Groot, Marius de

AbstractBackgroundRecently, hearing loss has been identified as a promising modifiable risk factor for dementia. Several hypotheses explaining a potential underlying pathway have been proposed, including the sensory deprivation hypothesis, describing a direct causal relationship in which hearing loss leads to neuroplastic changes in the brain. Indeed, hearing loss has been associated with smaller macrostructural brain volumes, which is believed to at least partly explain the association between hearing loss and neurodegenerative disease. However, microstructural changes precede macrostructural changes. Therefore, we aimed to assess the association between hearing loss and microstructural integrity of the brain.Methods1,086 dementia‐free older adults from the Atherosclerosis Risk in Communities (ARIC) study (mean age = 75.2 [SD: 4.9], 61.4% female) underwent hearing assessment (2016‐2017) and magnetic resonance imaging (MRI) of the brain (2011‐2013). Hearing was assessed with pure‐tone audiometry. Microstructural integrity (fractional anisotropy (FA) and mean diffusivity (MD)) of multiple brain regions was determined with diffusion tensor imaging (DTI). Multivariable linear regression models were used to investigate the association between hearing loss and microstructural integrity of the lobes, temporal lobe gyri, medial temporal lobe structures and white matter (WM) tracts, adjusting for relevant confounders.ResultHearing loss was associated with lower WM microstructural integrity in the temporal lobe (difference in SD FA for moderate/severe hearing loss as compared to normal hearing: ‐0.19 [95% CI: ‐0.35, ‐0.03]; and difference in SD MD for moderate/severe hearing loss as compared to normal hearing: 0.15 [95% CI: 0.01, 0.28]). Hearing loss was associated with lower gray matter (GM) microstructure of the hippocampus, but not the amygdala. Moreover, hearing loss was associated with lower WM microstructural integrity of the limbic tracts and the uncinate fasciculus (Figure 1).ConclusionOur results demonstrate that age‐related hearing loss is associated with lower WM microstructural integrity in the temporal lobe, the limbic tracts and the uncinate fasciculus and lower GM microstructure in the hippocampus. These associations suggest that poorer hearing may affect brain regions that are important for different cognitive processes. However, the results should be interpreted with caution as this study is of a cross‐sectional design.

AbstractIntroductionAs hearing loss has been identified as an important risk factor for dementia, we aimed to assess the association between hearing loss and microstructural integrity of the brain.MethodsA total of 1086 dementia‐free participants (mean age = 75.2 [standard deviation: 4.9], 61.4% female) of the population‐based Atherosclerosis Risk in Communities (ARIC) study underwent hearing assessment (2016–2017) and magnetic resonance imaging of the brain (2011–2013). Microstructural integrity was determined with diffusion tensor imaging. Multivariable linear regression was used to investigate associations between hearing loss and microstructural integrity of different brain regions and white matter (WM) tracts.ResultsHearing loss was associated with lower WM microstructural integrity in the temporal lobe, lower gray matter integrity of the hippocampus, and with lower WM microstructural integrity of the limbic tracts and the uncinate fasciculus.ConclusionOur results demonstrate that hearing loss is indepedently associated with lower microstructural integrity in brain regions that are important for different cognitive processes.