Functional-structural coupling: brain reorganization in presbycusis is related to cognitive impairment

Presbycusis, a prevalent neurodegenerative disorder, is characterized by a decline in speech recognition ability. Recent studies have linked presbycusis with cognitive impairments across multiple domains. However, the underlying neurobiological mechanisms between presbycusis and cognitive impairments remain unclear. We assessed pure-tone audiometry thresholds (PTA), speech recognition thresholds (SRT), and cognitive abilities in individuals with presbycusis (24 males and 31 females) and healthy controls (23 males and 32 females). Using magnetic resonance imaging techniques, we calculated the amplitude of low-frequency fluctuations (ALFF) as a measure of functional characterization and gray matter volume (GMV) as a measure of structural characterization. Based on ALFF and GMV, we calculated Functional-Structural Ratio (FSR) to measure the functional-structural coupling. Significant correlations between GMV atrophy and ALFF changed in the putamen, fusiform gyrus, precuneus, and medial superior frontal gyrus in presbycusis group, and these changes were significantly associated with the increase in PTA and SRT. The FSR reduction in the FFG, precuneus, and medial superior frontal gyrus were also significantly associated with the increase in PTA and SRT. Moreover, it was also significantly correlated with lower scores on the Montreal Cognitive Assessment (MoCA) and the Auditory Verbal Learning Test (AVLT), as well as the prolonged time in the Trail Making Test (TMT-A). Presbycusis involves coupled structural atrophy and functional decline in auditory and higher-order cognitive regions. Crucially, reduced FSR correlates with both worsening hearing thresholds and cognitive impairment. This highlights FSR as a key neurobiological link between hearing loss and cognitive decline. This research provides a novel basis for early screening and dynamic monitoring of presbycusis-related cognitive impairment. Significance Statement This study reveals that age-related hearing loss (presbycusis) involves coupled structural atrophy and functional decline in key brain regions like the fusiform gyrus and putamen. We introduce the Functional-Structural Ratio (FSR) as a novel biomarker showing that reduced brain functional-structural coupling correlates with both worsening hearing thresholds and cognitive impairment. This provides the first direct neurobiological evidence linking hearing loss to cognitive decline via shared neural reorganization. FSR offers a potential tool for early screening and monitoring of dementia risk in presbycusis, highlighting that preserving hearing health may protect brain integrity. These findings advance our understanding of how sensory decline drives neurodegeneration.