Vestibular Function Predicts Balance and Fall Risk in Patients with Alzheimer's Disease

Background: Patients with Alzheimer's disease (AD) are at high risk for falls. Vestibular dysfunction predicts balance impairment in healthy adults; however, its contribution to falls in patients with AD is not well known. Objective: The objective of this study was to assess whether vestibular function contributes to balance and fall risk in patients with AD. Methods: In this prospective observational study, we assessed vestibular function using measures of semicircular canal (vestibulo-ocular reflex (VOR) gain) and saccular function (cervical vestibular-evoked myogenic (cVEMP) response), and we assessed balance function using the Berg Balance Scale and quantitative posturography. We evaluated falls incidence for a mean 1-year follow-up period (range 3-21 months) in 48 patients with mild-moderate AD. Results: Relative to matched controls, AD patients exhibited increased medio-lateral (ML) sway in eyes-open (0.89 cm versus 0.69 cm; p = 0.033) and eyes-closed (0.86 cm versus 0.65 cm; p = 0.042) conditions. Among AD patients, better semicircular canal function was associated with lower ML sway and antero-posterior (AP) sway in the eyes-closed condition (β= -2.42, 95% CI (-3.89, -0.95), p = 0.002; β= -2.38, 95% CI (-4.43, -0.32), p = 0.025, respectively). Additionally, better saccular function was associated with lower sway velocity (β= -0.18, 95% CI (-0.28, -0.08); p = 0.001). Finally, we observed that better semicircular canal function was significantly associated with lower likelihood of falls when adjusted for age, sex, and MMSE score (HR = 0.65; p = 0.009). Conclusion: These results support the vestibular system as an important contributor to balance and fall risk in AD patients and suggest a role for vestibular therapy.