INTRODUCTION: Recent studies implicate the effect of vestibular loss on cognitive decline, including hippocampal volume loss. As hippocampal atrophy is an important biomarker of Alzheimer′s disease, exploring vestibular dysfunction as a risk factor for dementia and its role in hippocampal atrophy is of interest. METHODS: Hippocampal and whole-brain MRI volumes were compared in adults aged between 55 and 83 years: (1) to substantiate previous literature, bilateral vestibulopathy (BV) was compared to healthy controls, (2) to correct for a potential confounding effect of concomitant hearing loss, BV was compared to healthy controls matched on age, sex, and hearing status, (3) to additionally evaluate the isolated effect of hearing loss on brain structure, sensorineural hearing loss (SNHL) was compared to healthy controls. Furthermore, to delineate otolith influence on hippocampal volume in preserved vestibular function (healthy controls and SNHL combined), saccular function was investigated. RESULTS: Whole-brain and targeted hippocampal approaches using volumetric and surface-based measures yielded no significant differences in either of three comparisons: (1) BV versus controls, (2) BV versus matched controls, and (3) SNHL versus controls. Binary support vector machines were unable to classify inner ear health status above chance level. Otolith parameters were significantly associated with hippocampal volume in preserved vestibular function. CONCLUSION: No significant differences in whole-brain or hippocampal volume were found when comparing BV with healthy controls, nor did concomitant SNHL confound this relationship. Otolith function may be associated with hippocampal volume rather than lateral semicircular canal integrity. Future BV studies should generally incorporate otolith function testing.

The authors have declared no competing interest.

https://bmjopen.bmj.com/content/10/9/e039601.long

This work was supported by an Fonds voor Wetenschappelijk Onderzoek (FWO) Fundamental Research Project (Grant Number G042819N3).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics committee of the University Hospital of Antwerp, Belgium gave ethical approval for this work. (EC number B300201938949)

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.

Yes

The data that support the findings of this study are available from the corresponding author upon reasonable request.