Presbycusis is age-related hearing loss characterized by a progressive decline in hearing. It accounts for nearly 90% of cases of deafness. Contrary to popular belief, it does not result solely from the decline of the auditory organs, but also involves... auditory cortex lesions.
For about ten years, numerous studies have shown a close association between presbycusis and cognitive decline, to such an extent that researchers have proven that hearing thresholds could be used aspredictive indicators Deficits in executive functions (memory, planning, attention) are also observed. Furthermore, other scientists have demonstrated that hearing loss is the leading modifiable risk factor for dementia. However, the physiological mechanisms underlying this association remained poorly understood… until recently.
Grey matter atrophy and decreased brain activity
A study published in the journal eNeuro has identified for the first time a specific neurobiological link between these two phenomena. To reach this conclusion, researchers from Tiangong University and Shandong Hospital in China examined the hearing and cognition of 110 participants aged 50 to 74. Half of them had presbycusis, while the other half were healthy controls.
To estimate hearing loss, biologists measured pure-tone audiometry thresholds, which are the ability to perceive sounds at different frequencies and intensities, and speech recognition thresholds (the ability to understand spoken words). Then, to quantify cognitive characteristics, they measured spontaneous brain activity using MRI and the volume of gray matter.
“ In patients with presbycusis, atrophy of the grey matter and a decrease in electrical brain activity have been observed., the authors write in their publication, with “ The damage was all the more pronounced the more severe the hearing loss was..
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Regions linked to memory and decision-making particularly affected
More specifically, the functional-structural ratio, calculated from spontaneous brain activity and gray matter volume, made it possible to assess the degree of integration of specific brain regions within functional networks. The results then revealed four particularly affected areas: two involved in sound and speech processing (the putamen and the fusiform gyrus) and two involved in memory and decision-making (the precuneus and the medial superior frontal gyrus).
Thus, according to the authors, " Alterations in cognitive structure and connectivity to functional brain networks in these four areas would explain the symptoms of decline. These results provide the first direct neurobiological evidence linking the hearing loss to cognitive decline via coordinated neuronal reorganization.
Brain areas impacted by neuronal reorganization. The functional-structural ratio (FSR) is lower in patients with presbycusis compared to healthy individuals (NH). Credits: Xiaojie Li et al., 2026.
But how can we explain that hearing loss can have such impacts on the brain? The scientists' hypothesis is that of "auditory deprivation": when the brain stops receiving clear sound signals, the areas responsible for processing this information atrophy and gradually disconnect from the rest of the brain networks.
The impact spreads particularly to areas involved in memory and decision-making, ultimately affecting all cognitive functions. However, researchers qualify this hypothesis. For now, " We cannot rule out that pre-existing brain changes contribute to the observed alterations..
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A new biomarker for cognitive decline
In any case, Ning Li, co-author of the study, welcomes these results with enthusiasm. The main takeaway is that preserving hearing health could protect brain integrity. Since variations in the functional-structural ratio are correlated with both hearing loss and cognitive decline, this ratio could eventually serve as a biomarker – a tool allowing physicians to identify individuals at highest risk of dementia simply by analyzing their brain scans.he said in a statement.
These results also pave the way for a better understanding of how sensory decline induces neurodegeneration.
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