The impact of anxiety on postural control: CO2 challenge model

Abstract

Anxiety and balance and postural control are linked via common neural pathways, such as the parabrachial nucleus network. A laboratory-based model of general anxiety disorder (GAD) using the CO₂ challenge, has potential to be used to observe this relationship, potentially mimicking subjective, autonomic, and neuropsychological features of GAD. The current feasibility study used the CO₂ challenge to explore postural control changes in healthy adults. It was predicted that during the CO₂ condition, participants would show increased postural sway path length and decreased sway stability, compared with a normal air breathing condition. To assess this, heart and breathing rate, quiet standing postural sway path length, sway dynamic stability, and subjective measures of emotion were measured either before and after or during and after the inhalation conditions. Results demonstrated that CO₂ inhalation led to both an increase in sway path length and reduced sway stability compared to the air breathing conditions; the effect on sway path lasted after the inhalation of CO₂ had ceased. Additionally, replication of HR and subjective measures of emotion were observed when comparing air and CO₂ conditions. This provides experimental evidence that CO₂ inhalation can affect balance, suggestive of shared mechanisms between anxiety and balance performance, as well as indicating that the CO₂ model of GAD is suitable to look at changes in balance performance in healthy adults. Future use of this model to explore factors that can reduce the influence of GAD on balance would be beneficial as would a more detailed exploration of the neural pathways associated with the associated comorbidity.

Keywords: CO2 challenge; anxiety; balance control; heart rate; motor control; psychophysiology.

FIGURE 1

Bar chart (with standard error bars 2±) showing the mean scores in each condition for the 2‐way ANOVA of sway change in the anterior–posterior directions. *p < .05; **p < .01; BPM, breaths per minute; O₂, typical air; CO₂, 7.5% CO₂ enriched air.

FIGURE 2

Bar chart (with standard error bars 2±) showing the mean scores in each condition for the 2‐way ANOVA of sway change using the Lyapunov exponent in the y‐axis (LyE). *p < .05; **p < .01; BPM, breaths per minute; O₂, typical air; CO₂, 7.5% CO₂ enriched air.

FIGURE 3

Bar chart (with standard error bars 2±) showing the mean scores in each condition for the 2‐way ANOVA of breathing rate (BPM) *p < .05; **p < .01; BPM, breaths per minute; O₂, typical air; CO₂, 7.5% CO₂ enriched air.