Smaller Hippocampal Volume and Degraded Peripheral Hearing Among Japanese Community Dwellers

Abstract

A growing body of literature has demonstrated that dementia and hearing loss are interrelated. Recent interest in dementia research has expanded to brain imaging analyses with auditory function. The aim of this study was to investigate the link between hearing ability, which was assessed using pure-tone audiometry, and the volume of brain regions, specifically the hippocampus, entorhinal cortex, Heschl’s gyrus, and total gray matter, using Freesurfer software and T1-weighted brain magnetic resonance imaging. The data for 2082 samples (age range = 40–89 years) were extracted from a population-based cohort of community dwellers. Hearing-impaired individuals showed significantly smaller hippocampal volumes compared with their non-hearing-impaired counterparts for all auditory frequency ranges. In addition, a correlational analysis showed a significant dose-response relationship for hearing ability and hippocampal volume after adjusting for potential confounding factors so that the more degraded the peripheral hearing was, the smaller the hippocampal volume was. This association was consistent through the auditory frequency range. The volume of the entorhinal cortex, right Heschl’s gyrus and total gray matter did not correlate with hearing level at any frequency. The volume of the left Heschl’s gyrus showed a significant relationship with the hearing levels for some auditory frequencies. The current results suggested that the presence of hearing loss after middle age could be a modifier of hippocampal atrophy.

Dietary diversity is associated with longitudinal changes in hippocampal volume among Japanese community dwellers

“…net) [20] was used for the cortical surface reconstructions and regional grey matter volume estimations. The technical details of these procedures have been described previously [7]. In short, the fully automated procedure in FreeSurfer involved preprocessing the subject's image data, segmenting the cortical grey matter and white matter (GM/WM), tessellating the GM/WM junction, inflating the folded surface tessellation patterns, and automatically correcting the topologic defects.…”

“…We previously hypothesised that multiple nutritional deficiencies caused by an unbalanced diet might be a risk factor for cognitive decline and found that higher dietary diversity was associated with better cognitive function among older Japanese subjects [6]. However, we defined cognitive decline using the Mini-Mental State Examination [7]. A more objective measurement without the retest effect is needed to assess brain function.…”

“…In this study, we focused on structural neuroimaging analyses to explore brain regions associated with dietary factors. The hippocampus is a key structure in memory processing, the disturbance of which is a core symptom of dementia, and hippocampal atrophy occurs in AD and non-AD dementia disorders [7,8]. Previous investigations have reported that greater adherence to the Mediterranean diet was associated with a larger hippocampal volume among 674 multiethnic older adults [9], a Western diet was associated with a smaller hippocampal volume after 4 years of follow-up among 255 older Australian subjects [10], and the long-term Healthy Eating Score was positively associated with hippocampal volume at the end of follow-up among 459 Whitehall II sub-study participants [11].…”

Hearing loss is associated with gray matter differences in older adults at risk for and with Alzheimer’s disease

“…In other words, the right hippocampus of these individuals with moderate to severe hearing loss "looks" approximately 8 years older given that the normal shrinkage is approximately 0.5% annually for people above 60 years of age (Fjell et al, 2009). Previous cross-sectional research has found similar associations between pure-tone hearing loss and hippocampal volume in healthy older adults (Uchida et al, 2018). There have been similar findings in longitudinal studies showing accelerated decline in the hippocampus (Xu et al, 2019) and in the right parahippocampus across time in healthy older adults with pure-tone hearing loss.…”

Interacting effects of frontal lobe neuroanatomy and working memory capacity to older listeners’ speech recognition in noise

“…Also cross-sectional work has shown that pure-tone hearing loss is related to neuroanatomical alterations of gray matter volume and thickness (Alfandari et al, 2018;Eckert et al, 2012;Rigters et al, 2018Rigters et al, , 2017Tuwaig et al, 2017;Rudner et al, 2019;Uchida et al, 2018;Ren et al, 2018;Armstrong et al, 2019;Neuschwander et al, 2019;Giroud et al, in prep., but see Profant et al, 2014).…”