-vigilant individuals. That is, any perturbation will be experienced as more threatening and destabilising, but the lack of automatic stiffening response would also make it more difficult to rapidly counteract such perturbation - thus warranting a step to be taken.
That said, unfortunately vigilance was not directly assessed in the Castro et al study, and in our study we only assessed static balance, so next we now need to look into the role of vigilance in the response/recovery to perturbation of balance.