Effect of anxiety on antero-posterior postural stability in patients with dizziness

The purpose of this study was to investigate the effect of anxiety on the postural stability of a variety of dizzy patients during upright standing. To address this issue, 54 patients complaining of dizziness were enrolled in this study. The degree of anxiety in patients was evaluated on the basis of a routine vestibular examination together with their dizziness handicap inventory (DHI) scores as well as the hospital anxiety and depression scale (HADS). The patients were divided into 3 groups. If there was no vestibular dysfunction, they were defined as psychogenic (PSY) (N=16). The remaining subjects were further divided on the basis of their HADS score. If the score of A (anxiety) was less than 5, they are defined as organic (ORG) (N=25), and the rest were defined as a combination of psychogenic and organic (PSY+ORG) (N=13). Posturographic measurements were performed in a quiet and stable standing position on a force platform, as one of the vestibular examinations. The total length, the area of body sway, and the ratio of maximum perturbation of antero-posterior axis (A/P ratio) were registered. Spectrum analyses of the left-right axis and antero-posterior axis were also performed by using the fast Fourier transform (FFT) method of body sway. We found a significant correlation between anxiety and postural instability in the antero-posterior axis in all subjects as a group and in either group PSY or PSY+ORG. However, no significant correlation was found in group ORG. Using power spectrum analysis (FFT), we identified 3 frequency components of postural sway: group A (0.02-0.21Hz), group B (0.22-2.01Hz), and group C (2.01-10Hz). Statistical significance of the data was examined by ANOVA. Group C reflected somatosensory inputs, and group A reflected vestibular inputs. The power of group C decreased in the high anxiety group, whereas the power of group A increased in the high anxiety group. These phenomena disappeared in the eyes-closed condition. Our study shows that the effect of visual input on vestibular and somatosensory input is affected by anxiety. In conclusion, our results indicate that anxiety affects the postural perturbation in the antero-posterior axis and that anxiety possibly affects the interactions of visual inputs with vestibular and somatosensory inputs in the maintenance of postural balance in patients complaining of dizziness.