Hearing impairment and dementia: cause, catalyst or consequence?

The relationship between hearing impairment and dementia has attracted significant attention, the 2024 Lancet Commission report identifying hearing loss as the largest modifiable risk factor for dementia from mid-life. The nature of this linkage between dementia and hearing remains unclear and is likely to be complex. In principle, hearing impairment could cause (directly promote), catalyze (amplify) or be a consequence of neurodegenerative pathology and cognitive decline. Here we use this framework to examine different lines of evidence for the association between hearing impairment and dementia, and consider how this evidence speaks to potential mechanisms and treatment implications. We conclude by considering practical clinical implications for management of patients with hearing impairment and dementia, the potential role for central hearing tests as 'auditory biomarkers' of dementia, and the need for further collaborative and mechanistically motivated research in this area.