Hearing Loss and Neuroimaging Characteristics

Introduction: Hearing loss has been implicated as an important modifiable risk factor for dementia. Prior research using pure-tone averages (PTAs) has suggested a neuroanatomical link between adult hearing loss and temporal lobe volume loss. The primary aim of the current work was to investigate the association between formal pure-tone and speech audiometry with neuroimaging characteristics reflective of aging and dementia in older adults.

Methods: This prospective population-based study included participants from the Mayo Clinic Study of Aging, ≥60 years old, with normal cognition or mild cognitive impairment, baseline neuroimaging, and an audiogram associated with the neuroimaging. Imaging modalities included structural magnetic resonance imaging (sMRI; N=605), diffusion tensor imaging (DTI-MRI; N=444), and fluorodeoxyglucose (FDG)-positron emission tomography (PET; N=413). Multivariable logistic and linear regression models were used to evaluate associations with neuroimaging outcomes.

Results: Mean (SD) PTA was 33 (15) dB HL and mean (SD) word recognition score (WRS) was 91% (14%). From sMRI, each 10% increase in PTA was associated with increased likelihood of abnormal white-matter hyperintensity (odds ratio 1.26, 95% CI 1.04 to 1.54, p=0.02). From DTI-MRI, participants with < 100% WRSs had significantly lower fractional anisotropy (FA) in the corpus callosum, particularly in the genu (parameter estimate [PE] -0.012, 95% CI -0.021 to -0.003, p=0.008) compared to those with perfect WRSs. From FDG-PET, each 10% decrease in WRSs was associated with decreased uptake in the anterior cingulate cortex (PE -0.013, 95% CI -0.021 to -0.005, p=0.001).

Conclusions: Poorer audiometric markers were associated with increased abnormal white-matter hyperintensities and decreased FA of the corpus callosum, which are early markers of cerebrovascular disease, suggesting a vascular pathophysiologic link between these findings. Further studies are needed to examine the dynamic neuroplasticity that likely occurs in the setting of chronic hearing loss.