Brain structural reorganization mediates the relationship between hearing loss and cognitive impairment

Presbycusis is a common disease in the elderly linked to cognitive decline. Studies have shown structural alterationsin brain regions associated with hearing and cognitive function in presbycusis patients. However, the neural mechanisms linking brain structure with hearing loss and cognitive impairment remain unclear. This study investigated neuroanatomical alterations associated with auditory and cognitive functions. A total of 67 presbycusis patients and 68 normal-hearing controls underwent magnetic resonance imaging, auditory assessment, and cognitive assessment. Presbycusis patients were divided into presbycusis cognitive preservation (presbycusis-CP) and presbycusis cognitive impairment (presbycusis-CI) subgroups according to Montreal Cognitive Assessment scores. Atrophy of gray matter volume (GMV) was observed in presbycusis patients. The results indicated that GMV of the hippocampus, superior frontal cortex (SFC), and posterior cingulate cortex (PCC) mediated the connection between hearing loss and cognitive impairment. Interestingly, the hippocampus mediated the relationship between the GMV of the SFC and PCC in presbycusis and with the strongest mediating effect (56.14%) in presbycusis-CI patients. Notably, this was not valid in normal-hearing controls and presbycusis-CP patients. Overall, presbycusis patients, especially presbycusis-CI patients, show a specific reorganization pattern of auditory and cognitive-related brain areas and that the hippocampus may be a specific target for presbycusis-related cognitive impairment.