Neurocognitive assessment in relation to hearing impairment and retinal neurodegeneration.

Purpose: Sensory impairments are significant contributors to cognitive dysfunction, but the relationship between cognitive decline and various forms of neurosensory degeneration remains poorly understood. This study aimed to evaluate retinal layer neurodegeneration and hearing impairment in the general Korean population using cognitive assessments.

Methods: This cross-sectional, retrospective study included participants who underwent Optical Coherence Tomography (OCT), Pure Tone Audiometry (PTA), and the Mini-Mental State Examination (MMSE). Participants were categorized into three groups based on MMSE scores: control group (MMSE > 27), mild cognitive impairment (MCI, MMSE 23-27), and dementia group (MMSE < 23). PTA thresholds were computed using the weighted four-frequency average formula (0.5 kHz, 1 kHz, 2 kHz, and 4 kHz). OCT images were analyzed to measure the Ganglion Cell Inner Plexiform Layer (GC-IPL), Peripapillary Retinal Nerve Fiber Layer (ppRNFL), and total macular thickness. These sensory parameters were compared across the three groups.

Results: A total of 196 participants were included, with a mean age of 67.0 ± 10.4 years. MMSE scores showed an inverse correlation with both age and PTA thresholds, and a positive correlation with OCT parameters (all P <.05). After adjusting for age, significant differences in PTA thresholds were observed across all groups. However, significant reductions in OCT parameters and best-corrected visual acuity were only seen in the dementia group compared to the control and MCI groups (all P <.05).

Conclusions: Sensory assessments are reliable indicators of cognitive function, with hearing loss emerging as a more consistent and sensitive predictor of early functional decline than retinal thickness measurements. Advanced stages of cognitive impairment are closely linked to retinal neurodegeneration and visual impairment, underscoring the importance of careful monitoring and early intervention.