Specific neurobiological link identified between hearing loss and cognitive decline

Presbycusis is a prevalent form of age-related hearing loss that also hinders speech recognition. While scientists have linked hearing loss to an increased risk of cognitive decline, the biological "bridge" between the two has remained unclear. New from eNeuro, researchers at Tiangong University and Shandong Provincial Hospital, led by Ning Li, explored the link between these symptoms in people. 

The researchers identified a specific neurobiological link between hearing loss and cognitive decline called the Functional-Structural Ratio (FSR). They found that the putamen and fusiform gyrus (involved in processing sound and speech) and the precuneus and medial superior frontal gyrus (involved in memory and decision-making) become less connected to functional brain networks in those with presbycusis. These reduced connections to networks were directly associated with worse hearing thresholds and poorer performance on memory and executive function tests. 

According to the authors, these findings suggest that hearing loss involves a coordinated decline in both brain structure and function, which may contribute to the symptoms of the disorder. Says Li, "The most important takeaway is that preserving hearing health may protect brain integrity. Because changes in the FSR correlate with both hearing loss and cognitive decline, this ratio could eventually serve as a biomarker-a tool for doctors to identify who is at the highest risk for dementia simply by looking at their brain scans."