Effect of Hearing Loss and Vestibular Decline on Cognitive Function in Older Subjects: Correlation With Cortical Auditory Evoked Potentials and MRI Brain Volume Changes

The world population has been growing and aging dramatically, with a rising prevalence of dementia. Worldwide, around 50 million people have dementia, with 10 million new cases added every year. Despite the epidemic scale of dementia, until now no cure or disease-modifying therapy has been identified. Therefore, the World Health Organization (WHO) has recognized dementia as a public health priority. Several large studies have demonstrated that hearing impairment is associated with a greater risk of cognitive impairment. Hearing rehabilitation could potentially provide a disease-modifying therapy to delay cognitive decline. Although auditory behavioral research has not yet revealed a reliable indicator of early cognitive impairment, cortical-evoked auditory potentials (CAEP) have shown promising evidence as a non-invasive way to identify early-stage cognitive impairment.

The peripheral vestibular apparatus is located in the inner ear and codes rotation and translation of the head to preserve a stable view. Increasing evidence suggests that bilateral vestibular function loss, also known as bilateral vestibulopathy (BVP), leads to hippocampal atrophy and reduced spatial cognitive skills, as well as structural and functional alterations in parieto-insular and parieto-temporal regions. Many studies have demonstrated that vestibular function declines with age. Vestibular dysfunction can be linked to reduced topographical orientation and memory and has been suggested as a risk factor to AD, due to increased risk of falling and deficits in activities of daily life (ADL).

Our first aim is to study the effect of SNHL and vestibular decline on CAEP, spatial and non-spatial cognitive functioning and trajectories in cognitively healthy older subjects, as well as patients with mild cognitive impairment (MCI) and AD. Our second aim is to study if MRI brain volume changes can be observed in the hippocampus, entorhinal cortex, and auditory and vestibular key regions in these populations and correlate with CAEP and cognitive functioning.

The expected outcome is important to society because it will provide data from a cognitive assessment protocol adapted for a potentially hearing-impaired population, objective outcome measures (incl. CAEP and MRI brain volume changes) to identify older subjects with SNHL and BVP at risk for cognitive decline, and will support screening and interventional studies to assess the impact of rehabilitation on slowing down cognitive decline.