Worsening hearing was associated with higher β-amyloid and tau burden in age-related hearing loss

Age-related hearing loss is not linked to cerebrospinal fluid levels of β-amyloid or p-tau181

INTRODUCTION

As Hearing loss and dementia affect people with the same profile, several epidemiological studies have evaluated their relationship. However, the link between age-related hearing loss and Alzheimer's disease is still unclear.

METHODS

We selected subjects with no history of exposure to loud noises, blasts, head trauma with hearing loss, or sudden sensorineural hearing loss from a cohort intended to study preclinical phases of Alzheimer's disease. Participants are volunteers over 55 years without cognitive impairment. We correlated the results of an objective auditory evaluation with brain amyloid and p-tau181 levels and with the outcomes of a comprehensive neuropsychological assessment.

RESULTS

Fifty-five subjects at different stages of the Alzheimer's disease continuum were evaluated. There were no statistically significant correlations between amyloid-β and p-tau levels and any of the objective auditory measures. A weak but significant correlation was found between amyloid-β values and the Hearing Handicap Inventory for the Elderly. The neuropsychological domains more correlated to hearing loss were executive function and processing speed.

DISCUSSION

Age-related hearing loss is not linked to any pathological markers of Alzheimer's disease nor to neuropsychological domains typically affected in this disease. The Hearing Handicap Inventory for the Elderly has an important component of subjectivity and further studies are needed to explore its relationship with amyloid-β levels.

GDF1 ameliorates cognitive impairment induced by hearing loss

Hearing loss is associated with an increased risk of Alzheimer disease (AD). However, the mechanisms of hearing loss promoting the onset of AD are poorly understood. Here we show that hearing loss aggravates cognitive impairment in both wild-type mice and mouse models of AD. Embryonic growth/differentiation factor 1 (GDF1) is downregulated in the hippocampus of deaf mice. Knockdown of GDF1 mimics the detrimental effect of hearing loss on cognition, while overexpression of GDF1 in the hippocampus attenuates the cognitive impairment induced by deafness. Strikingly, overexpression of GDF1 also attenuates cognitive impairment in APP/PS1 transgenic mice. GDF1 activates Akt, which phosphorylates asparagine endopeptidase and inhibits asparagine endopeptidase-induced synaptic degeneration and amyloid-β production. The expression of GDF1 is downregulated by the transcription factor CCAAT-enhancer binding protein-β. These findings indicate that hearing loss could promote AD pathological changes by inhibiting the GDF1 signaling pathway; thus, GDF1 may represent a therapeutic target for AD.

Evaluation of glymphatic system activity by diffusion tensor image analysis along the perivascular space in presbycusis

PURPOSE

Previous studies have suggested that presbycusis (age-related hearing loss) is accompanied with cognitive decline and dementia. However, the neural mechanism underlying the cognitive decline in presbycusis remains unclear. This study aimed to evaluate the glymphatic system function in presbycusis patients compared to healthy controls using diffusion tensor imaging (DTI) with the perivascular space (DTI-ALPS) method.

METHODS

DTI scans were obtained from 30 presbycusis patients with cognitive decline (PCD), 30 presbycusis patients with no cognitive decline (PNCD) and 40 age-, gender-, and education-matched healthy controls (HCs). The DTI-ALPS index was calculated for each group. We evaluated the differences in the DTI-ALPS index among PCD, PNCD and HCs. In addition, we conducted a correlation analysis between the DTI-ALPS index and cognitive performance.

RESULTS

There were significant differences of the DTI-ALPS index among three groups. Post-hoc analysis suggested that the DTI-ALPS index in PCD was significantly lower patients in relative to PNCD and HCs (1.49147 vs. 1.57441 vs. 1.62020, p < 0.001). After correcting for age, gender, and education, the DTI-ALPS index is positively correlated with the MoCA scores (rho = 0.426, p = 0.026).

CONCLUSION

Presbycusis patients with cognitive impairment exhibited decreased glymphatic activity than those without cognitive impairment and HCs. The DTI-ALPS index may provide useful disease progression or treatment biomarkers for patients with presbycusis as an indicator of modulation of glymphatic activity.

Cochlear dysfunction as an early biomarker of cognitive decline in normal hearing and mild hearing loss

INTRODUCTION

Age-related hearing loss is an important risk factor for cognitive decline. However, audiogram thresholds are not good estimators of dementia risk in subjects with normal hearing or mild hearing loss. Here we propose to use distortion product otoacoustic emissions (DPOAEs) as an objective and sensitive tool to estimate the risk of cognitive decline in older adults with normal hearing or mild hearing loss.

METHODS

We assessed neuropsychological, brain magnetic resonance imaging, and auditory analyses on 94 subjects > 64 years of age.

RESULTS

We found that cochlear dysfunction, measured by DPOAEs-and not by conventional audiometry-was associated with Clinical Dementia Rating Sum of Boxes (CDR-SoB) classification and brain atrophy in the group with mild hearing loss (25 to 40 dB) and normal hearing (<25 dB).

DISCUSSION

Our findings suggest that DPOAEs may be a non-invasive tool for detecting neurodegeneration and cognitive decline in the older adults, potentially allowing for early intervention.

Age-related hearing loss associated with differences in the neural correlates of feature binding in visual working memory

The underlying neural mechanisms underpinning the association between age-related hearing loss (ARHL) and dementia remain unclear. A limitation has been the lack of functional neuroimaging studies in ARHL cohorts to help clarify this relationship. In the present study, we investigated the neural correlates of feature binding in visual working memory with ARHL (controls = 14, mild HL = 21, and moderate or greater HL = 23). Participants completed a visual change detection task assessing feature binding while their neural activity was synchronously recorded via high-density electroencephalography. There was no difference in accuracy scores for ARHL groups compared to controls. There was increased electrophysiological activity in those with ARHL, particularly in components indexing the earlier stages of visual cognitive processing. This activity was more pronounced with more severe ARHL and was associated with maintained feature binding. Source space (sLORETA) analyses indicated greater activity in networks modulated by frontoparietal and temporal regions. Our results demonstrate there may be increased involvement of neurocognitive control networks to maintain lower-order neurocognitive processing disrupted by ARHL.

Age-related hearing loss and dementia-related neuropathology: An analysis of the United Kingdom brains for dementia research cohort

Age-related hearing loss frequently precedes or coexists with mild cognitive impairment and dementia. The role specific neuropathologies play in this association, as either a cause or a consequence, is unclear. We therefore aimed to investigate whether specific dementia related neuropathologies were associated with hearing impairment in later life. We analysed data on ante-mortem hearing impairment with post-mortem neuropathological data for 442 participants from the Brains for Dementia Research Cohort. Binary logistic regression models were used to estimate the association of hearing impairment with the presence of each dementia-related neuropathology overall, and with specific staged changes. All analyses adjusted for age and sex, and several sensitivity analyses were conducted to test the robustness of findings. Presence and density of neuritic plaques were associated with higher odds of hearing impairment ante-mortem (OR = 3.65, 95% CI 1.78-7.46 for frequent density of plaques). Presence of any LB disease was likewise associated with hearing impairment (OR = 2.10, 95% CI 1.27-3.48), but this did not increase with higher cortical pathology (OR = 1.53, 95% CI 0.75-3.11). Nonspecific amyloid deposition, neurofibrillary tangle staging, overall AD neuropathology level, and cerebrovascular disease were not clearly associated with increased risks of hearing impairment. Our results provide some support for an association between dementia-related neuropathology and hearing loss and suggest that hearing loss may be associated with a high neuritic plaque burden and more common in Lewy body disease.

Hearing, β-Amyloid Deposition and Cognitive Test Performance in Black and White Older Adults: The ARIC-PET Study

BACKGROUND

Hearing loss is a risk factor for dementia; whether the association is causal or due to a shared pathology is unknown. We estimated the association of brain β-amyloid with hearing, hypothesizing no association. As a positive control, we quantified the association of hearing loss with neurocognitive test performance.

METHODS

Cross-sectional analysis of Atherosclerosis Risk in Communities-Positron Emission Tomography study data. Amyloid was measured using global cortical and temporal lobe standardized uptake value ratios (SUVRs) calculated from florbetapir-positron emission tomography scans. Composite global and domain-specific cognitive scores were created from 10 neurocognitive tests. Hearing was measured using an average of better-ear air conduction thresholds (0.5-4 kHz). Multivariable-adjusted linear regression estimated mean differences in hearing by amyloid and mean differences in cognitive scores by hearing, stratified by race.

RESULTS

In 252 dementia-free adults (72-92 years, 37% Black race, and 61% female participants), cortical or temporal lobe SUVR was not associated with hearing (models adjusted for age, sex, education, and APOE ε4). Each 10 dB HL increase in hearing loss was associated with a 0.134 standard deviation lower mean global cognitive factor score (95% CI: -0.248, -0.019), after adjustment for demographic and cardiovascular factors. Observed hearing-cognition associations were stronger in Black versus White participants.

CONCLUSIONS

Amyloid is not associated with hearing, suggesting that pathways linking hearing and cognition are independent of this pathognomonic Alzheimer's-related brain change. This is the first study to show that the impact of hearing loss on cognition may be stronger in Black versus White adults.

Association of Hearing Loss With Anatomical and Functional Connectivity in Patients With Mild Cognitive Impairment

Importance

Hearing loss is the most important modifiable risk factor for cognitive impairment; however, the association of hearing loss with anatomical and functional connectivity is not fully understood. This association may be elucidated by evaluating the findings of newer imaging technologies.

Objectives

To evaluate the association of hearing loss with anatomical and functional connectivity in patients with mild cognitive impairment (MCI) by using multimodal imaging technology.

Design, Setting, and Participants

This was a prospective cross-sectional study of patients with MCI under the care of a neurology clinic at the Soonchunhyang University Bucheon Hospital (Republic of Korea) from April to September 2021. Data were analyzed from April 1 to June 30, 2022.

Main Outcomes and Measures

Pure tone averages (PTA) and word recognition scores were used to measure hearing acuity. Magnetic resonance imaging (MRI) and positron emission tomography scans of the brain were used to assess functional and anatomical connectivity. Results of diffusion MRI, voxel- and surface-based morphometric imaging, and global brain amyloid standardized uptake ratio were analyzed. Neuroimaging parameters of patients with MCI plus hearing loss were compared with those of patients with MCI and no hearing loss. Correlation analyses among neuroimaging parameters, PTA, and word recognition scores were performed.

Results

Of 48 patients with MCI, 30 (62.5%) had hearing loss (PTA >25 dB) and 18 (37.5%) did not (PTA ≤25 dB). Median (IQR) age was 73.5 (69.0-78.0) years in the group with hearing loss and 75.0 (65.0-78.0) years in the group with normal hearing; there were 20 (66.7%) and 14 (77.8%) women in each group, respectively. The group with MCI plus hearing loss demonstrated decreased functional connectivity between the bilateral insular and anterior divisions of the cingulate cortex, and decreased fractional anisotropy in the bilateral fornix, corpus callosum forceps major and tapetum, left parahippocampal cingulum, and left superior thalamic radiation. Fractional anisotropy in the corpus callosum forceps major and bilateral parahippocampal cingulum negatively correlated with the severity of hearing loss shown by PTA testing. The 2 groups were not significantly different in global β-amyloid uptake, gray matter volume, and cortical thickness.

Conclusion and Relevance

The findings of this prospective cross-sectional study suggest that alterations in the salience network may contribute to the neural basis of cognitive impairment associated with hearing loss in patients who are on the Alzheimer disease continuum.

Distinct disease mechanisms may underlie cognitive decline related to hearing loss in different age groups

BACKGROUND

Hearing loss in older adults is associated with increased dementia risk. Underlying mechanisms that connect hearing loss with dementia remain largely unclear.

METHODS

We studied the association of hearing loss and biomarkers for dementia risk in two age groups with normal cognition: 65 participants from the European Medical Information Framework (EMIF)-Alzheimer's disease (AD) 90+ study (oldest-old; mean age 92.7 years, 56.9% female) and 60 participants from the EMIF-AD PreclinAD study (younger-old; mean age 74.4, 43.3% female). Hearing function was tested by the 'digits-in-noise test' and cognition by repeated neuropsychological evaluation. Regressions and generalised estimating equations were used to test the association of hearing function and PET-derived amyloid burden, and linear mixed models were used to test the association of hearing function and cognitive decline. In the oldest-old group, mediation analyses were performed to study whether cognitive decline is mediated through regional brain atrophy.

RESULTS

In oldest-old individuals, hearing function was not associated with amyloid pathology (p=0.7), whereas in the younger-old individuals hearing loss was associated with higher amyloid burden (p=0.0034). In oldest-old individuals, poorer hearing was associated with a steeper decline in memory, global cognition and language, and in the younger-old with steeper decline in language only. The hippocampus and nucleus accumbens mediated the effects of hearing loss on memory and global cognition in the oldest-old individuals.

CONCLUSIONS

Hearing loss was associated with amyloid binding in younger-old individuals only, and with cognitive decline in both age groups. These results suggest that mechanisms linking hearing loss with risk for dementia depends on age.

Noise-induced auditory damage affects hippocampus causing memory deficits in a model of early age-related hearing loss

Several studies identified noise-induced hearing loss (NIHL) as a risk factor for sensory aging and cognitive decline processes, including neurodegenerative diseases, such as dementia and age-related hearing loss (ARHL). Although the association between noise- and age-induced hearing impairment has been widely documented by epidemiological and experimental studies, the molecular mechanisms underlying this association are not fully understood as it is not known how these risk factors (aging and noise) can interact, affecting memory processes. We recently found that early noise exposure in an established animal model of ARHL (C57BL/6 mice) accelerates the onset of age-related cochlear dysfunctions. Here, we extended our previous data by investigating what happens in central brain structures (auditory cortex and hippocampus), to assess the relationship between hearing and memory impairment and the possible combined effect of noise and sensory aging on the cognitive domain. To this aim, we exposed juvenile C57BL/6 mice of 2 months of age to repeated noise sessions (60 min/day, pure tone of 100 dB SPL, 10 kHz, 10 consecutive days) and we monitored auditory threshold by measuring auditory brainstem responses (ABR), spatial working memory, by using the Y-maze test, and basal synaptic transmission by using ex vivo electrophysiological recordings, at different time points (1, 4 and 7 months after the onset of noise exposure, corresponding to 3, 6 and 9 months of age). We found that hearing loss, along with accelerated presbycusis onset, can induce persistent synaptic alterations in the auditory cortex. This was associated with decreased memory performance and oxidative-inflammatory injury in the hippocampus, the extra-auditory structure involved in memory processes. Collectively, our data confirm the critical relationship between auditory and memory circuits, suggesting that the combined detrimental effect of noise and sensory aging on hearing function can be considered a high-risk factor for both sensory and cognitive degenerative processes, given that early noise exposure accelerates presbycusis phenotype and induces hippocampal-dependent memory dysfunctions.