Association of Unilateral and Bilateral Speech‐In‐Noise Hearing Status With Dementia

OBJECTIVES: Although hearing loss is a well-established risk factor for dementia, previous studies predominantly focused on peripheral hearing sensitivity, overlooking deficits in central auditory processing as measured by speech-in-noise (SIN) testing. This study aims to investigate the association between bilateral SIN hearing loss and the risk of all-cause dementia, and to examine how cognitive reserve (CR) modifies this association. METHODS: We conducted a prospective cohort study utilizing data from the UK Biobank, a large, population-based cohort. Participants were recruited between 2006 and 2010, with follow-up lasting until October 2023. The primary outcome was all-cause dementia, and secondary outcomes included some brain regions of interest. Cox proportional-hazards models were employed to estimate dementia risk and differences in brain volume associated with bilateral SIN hearing status, as well as the interaction between SIN hearing and CR. RESULTS: Of the 72,004 participants, both bilateral hearing loss (HR = 1.507, 95% CI: 1.349, 1.685) and unilateral hearing loss (HR = 1.181, 95% CI: 1.068, 1.305) were associated with higher dementia risk. Bilateral hearing loss was significantly associated with volume in brain regions supporting auditory, including subcortical volumes, regional gray matter volumes, accumbens, hippocampus, central opercular cortex, and heschl's gyrus. Right ear dominance was observed in unilateral mild hearing loss, whereas unilateral severe hearing loss demonstrated left ear dominance. Although dementia risk showed a dose-response relationship according to the level of SIN hearing and CR, there was no evidence that CR significantly moderated the association between SIN hearing and dementia risk. CONCLUSIONS: Our study highlights significant disparities in dementia risk and brain volume based on bilateral hearing status, and hearing conservation strategies should consider hearing status laterality and severity to enhance prevention precision.