Reduced structural connectivity in age-related hearing loss aligns with the sensory deprivation theory

Age-related hearing loss (ARHL) may contribute to cognitive decline through structural degeneration and brain reorganization, as posited by the sensory deprivation theory. These processes can be characterized by topological changes, such as strengthening and weakening of structural connections between brain regions. Stronger connections are more relevant to reorganization, as reorganization is thought to support speech processing by recruiting additional brain networks as a compensatory mechanism. We investigated connectivity changes associated with ARHL to improve the understanding of the sensory deprivation theory. Similar to the lateralization of speech processing, we hypothesized that structural reorganization associated with ARHL would be most evident in the left hemisphere. We assessed whole-brain structural connectivity using 1.5 Tesla diffusion-weighted MRI and structural T1 images in 2402 participants (median age = 66.1 years, females = 54.7%) from the population-based Rotterdam Study. Pure-tone audiometry was performed, and pure-tone averages (PTAs), for different frequency ranges including PTA_low (250-1000 Hz) and PTA_all (250-8000 Hz), were determined for the better-hearing ear to reflect ARHL. ARHL was primarily associated with weaker connections involving frontal and subcortical gray matter regions. Contrary to our hypothesis, no lateralization in the connectivity alterations was observed. PTA_low and PTA_all yielded the strongest associations, likely driven by low-frequency hearing thresholds. Adjusting for cardiovascular risk factors attenuated associations, especially for PTA_low. In conclusion, the findings contradict the hypothesized compensatory structural reorganization expected from the neural effects of sensory deprivation. While the observed weaker connectivity aligns with the sensory deprivation theory, the results also suggest cardiovascular health as a common risk factor.