Central auditory dysfunction may precede the onset of clinical dementia in people with probable Alzheimer's disease

Late-onset depression is associated to age-related central auditory processing disorder in an older population in Southern Italy

The association between late-life depression (LLD) and age-related hearing loss (ARHL) was suggested by preliminary studies, but reliance on LLD subtypes may introduce significant bias. We examined the association between ARHL and LLD according to the age of onset (early-onset depression (EOD) and late-onset depression (LOD)). We investigated the association between ARHL and LLD diagnosed according to the Semi-structured Clinical Diagnostic Interview for DSM-IV-TR in 1749 Italian community-dwelling older subjects from the population-based GreatAGE Study, Southern Italy. Peripheral ARHL was assessed as a pure tone average (PTA) threshold > 40 dB hearing level in the better ear- and age-related CAPD as a score of < 50% to the Synthetic Sentences Identification with Ipsilateral Competitive Message (SSI-ICM) test. LLD amounted at 10.29% of the sample, subdivided in LOD (6.21%) and EOD (4.08%). Age-related CAPD tended to be higher in LOD (28.91%) than in EOD (19.05%). After accounting for covariates, LOD was tendentially associated to age-related CAPD, but not to peripheral ARHL. This trend was confirmed by the linear models in which LOD was significantly associated to worsen SSI-ICM percentages (odds ratio 2.38, 95% confidence interval 1.32-4.30, p = 0.004), but not to PTA values. In a fully adjusted model of LOD, the effect of the association between CAPD and LOD was explained by social dysfunction. LLD was not associated to peripheral ARHL. Age-related CAPD was associated to LOD, a form of depression with cognitive dysfunction hallmark. The ARHL assessment may be an important opportunity to prevent depressive disorders in later life, particularly for LOD.

Association of genetic risk for Alzheimer disease and hearing impairment

OBJECTIVE

To test the hypothesis that incipient Alzheimer disease (AD) may adversely affect hearing and that hearing loss may adversely affect cognition, we evaluated whether genetic variants that increase AD risk also increase problem hearing and genetic variants that increase hearing impairment risk do not influence cognition.

METHODS

UK Biobank participants without dementia ≥56 years of age with Caucasian genetic ancestry completed a Digit Triplets Test of speech-in-noise hearing (n = 80,074), self-reported problem hearing and hearing with background noise (n = 244,915), and completed brief cognitive assessments. A genetic risk score for AD (AD-GRS) was calculated as a weighted sum of 23 previously identified AD-related polymorphisms. A genetic risk score for hearing (hearing-GRS) was calculated using 3 previously identified polymorphisms related to hearing impairment. Using age-, sex-, and genetic ancestry-adjusted logistic and linear regression models, we evaluated whether the AD-GRS predicted poor hearing and whether the hearing-GRS predicted worse cognition.

RESULTS

Poor speech-in-noise hearing (>-5.5-dB speech reception threshold; prevalence 14%) was associated with lower cognitive scores (ß = -1.28; 95% confidence interval [CI] -1.54 to -1.03). Higher AD-GRS was significantly associated with poor speech-in-noise hearing (odds ratio [OR] 1.06; 95% CI 1.01-1.11) and self-reported problems hearing with background noise (OR 1.03; 95% CI 1.00-1.05). Hearing-GRS was not significantly associated with cognitive scores (ß = -0.05; 95% CI -0.17 to 0.07).

CONCLUSIONS

Genetic risk for AD also influences speech-in-noise hearing. We failed to find evidence that genetic risk for hearing impairment affects cognition. AD disease processes or a that shared etiology may cause speech-in-noise difficulty before dementia onset.

The Peripheral Hearing and Central Auditory Processing Skills of Individuals With Subjective Memory Complaints

Purpose

This study examined the central auditory processing (CAP) assessment results of adults between 45 and 85 years of age with probable pre-clinical Alzheimer’s disease – i.e., individuals with subjective memory complaints (SMCs) as compared to those who were not reporting significant levels of memory complaints (non-SMCs). It was hypothesized that the SMC group would perform significantly poorer on tests of central auditory skills compared to participants with non-SMCs (control group).

Methods

A total of 95 participants were recruited from the larger Western Australia Memory Study and were classified as SMCs (N = 61; 20 males and 41 females, mean age 71.47 ±7.18 years) and non-SMCs (N = 34; 10 males, 24 females, mean age 68.85 ±7.69 years). All participants completed a peripheral hearing assessment, a CAP assessment battery including Dichotic Digits, Duration Pattern Test, Dichotic Sentence Identification, Synthetic Sentence Identification with Ipsilateral Competing Message (SSI-ICM) and the Quick-Speech-in-Noise, and a cognitive screening assessment.

Results

The SMCs group performed significantly poorer than the control group on SSI-ICM −10 and −20 dB signal-to-noise conditions. No significant differences were found between the two groups on the peripheral hearing threshold measurements and other CAP assessments.

Conclusions

The results suggest that individuals with SMCs perform poorly on specific CAP assessments in comparison to the controls. The poor CAP in SMC individuals may result in a higher cost to their finite pool of cognitive resources. The CAP results provide yet another biomarker that supports the hypothesis that SMCs may be a primary indication of neuropathological changes in the brain. Longitudinal follow up of individuals with SMCs, and decreased CAP abilities should inform whether this group is at higher risk of developing dementia as compared to non-SMCs and those SMC individuals without CAP difficulties.

Macular Ganglion Cell-Inner Plexiform Layer as a Marker of Cognitive and Sensory Function in Midlife

BACKGROUND

Neurodegenerative diseases are public health challenges in aging populations. Early identification of people at risk for neurodegeneration might improve targeted treatment. Noninvasive, inexpensive screening tools are lacking but are of great potential. Optical coherence tomography (OCT) measures the thickness of nerve cell layers in the retina, which is an anatomical extension of the brain and might be indicative of common underlying neurodegeneration. We aimed to determine the association of macular ganglion cell-inner plexiform layer (mGCIPL) thickness with cognitive and sensorineural function in midlife.

METHOD

This cross-sectional study included 1,880 Beaver Dam Offspring Study participants (aged 27-93 years, mean 58) who participated in the 10-year follow-up examination. We assessed cognitive function and impairment, hearing sensitivity thresholds and impairment, central auditory processing, visual impairment, and olfactory impairment. We measured mGCIPL using the Cirrus 5000 HD-OCT Macular Cube Scan. Multivariable linear and logistic regression models adjusted for potential confounders were used to determine associations between mGCIPL thickness and cognitive and sensorineural functions, as well as for comparing participants with a thin mGCIPL (1 SD below average) to the remainder in those functions.

RESULTS

Thinner mGCIPL was associated with worse cognitive function, worse central auditory function, and visual impairment. We found an association of mGCIPL thickness with hearing sensitivity in women only and no association with impairment in hearing, olfaction, and cognition. Results on the thin group comparisons were consistent.

CONCLUSIONS

mGCIPL thickness is associated with cognitive and sensorineural function and has the potential as a marker for neurodegeneration in middle-aged adults.

Left Ear Hearing Predicts Functional Activity in the Brains of Patients with Alzheimer's Disease Dementia

OBJECTIVES

To determine whether central speech processing ability, as measured by hearing in noise, differs between right and left ears in adults with Alzheimer's disease related dementia (AD) as well as whether differences in central speech processing ability correlate with an fMRI-based measurement of global functional brain connectivity.

METHODS

This prospective study was carried out at a tertiary referral center. Patients with an AD diagnosis and pure tone averages 40 dB HL or better were included. They were examined using resting-state fMRI and underwent central audiometric testing using the Dichotic Sentence Identification Test (DSI), the Dichotic Digits Test (DD), and the Synthetic Sentence Identification Test (SS), which test hearing in noise. DSI scores were correlated with resting-state fMRI connectivity between 361 distinct gray matter brain regions of interest (ROIs). Average global connectivity was calculated as mean functional connectivity between an ROI and the other 360 regions, a quantitative marker representing overall functional connectivity in the brain.

RESULTS

Sixteen subjects had adequate fMRI and hearing data. The average age was 71.5 years old (±6.0). The average DSI score for the left ear was 40% (±34%) compared to 90% (±10%) in the right ear (P < .001). No difference between ears was noted on the DD. SS does not differentiate between ears, but worsening scores were noted with increasing background noise. Of the fMRI ROIs, 269 of the 361 had multiple comparison corrected significant correlations between global connectivity and DSI of the left ear (P = .004, r = .673), and all 269 showed higher functional connectivity for individuals with higher left DSI score. No correlations between DSI of the right ear and functional connectivity were found.

CONCLUSIONS

Correlation was noted between left sided DSI and functional connectivity in patients with AD. Auditory input from the left ear was more susceptible to impairment, suggesting that side-specific auditory input may influence central auditory processing.

Are auditory processing and cognitive performance assessments overlapping or distinct? Parsing the auditory behaviour of older adults

OBJECTIVE

Auditory processing predicts cognitive decline, including dementia, in older adults. Auditory processing involves the understanding, interpretation, and communication of auditory information. Cognition is linked to auditory processing; however, it is disputed whether auditory processing is a separate construct distinct from cognition. The purpose of this study was to determine if auditory processing is distinct from cognition in older adults.

DESIGN

Participants completed 14 cognitive and auditory processing assessments. Assessments were subjected to exploratory factor analysis with principal components extraction and varimax rotation with Kaiser normalisation. Study sample: 213 community-dwelling older adults (M = 71.39 years, 57% female, 93% Caucasian, M = 16 years education) with and without mild cognitive impairment (MCI) participated.

RESULTS

Four factors were identified, explaining 66.3% of the total variance: (1) executive functions, visual processing speed, and dichotic auditory processing, (2) auditory processing of degraded speech, (3) memory, and (4) auditory temporal processing of nonspeech.

CONCLUSIONS

Two domains of auditory processing (processing degraded speech and temporal processing) account for unique variance to which cognitive measures are not sensitive, while measures of auditory dichotic processing appear to be tapping similar abilities as measures of cognition. Older adults who perform poorly on dichotic measures should be screened for cognitive impairment.

Systematic review protocol for assessing central auditory functions of Alzheimer's disease and its preclinical stages

INTRODUCTION

A number of studies have reported an association between peripheral hearing impairment, central auditory processing and Alzheimer's disease (AD) and its preclinical stages. Both peripheral hearing impairment and central auditory processing disorders are observed many years prior to the clinical manifestation of AD symptoms, hence, providing a long window of opportunity to investigate potential interventions against neurodegenerative processes. This paper outlines the protocol for a systematic review of studies examining the central auditory processing functions in AD and its preclinical stages, investigated through behavioural (clinical assessments that require active participation) central auditory processing tests.

METHODS AND ANALYSIS

We will use the keywords and Medical Subject Heading terms to search the following electronic databases: MEDLINE, PsychINFO, PubMed, Scopus, EMBASE and CINAHL Plus. Studies including assessments of central auditory function in adults diagnosed with dementia, AD and its preclinical stages that were published before 8 May 2019 will be reviewed. This review protocol will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols guidelines. Data analysis and search results will be reported in the full review. This manuscript has designed the protocols for a systematic review that will identify the behavioural clinical central auditory processing measures that are sensitive to the changes in auditory function in adults with AD and its preclinical stages. Such assessments may subsequently help to design studies to examine the potential impact of hearing and communication rehabilitation of individuals at risk of AD.

ETHICS AND DISSEMINATION

Ethical approval is not required as this manuscript only reports the protocols for conducting a systematic review as primary data will only be reviewed and not be collected. The results of this systematic review will be disseminated through publication and in scientific conferences.

PROSPERO REGISTRATION NUMBER

CRD42017078272.

5XFAD mice show early-onset gap encoding deficits in the auditory cortex

Early detection will be crucial for effective treatment or prevention of Alzheimer's disease. The identification and validation of early, noninvasive biomarkers is therefore key to avoiding the most devastating aspects of Alzheimer's disease. Measures of central auditory processing such as gap detection have recently emerged as potential biomarkers in both human patients and the 5XFAD mouse model of Alzheimer's disease. Full validation of gap detection deficits as a biomarker will require detailed understanding of the underlying neuropathology, including which brain structures are involved and how the operation of neural circuits is affected. Here we show that 5XFAD mice exhibit gap detection deficits as early as 2 months of age, well before development of Alzheimer's disease-associated pathology. We then examined responses of neurons in the auditory cortex to gaps in white noise. Both gap responses and baseline firing rates were robustly and progressively degraded in 5XFAD mice compared to littermate controls. These impairments were first evident at 2-4 months of age in males, and 4-6 months in females. This demonstrates early-onset impairments to the central auditory system, which could be due to damage in the auditory cortex, upstream subcortical structures, or both.

Prognostic Value of a Test of Central Auditory Function in Conversion from Mild Cognitive Impairment to Dementia

BACKGROUND/OBJECTIVE

It has been suggested that central auditory processing dysfunction might precede the development of cognitive decline and Alzheimer's disease (AD). The Dichotic Digits Test (DDT) has been proposed as a test of central auditory function. Our objective was to evaluate the predictive capacity of the DDT in conversion from mild cognitive impairment (MCI) to dementia.

METHODS

A total of 57 participants (26 females) with MCI were tested at baseline with pure tone audiometry, speech in quiet and in noise, and the DDT. The cognitive outcome was retrieved from medical files after 5 years. Groupwise comparisons of the baseline DDT scores were performed and the relative risk was calculated.

RESULTS

Altogether 22 subjects developed any kind of dementia. Of the original 57 individuals within the MCI group, 15 developed AD and 7 developed other types of dementia. There was no significant difference in baseline DDT scores between the participants who converted to AD and those who did not. However, the group who developed other types of dementia (especially frontotemporal dementia) had lower DDT scores in the left ear than those participants who did not develop dementia. With a baseline DDT score below 50% correct responses, the participants diagnosed with MCI had a 2.49-times-higher risk of developing dementia than those with scores of 50% or better.

CONCLUSION

The DDT as a central auditory test may be suitable when evaluating cognitive decline.

Age-Related Central Auditory Processing Disorder, MCI, and Dementia in an Older Population of Southern Italy

OBJECTIVE

We explored the associations of age-related central auditory processing disorder (CAPD) with mild cognitive impairment (MCI) and dementia in an older population-based cohort in Apulia, Southern Italy (GreatAGE Study).

STUDY DESIGN

Cross-sectional data from a population-based study.

SETTING

Castellana Grotte, Bari, Italy.

SUBJECTS AND METHODS

Between 2013 and 2018, MCI, dementia, age-related CAPD (no disabling hearing loss and <50% score on the SSI-ICM test [Synthetic Sentence Identification-Ipsilateral Competing Message]), neurologic and neuropsychological examinations, and serum metabolic biomarkers assays were investigated on 1647 healthy volunteers aged >65 years.

RESULTS

The prevalences of age-related CAPD, MCI, and dementia were 14.15%, 15.79%, and 3.58%, respectively. Among the subjects with MCI and dementia, 19.61% and 42.37% had age-related CAPD. In the regressive models, age-related CAPD was associated with MCI (odds ratio, 1.50; 95% CI, 1.01-2.21) and dementia (odds ratio, 2.23; 95% CI, 1.12-4.42). Global cognition scores were positively associated with increasing SSI-ICM scores in linear models. All models were adjusted for demographics and metabolic serum biomarkers.

CONCLUSION

The tight association of age-related CAPD with MCI and dementia suggests the involvement of central auditory pathways in neurodegeneration, but it is not clear which is the real direction of this association. However, CAPD is a possible diagnostic marker of cognitive dysfunction in older patients.

Does Treating Hearing Loss in Older Adults Improve Cognitive Outcomes? A Review

Hearing loss is the third most prevalent health condition in older age. In recent years, research has consistently reported an association between hearing loss and mental health outcomes, including poorer cognitive performances. Whether treating hearing loss in elders improves cognition has been directly or indirectly addressed by several studies. This review aims at providing a synthesis of those results. Regarding the literature on hearing aids’ use and cognition, although the lack of interventional studies has to be underlined, observational data suggest that hearing aids positively impact long-term cognition, even though more research is necessary to ascertain this statement and provide information on the length or frequency of use required in order to observe benefits. Regarding cochlear implants in elders experiencing more severe auditory deprivation, the literature is scarcer. The available studies have many limitations and do not allow the drawing of clear conclusions. Taken together, the results are encouraging. Nevertheless, because hearing loss is suspected to account for 9% of dementia cases, and also because hearing loss is one of the few potentially modifiable factors from a dementia prevention perspective, the need to stimulate research to have clearer knowledge of the benefits of treating hearing loss on cognitive outcomes is urgent.

Hearing handicap in Asian patients with dementia

BACKGROUND

Hearing loss and hearing handicap may contribute to cognitive impairment and dementia. The purpose of this study was to analyze the association between hearing loss and hearing handicap with dementia in an Asian memory clinic parents.

METHODS

This study includes the data obtained from patients with mild dementia who attended the National University hospital memory clinic and non-demented healthy subjects among spouses and caregivers who are non-genetically related to our patients. All participants underwent comprehensive physical, medical, neuropsychological and audiological assessments (i.e. pure tone audiometry - PTA). Disabling hearing loss was defined as a hearing loss of >40 dB in the better ear on PTA. Amsterdam Inventory for Auditory Disability and Handicap (AIADH) questionnaire was administered through the verbal interview to measure their hearing handicap score. Linear regression models were used to investigate the association between hearing loss and hearing handicap with dementia. Mean differences (β) with 95% confidence intervals (CI) were calculated.

RESULTS

91 participants (65-90 years old) were recruited for this study; 39 of them were patients with dementia and 52 were non-demented healthy controls. 48.7% of the patients with dementia had disabling hearing loss, which is higher than the non-demented controls (25.0%) (p = 0.019). The significant association between hearing handicap (as measured by AIADH) and dementia was observed, which was independent of demographic factors and audiology related history and PTA average (β = -6.40; 95% CI =0.11.99, -0.81, p = 0.025). There was no independent association between hearing loss and dementia (p > 0.05).

CONCLUSION

A significant association between hearing handicap and dementia was found. The mechanism of this association requires further research and may involve higher order central processing disorder.

Audiometric Age-Related Hearing Loss and Cognition in the Hispanic Community Health Study

BACKGROUND

Age-related hearing loss (HL), a common and treatable condition, has been associated with other age-related conditions. Late life cognitive impairment is a major public health concern that is rarely treatable. Studies examining the relationship between HL and cognition have been limited by non-Hispanic cohorts, small samples, or limited confounding control. We overcome these limitations in a large Hispanic cohort.

METHODS

This was a multisite cross-sectional study of 5,277 subjects at least 50 years old (Hispanic Community Health Study, HCHS). The main exposure was audiometric HL. The main outcome measure was neurocognitive performance ascertained by the Digit Symbol Substitution Test (DSST), Word Frequency Test, Spanish-English Verbal Learning Test (SEVLT), and Six-Item Screener.

RESULTS

The mean age was 58.4 years (SD = 6.2). A 20-dB (equivalent to a one-category worsening) increase in HL was associated with a -1.53 (95% CI, -2.11, -0.94) raw score point difference in the DSST, adjusting for demographics, hearing aid use, and cardiovascular disease. Similarly, a 20-dB increase in HL was associated with a -0.86 (-1.23, -0.49) point difference on the Word Frequency Test, -0.76 (-1.04, -0.47) on the SEVLT 3 trials, -0.45 (-0.60, -0.29) on the SELVT recall, and -0.07 (-0.12, -0.02) on the Six-Item Screener.

CONCLUSIONS

In the largest study of formal, audiometric HL and cognition to date, HL was independently associated with worse performance in a range of neurocognitive measures. Because HL is common and potentially treatable, it should be investigated as a modifiable risk factor for neurocognitive decline and dementia.

Hearing loss is an early biomarker in APP/PS1 Alzheimer's disease mice

Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive loss of memory and cognitive decline. Over the last decade, it has been found that defects in sensory systems could be highly associated with AD. Hearing is an important neural sense. However, little is known about hearing functional changes in AD. In this study, APP/PS1 AD mice (Jackson Lab: Stack No. 004462) were used. Hearing function was assessed by auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), and cochlear microphonics (CM) recordings. Wild-type (WT) littermates served as control. We found that APP/PS1 AD mice measured as ABR threshold had hearing loss. The hearing loss appeared at high frequency as early as 2 months old, prior to the reported occurrence of spatial learning deficit at 6-7 months of age in this AD mouse model. The hearing loss was progressive and extended from high frequency to low frequency. At 3-4 months old, the hearing loss appeared in the whole-frequency range. Moreover, the wave IV and V in the super-threshold ABR were eliminated, indicating substantial impairment in inferior colliculus, nuclei of lateral lemniscus, and medial geniculate body in the upper brainstem. DPOAE in APP/PS1 AD mice was also reduced. However, there was no reduction in CM in APP/PS1 mice. These data demonstrate that unlike age-related hearing loss APP/PS1 AD mice have early onset of hearing loss. These data also suggest that hearing function testing could provide a simple, sensitive, non-invasive screen-tool for early detecting AD and localizing lesion.

Multisensory, Multi-Tasking Performance of Older Adults With and Without Subjective Cognitive Decline

As the population ages, it is increasingly important to detect non-normative cognitive declines as early as possible. Measures of combined sensory–motor–cognitive functioning may be early markers for identifying individuals who are at increased risk of developing dementia. Further, older adults experiencing subjective cognitive decline (SCD) may have elevated risk of dementia compared to those without SCD. Tasks involving complex, multisensory interactions reflective of everyday challenges may be particularly sensitive to subjectively perceived, pre-clinical declines. In the current study, older adults with and without SCD were asked to simultaneously perform a standing balance task and a listening task under increasingly challenging sensory/cognitive/motor conditions using a dual-task paradigm in a realistic, immersive virtual environment. It was hypothesized that, compared to older adults without SCD, those with SCD would exhibit greater decrements in postural control and listening response accuracy as sensory/motor/cognitive loads increased. However, counter to predictions, older adults with SCD demonstrated greater reductions in postural sway under more challenging dual-task conditions than those without SCD. Across both groups, poorer postural task performance was associated with poorer cognitive function and speech-in-noise thresholds measured with standard baseline tests. Poorer listening task performance was associated with poorer global cognitive function, poorer mobility, and poorer speech-in-noise detection. Overall, the results provide additional support for the growing evidence demonstrating associations between sensory, motor, and cognitive functioning and contribute to an evolving consideration of how best to categorize and characterize SCD in a way that guides strategies for screening, assessment, and intervention.

Age-related hearing loss and tinnitus, dementia risk, and auditory amplification outcomes

Age-related hearing loss (ARHL) or presbycusis, as the third leading cause of chronic disability in older adults, has been shown to be associated with predisposing cognitive impairment and dementia. Tinnitus is also a chronic auditory disorder demonstrating a growth rate with increasing age. Recent evidence stands for the link between bothersome tinnitus and impairments in various aspects of cognitive function. Both ARHL and age-related tinnitus affect mental health and contribute to developing anxiety, stress, and depression. The present review is a comprehensive multidisciplinary study on diverse interactions among ARHL, tinnitus, and cognitive decline in older adults. This review incorporates the latest evidence in prevalence and risk factors of ARHL and tinnitus, the neural substrates of tinnitus-related cognitive impairments, hypothesized mechanisms concerning the association between ARHL and increased risk of dementia, hearing amplification outcomes in cases with ARHL and cognitive decline, and preliminary findings on the link between ARHL and cognitive impairment in animal studies. Given extensive evidence that demonstrates advantages of using auditory amplification in the alleviation of hearing handicap, depression, and tinnitus, and the improvement of cognition, social communication, and quality of life, regular hearing screening programs for identification and management of midlife hearing loss and tinnitus is strongly recommended.

Informant-based hearing difficulties and the risk for mild cognitive impairment and dementia

BACKGROUND

hearing loss has been associated with mild cognitive impairment (MCI) and dementia. Studies have not assessed whether hearing difficulties (HD) that interfere with daily activities as reported by partners can be a marker for increased risk for cognitive decline and impairment.

OBJECTIVE

to assess the cross-sectional and longitudinal associations between informant-based HD, which interfere with daily activities and the risk for MCI and dementia.

METHODS

the study included 4812 participants without dementia, enrolled in the Mayo Clinic Study of Aging (mean age (SD) 73.7 (9.6) years) with cognitive evaluation and informant-based report on participant's HD that interfere significantly with daily activities at baseline and for every 15 months. Cox proportional hazards models (utilising time-dependent HD status and age as the time scale) were used to examine HD and the risk for MCI or dementia, and mixed-effects models (allowing for random subject-specific intercepts and slopes) were used to examine the relationship between HD and cognitive decline.

RESULTS

about, 981 participants had HD and 612 (12.7%) had prevalent MCI at baseline; 759 participants developed incident MCI and 273 developed incident dementia. In cognitively unimpaired participants at baseline, those with HD had higher risk for MCI (hazard ratio [HR] = 1.29, 95% confidence interval [CI] (1.10, 1.51), P = 0.002; adjusting for sex, years of education). In participants without dementia, those with HD had higher risk for dementia (HR: 1.39, 95% CI, (1.08-1.79), P = 0.011; adjusting sex and education). In individuals with MCI, HD was associated with modestly greater cognitive decline.

CONCLUSIONS

informant-based HD was associated with increased risk for MCI and dementia.

Prospective Evaluation of Cognitive Functions After Rehabilitation With Cochlear Implant or Hearing Aids: Preliminary Results of a Multicentric Study on Elderly Patients

Objective Recent literature has shown a growing interest in the relationship between presbycusis and cognitive decline, but significant evidence about the long-term benefit of rehabilitation on cognitive functions has not been reported yet. The aim of the study was to analyze audiological and neuropsychological performances in patients with cochlear implant (CI) or hearing aids (HAs) over time. Materials and Method Forty-four bilaterally deaf patients aged more than 60 years (25 with CI candidacy and 19 with HA candidacy) were enrolled. Patients were subjected to audiological evaluation, to a battery of neuropsychological tests (Mini-Mental State Examination [MMSE], Rey Auditory Verbal Learning Task [RAVLT], Rey-Osterreith Complex Figure Test, Digit/Corsi Span Forward and Backward, Multiple Features Target Cancellation, Trail-Making Test, Stroop Test, and Phonological and Semantic Word Fluency), and to a quality of life assessment (Short Form 36, Glasgow Benefit Inventory, Glasgow Health Status Inventory) at the baseline and after a long-term follow-up (6-12 months). Results Speech recognition scores in quiet and in noise were significantly improved even 6 months after auditory rehabilitation. Significant differences between pre- and post-rehabilitation scores were reported in physical and emotional impacts in life, general global health, vitality, and social activities. MMSE and RAVLT scores were significantly improved in both groups after 6 months of follow-up, suggesting a global involvement of memory domain. Mnesic performances remained unchanged between the first and second follow-up, but a further significant improvement in executive functions (Stroop Test) was detected in patients with CI reevaluated 12 months after implantation. A significant correlation of the RAVLT with signal-to-noise ratio at +10 dB speech-in-noise scores and the MMSE with signal-to-noise ratio at 0 dB speech-in-noise scores suggests the pivotal role of executive functions in recognition in noisy environment. Conclusions Our preliminary data confirm that hearing deprivation in aged patients represents a truly modifiable risk factor for cognitive decline, which can be positively faced by acoustic rehabilitation. The improvement of short- and long-term memory performances and the amelioration of executive and attentive functions suggest that hearing restoration with both HAs and CI may provide a recovery of superior cognitive domains probably through a reallocation of cortical resources altered by hearing deprivation.

Effect of Hearing Ability and Mild Behavioural Impairment on MoCA and Memory Index Scores

BACKGROUND

The life-course model of modifiable risk factors for dementia now recognizes managing hearing loss and addressing social isolation.

OBJECTIVE

To investigate the contribution and inter-relationship of hearing ability and behaviour change on cognitive ability.

METHODS

We present the preliminary findings from a prospective longitudinal study of 35 non-demented participants ages 60-93, recruited from community rehabilitation and acute-care programs of Geriatric Medicine, who underwent baseline hearing, behavioural, and cognitive testing.

RESULTS

After controlling for age and hearing impairment, the left ear Dichotic Digit Test (DDT) score accounted uniquely for 20% of the variance in MoCA Memory Index (p = .016 with β = .598). Mild Behavioural Impairment (MBI) was highly prevalent, with 80% of older adults reporting at least one MBI symptom. People with hearing impairment had greater global MBI burden than people with normal hearing, especially in the domains of apathy and impulse dyscontrol; however, greater severity of hearing impairment was not associated with a higher number of neuropsychiatric symptoms (NPS).

CONCLUSIONS

Low left DDT contributed to lower memory index and greater MBI burden is associated with hearing impairment. Our findings demonstrate the value of early non-invasive hearing and behavioural assessments as part of dementia risk assessment in older adults.

Keys to staying sharp: A randomized clinical trial of piano training among older adults with and without mild cognitive impairment

BACKGROUND

The prevalence of dementia, the most expensive medical condition (Kirschstein, 2000 and Hurd et al., 2013 [1,2]), and its precursor, mild cognitive impairment (MCI) are increasing [3]. Finding effective intervention strategies to prevent or delay dementia is imperative to public health. Prior research provides compelling evidence that central auditory processing (CAP) deficits are a risk factor for dementia [4-6]. Grounded in the information degradation theory [7, 8], we hypothesize that improving brain function at early perceptual levels (i.e., CAP) may be optimal to attenuate cognitive and functional decline and potentially curb dementia prevalence. Piano training is one avenue to enhance cognition [9-13] by facilitating CAP at initial perceptual stages [14-18].

OBJECTIVES

The Keys To Staying Sharp study is a two arm, randomized clinical trial examining the efficacy of piano training relative to music listening instruction to improve CAP, cognition, and everyday function among older adults. In addition, the moderating effects of MCI status on piano training efficacy will be examined and potential mediators of intervention effects will be explored.

HYPOTHESES

We hypothesize that piano training will improve CAP and cognitive performance, leading to functional improvements. We expect that enhanced CAP will mediate cognitive gains. We further hypothesize that cognitive gains will mediate functional improvements.

METHOD

We plan to enroll 360 adults aged 60 years and older who will be randomized to piano training or an active control condition of music listening instruction and complete pre- and immediate post- assessments of CAP, cognition, and everyday function.

Evaluation of dichotic listening performance in normal-hearing, noise-exposed young females

Recent animal studies have shown that intense noise exposures that produce robust temporary threshold shift (TTS) can inflict irreversible damage to the synaptic connections between the inner hair cells and auditory neurons. It was hypothesized that noise-induced cochlear synaptopathy may cause impaired acoustic encoding in the central auditory nervous system leading to impaired speech perception, particularly in challenging listening situations. The aim of the study was to evaluate the influence of high noise exposure background (NEB) on dichotic listening performance, speech-in-noise performance, and auditory brainstem responses (ABR) measured in young females with normal audiograms. The central hypothesis was that individuals with high NEB would exhibit reduced ABR wave I amplitude and subsequently would exhibit poorer performance on speech-in-noise and dichotic listening. In a sample of 32 females (14 with high NEB and 18 with low NEB) aged 18-35 years, the study compared behavioral hearing thresholds (from 250 to 16000 Hz), distortion-product otoacoustic emissions (DPOAEs, 1000-16000 Hz), click-evoked ABR, QuickSIN signal-to-noise ratio (SNR) loss and dichotic digit test (DDT). The results showed no clear association between NEB, and hearing thresholds, DPOAEs, click-evoked ABR measures, and QuickSIN SNR loss. Individuals with high NEB revealed significantly lower DDT scores and evidence of reduced right ear advantage compared to individuals with low NEB. The poorer performance in DDT and the ear asymmetry in DDT scores with normal ABR findings suggest that high NEB might alter the hemispheric organization of speech-sound processing and cognitive control. The clinical significance of the present findings is discussed.

Association of Hearing Loss With Dementia

IMPORTANCE

Hearing loss (HL) may be a modifiable risk factor for dementia, and longitudinal studies are needed to examine the association of HL and dementia.

OBJECTIVE

To investigate the association of HL with incident dementia in Taiwanese adults in the general population.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study collected data from the National Health Insurance Research Database of Taiwan. Patients newly diagnosed with HL from January 1, 2000, through December 31, 2011 (n = 8135), constituted the exposed (HL) group. The HL group patients were matched by sex, age, residence, and insurance premium to individuals without HL (non-HL group) (n = 8135). Data were analyzed from January 1, 2000, to December 31, 2013.

EXPOSURE

Hearing loss defined according to International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes.

MAIN OUTCOMES AND MEASURES

Dementia classified according to ICD-9-CM codes.

RESULTS

Of a total of 16 270 participants (9286 [57.1%] men; mean [SD] age, 65.2 [11.1] years), 1868 developed dementia. The dementia incidence rate in the HL group was higher than that in the non-HL group (19.38 [95% CI, 18.25-20.57] per 1000 person-years vs 13.98 [95% CI, 13.01-15.00] per 1000 person-years) during the follow-up period. In the fully adjusted multivariate Cox proportional hazards regression model applied for risk analysis, patients with HL had a significant risk of dementia (hazard ratio [HR], 1.17; 95% CI, 1.07-1.29; false discovery rate [FDR] P = .003). Subgroup analysis revealed that, among 3 age groups (45-64, 65-74, and ≥75 years), the group aged 45 to 64 years was associated with a risk of dementia (HR, 2.21 [95% CI, 1.57-3.12]; FDR P < .001). In sensitivity analysis, the presence of HL among those aged 45 to 64 years (HR, 1.40; 95% CI, 1.12-1.75; FDR P = .01) was associated with a risk of dementia.

CONCLUSIONS AND RELEVANCE

In this study, hearing loss was positively associated with a risk of dementia, especially in patients aged 45 to 64 years. Hearing protection, screening, and treatment may be used as strategies for mitigating this potential risk factor.

Hearing Loss and Cognition Among Older Adults in a Han Chinese Cohort

Presbycusis (PC) is associated with cognitive decline and incident dementia. Speech reception thresholds (SRT) are used to assess speech detection, which points toward a central component of PC. However, to the best of our knowledge, no previous study has reported the relationship between SRT and cognitive function in older adults in a Han Chinese cohort. Therefore, in this study, we investigate the association of hearing loss, indexed using pure tone average (PTA) and SRT, with cognitive function in a Han Chinese cohort using a standardized neurocognitive battery. Subjects (aged ≥60 years) with no history of psychiatric or neurological diseases were recruited. All subjects underwent a battery of neuropsychological and auditory tests. According to the PTA of the better ear, the subjects were further divided into PC and normal PTA (NP) groups. Regression analyses were performed to examine the relationship between cognitive function and hearing loss in the PC and NP groups and all subjects when controlling for age, sex, education level, diabetes, smoking, and hypertension. Cognitive function was significantly associated with PTA and SRT in all subjects. In all subjects, the correlations between non-verbal cognitive scores and SRT were stronger than those between non-verbal cognitive scores and PTA, whereas the correlations between verbal cognitive scores and PTA were stronger than those between verbal cognitive scores and SRT. Moreover, the correlations between PTA or SRT and cognitive function in the PC group were in principle stronger than those in the NP group. Our findings indicate that cognitive function is significantly associated with PTA and SRT in older adults in a Han Chinese cohort. Therefore, SRT could be an important auditory test for exploring cognitive decline in PC and could complement PTA.

The Age-Related Central Auditory Processing Disorder: Silent Impairment of the Cognitive Ear

Age-related hearing loss (ARHL), also called presbycusis, is a progressive disorder affecting hearing functions and among the elderly has been recognized as the third most frequent condition. Among ARHL components, the age-related central auditory processing disorder (CAPD) refers to changes in the auditory network, negatively impacting auditory perception and/or the speech communication performance. The relationship between auditory-perception and speech communication difficulties in age-related CAPD is difficult to establish, mainly because many older subjects have concomitant peripheral ARHL and age-related cognitive changes. In the last two decades, the association between cognitive impairment and ARHL has received great attention. Peripheral ARHL has recently been defined as the modifiable risk factor with the greatest impact on the development of dementia. Even if very few studies have analyzed the relationship between cognitive decline and age-related CAPD, a strong association was highlighted. Therefore, age-related CAPD could be a specific process related to neurodegeneration. Since these two disorders can be concomitant, drawing causal inferences is difficult. The assumption that ARHL, particularly age-related CAPD, may increase the risk of cognitive impairment in the elderly remains unchallenged. This review aims to summarize the evidence of associations between age-related CAPD and cognitive disorders and to define the diagnostic procedure of CAPD in the elderly. Finally, we highlight the importance of tailoring the rehabilitation strategy to this relationship. Future longitudinal studies with larger sample sizes and the use of adequate assessment tools that can disentangle cognitive dysfunction from sensory impairments are warranted.

5XFAD Mice Show Early Onset Gap Detection Deficits

Alzheimer's patients show auditory temporal processing deficits very early in disease progression, before the onset of major cognitive impairments. In addition to potentially contributing to speech perception and communication deficits in patients, this also represents a potential early biomarker for Alzheimer's. For this reason, tests of temporal processing such as gap detection have been proposed as an early diagnosis tool. For a biomarker such as gap detection deficits to have maximum clinical value, it is important to understand what underlying neuropathology it reflects. For example, temporal processing deficits could arise from alterations at cortical, midbrain, or brainstem levels. Mouse models of Alzheimer's disease can provide the ability to reveal in detail the molecular and circuit pathology underlying disease symptoms. Here we tested whether 5XFAD mice, a leading Alzheimer's mouse model, exhibit impaired temporal processing. We found that 5XFAD mice showed robust gap detection deficits. Gap detection deficits were first detectable at about 2 months of age and became progressively worse, especially for males and for longer gap durations. We conclude that 5XFAD mice are well-suited to serve as a model for understanding the circuit mechanisms that contribute to Alzheimer's-related gap detection deficits.

Sensorial frailty: age-related hearing loss and the risk of cognitive impairment and dementia in later life

The peripheral hearing alterations and central auditory processing disorder (CAPD) associated with age-related hearing loss (ARHL), may impact cognitive disorders in older age. In older age, ARHL is also a significant marker for frailty, another age-related multidimensional clinical condition with a nonspecific state of vulnerability, reduced multisystem physiological reserve, and decreased resistance to different stressors (i.e. sensorial impairments, psychosocial stress, diseases, injuries). The multidimensional nature of frailty required an approach based on different pathogeneses because this clinical condition may include sensorial, physical, social, nutritional, cognitive, and psychological phenotypes. In the present narrative review, the cumulative epidemiological evidence coming from several longitudinal population-based studies, suggested convincing links between peripheral ARHL and incident cognitive decline and dementia. Moreover, a few longitudinal case-control and population-based studies also suggested that age-related CAPD in ARHL, may be central in determining an increased risk of incident cognitive decline, dementia, and Alzheimer's disease (AD). Cumulative meta-analytic evidence confirmed cross-sectional and longitudinal association of both peripheral ARHL and age-related CAPD with different domains of cognitive functions, mild cognitive impairment, and dementia, while the association with dementia subtypes such as AD and vascular dementia remained unclear. However, ARHL may represent a modifiable condition and a possible target for secondary prevention of cognitive impairment in older age, social isolation, late-life depression, and frailty. Further research is required to determine whether broader hearing rehabilitative interventions including coordinated counseling and environmental accommodations could delay or halt cognitive and global decline in the oldest old with both ARHL and dementia.

A Longitudinal Study of Peripheral and Central Auditory Function in Alzheimer's Disease and in Mild Cognitive Impairment

Background/Aim

Central auditory processing disorder (CAPD) might precede the onset of Alzheimer's disease (AD). A method of evaluating CAPD is the dichotic digits test (DDT). The aim was to address this in a longitudinal setting.

Methods

A total of 136 individuals were assessed with peripheral and central hearing tests at baseline and at 5-year follow-up.

Results

Subjects with AD showed a significant decline in DDT scores of the right ear from baseline to follow-up. The other groups retained high DDT scores. Peripheral auditory function declined as expected according to age.

Conclusions

Our study indicates that DDT performance reflects an ongoing process resulting in dementia.

Association between Frontal-Executive Dysfunction and Speech-in-Noise Perception Deficits in Mild Cognitive Impairment

Background and Purpose

Speech-in-noise perception deficits have been demonstrated in patients with mild cognitive impairment (MCI). However, it remains unclear whether the impairment of speech perception varies between MCI subtypes. The purpose of this study was twofold: 1) to compare speech perception performance among MCI subgroups, and 2) to identify the cognitive domains specifically related to speech-in-noise perception.

Methods

We studied 46 patients with MCI and 39 hearing-threshold-matched cognitively normal elderly (CNE) subjects. Two different patient classifications were used: 1) patients with amnestic mild cognitive impairment (aMCI) (n=21) or nonamnestic mild cognitive impairment (naMCI) (n=25), and 2) patients with frontal-executive dysfunction (FED) (n=16) or without FED (n=30). All of the subjects underwent audiometric, neuropsychological, and speech perception assessments. Speech-in-noise perception was measured using sentence recognition tests in the presence of two types of background noise at four levels.

Results

First, as the level of background noise increased, the MCI with FED group scored lower than both the MCI without FED and CNE groups under both types of noise. Second, both the naMCI and aMCI groups scored lower than the CNE group, but there were no differences between the naMCI and aMCI groups in sentence recognition under any noise conditions. Third, significant correlations were found between sentence recognition and executive function scores both in the MCI groups and in the CNE group.

Conclusions

Our findings suggest that frontal-executive function is strongly related to speech-in-noise perception and that MCI patients with FED have greater deficits in speech-in-noise perception compared to other subgroups of MCI.

Head and neck surgical reconstruction in Operation Iraqi Freedom and Operation Enduring Freedom-Afghanistan: A systematic review

Historically, head and neck injuries constituted 16 to 20% of all nonfatal combat injuries. However, advances in body and vehicle armor in the context of the use of ambushes and improvised explosive devices by enemy combatants have resulted in fewer fatalities from head and neck wounds, and thus the incidence of nonfatal head and neck injuries has risen to as high as 52%. Despite this increase, data regarding specific injury distributions, surgical cases, and approaches to repair are lacking in the current literature. We conducted a study to systematically review the current literature regarding head and neck injuries and reconstructions during Operation Iraqi Freedom and Operation Enduring Freedom-Afghanistan. We found 44 articles that met our inclusion criteria. These articles covered 17,461 head and neck wounds sustained by 12,105 patients. Superficial soft-tissue facial injuries were most common wounds (31.7% of cases), followed by wounds to the neck (25.2%) and midface (17.9%). The 44 articles listed 5,122 discrete surgical reports covering 5,758 procedures. Of these procedures, simple facial laceration repairs (25.2%) and ophthalmologic surgeries (12.1%) were the most common soft-tissue repairs, and mandibular reconstructions (11.3%) were the most common type of bony reconstruction. Major flap reconstructions for coverage were required in only 0.4% of procedures. This information will be valuable for educating those involved in otolaryngology training programs, as well as civilian otolaryngologists regarding the types of injury patterns they should expect to see and treat in the returning veteran population.

Deficit in Central Auditory Processing as a Biomarker of Pre-Clinical Alzheimer's Disease

Prevention of dementia due to Alzheimer's disease (d/AD) requires interventions that slow the disease process prior to symptom onset. To develop such interventions, one needs metrics that assess pre-symptomatic disease progression. Familiar measures of progression include cerebrospinal fluid (CSF) biochemical and imaging analyses, as well as cognitive testing. Changes in the latter can sometimes be difficult to distinguish from effects of "normal" aging. A different approach involves testing of "central auditory processing" (CAP), which enables comprehension of auditory stimuli amidst a distracting background (e.g., conversation in a noisy bar or restaurant). Such comprehension is often impaired in d/AD. Similarly, effortful or diminished auditory comprehension is sometimes reported by cognitively healthy elders, raising the possibility that CAP deficit may be a marker of pre-symptomatic AD. In 187 cognitively and physically healthy members of the aging, AD family history-positive PREVENT-AD cohort, we therefore evaluated whether CAP deficits were associated with known markers of AD neurodegeneration. Such markers included CSF tau concentrations and magnetic resonance imaging volumetric and cortical thickness measures in key AD-related regions. Adjusting for age, sex, education, pure-tone hearing, and APOEɛ4 status, we observed a persistent relationship between CAP scores and CSF tau levels, entorhinal and hippocampal cortex volumes, cortical thickness, and deficits in cognition (Repeatable Battery for Assessment of Neuropsychological Status total score, and several of its index scales). These cross-sectional observations suggest that CAP may serve as a novel metric for pre-symptomatic AD pathogenesis. They are therefore being followed up longitudinally with larger samples.

Cholinergic Hypofunction in Presbycusis-Related Tinnitus With Cognitive Function Impairment: Emerging Hypotheses

Presbycusis (age-related hearing loss) is a potential risk factor for tinnitus and cognitive deterioration, which result in poor life quality. Presbycusis-related tinnitus with cognitive impairment is a common phenotype in the elderly population. In these individuals, the central auditory system shows similar pathophysiological alterations as those observed in Alzheimer's disease (AD), including cholinergic hypofunction, epileptiform-like network synchronization, chronic inflammation, and reduced GABAergic inhibition and neural plasticity. Observations from experimental rodent models indicate that recovery of cholinergic function can improve memory and other cognitive functions via acetylcholine-mediated GABAergic inhibition enhancement, nicotinic acetylcholine receptor (nAChR)-mediated anti-inflammation, glial activation inhibition and neurovascular protection. The loss of cholinergic innervation of various brain structures may provide a common link between tinnitus seen in presbycusis-related tinnitus and age-related cognitive impairment. We hypothesize a key component of the condition is the withdrawal of cholinergic input to a subtype of GABAergic inhibitory interneuron, neuropeptide Y (NPY) neurogliaform cells. Cholinergic denervation might not only cause the degeneration of NPY neurogliaform cells, but may also result in decreased AChR activation in GABAergic inhibitory interneurons. This, in turn, would lead to reduced GABA release and inhibitory regulation of neural networks. Reduced nAChR-mediated anti-inflammation due to the loss of nicotinic innervation might lead to the transformation of glial cells and release of inflammatory mediators, lowering the buffering of extracellular potassium and glutamate metabolism. Further research will provide evidence for the recovery of cholinergic function with the use of cholinergic input enhancement alone or in combination with other rehabilitative interventions to reestablish inhibitory regulation mechanisms of involved neural networks for presbycusis-related tinnitus with cognitive impairment.

Dichotic Digits Test Performance Across the Ages: Results From Two Large Epidemiologic Cohort Studies

OBJECTIVES

The Dichotic Digits test (DDT) has been widely used to assess central auditory processing but there is limited information on observed DDT performance in a general population. The purpose of the study was to determine factors related to DDT performance in a large cohort spanning the adult age range.

DESIGN

The study was cross-sectional and subjects were participants in the Epidemiology of Hearing Loss Study (EHLS), a population-based investigation of age-related hearing loss, or the Beaver Dam Offspring Study (BOSS), a study of aging in the adult offspring of the EHLS members. Subjects seen during the 4th EHLS (2008 to 2010) or the 2nd BOSS (2010 to 2013) examination were included (N = 3655 participants [1391 EHLS, 2264 BOSS]; mean age = 61.1 years, range = 21 to 100 years). The free and right ear-directed recall DDTs were administered using 25 sets of triple-digit pairs with a 70 dB HL presentation level. Pure-tone audiometric testing was conducted and the pure-tone threshold average (PTA) at 0.5, 1, 2, and 4 kHz was categorized using the worse ear: no loss = PTA ≤ 25 dB HL; mild loss = 25 < PTA ≤ 40 dB HL; moderate or marked loss = PTA > 40 dB HL. Cognitive impairment was defined as a Mini-Mental State Examination score < 24 (maximum = 30) or a self- or proxy-reported history of dementia or Alzheimer's disease. Demographic information was self-reported. General linear models were fit and multiple linear regression was performed.

RESULTS

The mean total free recall DDT score was 76.7% (range = 21.3 to 100%). Less than 10% of the participants had a total free recall score below 60% correct. The mean right ear-directed recall score was 98.4% with 69% of the participants scoring 100% and another 15.5% scoring 98.7% (1 incorrect digit). In multivariable modeling of the total free recall scores, the predicted mean free recall score was 1 percentage point lower for every 5-year increase in age, 2.3 percentage points lower in males than females, 8.7 percentage points lower in participants with less than a high school degree than in those with college degrees, 6.8 percentage points lower in participants with a moderate or marked hearing loss compared with no hearing loss, and 8.3 percentage points lower in participants with cognitive impairment compared with those without cognitive impairment. These 5 factors were independently and significantly related to performance and accounted for 22.7% of the total variability in free recall scores.

CONCLUSIONS

Substantial variation in the total free recall DDT scores but very little variation in the right ear-directed recall DDT scores was observed. Age, sex, education, hearing loss severity, and cognitive impairment were found to be significantly related to DDT scores but explained less than 25% of the total variability in total free recall scores. The right ear-directed recall DDT by itself may not be of benefit in assessing central auditory processing in a general population because of its limited variability but further evaluation of factors potentially related to free recall DDT variability may prove useful.

Impact of Aging on the Auditory System and Related Cognitive Functions: A Narrative Review

Age-related hearing loss (ARHL), presbycusis, is a chronic health condition that affects approximately one-third of the world's population. The peripheral and central hearing alterations associated with age-related hearing loss have a profound impact on perception of verbal and non-verbal auditory stimuli. The high prevalence of hearing loss in the older adults corresponds to the increased frequency of dementia in this population. Therefore, researchers have focused their attention on age-related central effects that occur independent of the peripheral hearing loss as well as central effects of peripheral hearing loss and its association with cognitive decline and dementia. Here we review the current evidence for the age-related changes of the peripheral and central auditory system and the relationship between hearing loss and pathological cognitive decline and dementia. Furthermore, there is a paucity of evidence on the relationship between ARHL and established biomarkers of Alzheimer's disease, as the most common cause of dementia. Such studies are critical to be able to consider any causal relationship between dementia and ARHL. While this narrative review will examine the pathophysiological alterations in both the peripheral and central auditory system and its clinical implications, the question remains unanswered whether hearing loss causes cognitive impairment or vice versa.

An Epidemiologic Study of the Association between Free Recall Dichotic Digits Test Performance and Vascular Health

BACKGROUND

Associations between vascular health-related factors and hearing loss defined using audiometric pure-tone thresholds have been found. Studies have not focused on a potential relationship between vascular health-related factors and central auditory processing.

PURPOSE

The aim of this study was to evaluate, on a population level, the relationship of vascular health-related factors with central auditory function.

RESEARCH DESIGN

A cross-sectional, population study.

STUDY SAMPLE

Subjects were participants in the Epidemiology of Hearing Loss Study (EHLS) or the Beaver Dam Offspring Study (BOSS)-prospective studies of aging and sensory loss. BOSS participants were the adult offspring of participants in the EHLS. Participants who completed the Dichotic Digits Test (DDT) during the fourth examination period of the EHLS (2008-2010) or the second examination period of the BOSS (2010-2013) were included (n = 3,655, mean age = 61.1 years).

DATA COLLECTION AND ANALYSIS

The DDT-free recall test was conducted using 25 sets of triple-digit pairs at a 70 dB HL presentation level. The total number of correctly repeated digits from the right and left ears was converted to a percentage correct and used as an outcome. The percentage correct in the left ear was subtracted from the percentage correct in the right ear and used as an outcome. Vascular health-related measures obtained during the examination included blood pressure, mean carotid intima-media thickness, femoral pulse wave velocity (PWV), hemoglobin A1C, and non-high-density lipoprotein (HDL) cholesterol, and, in the EHLS participants, C-reactive protein and interleukin-6. Information on vascular health-related history and behaviors was self-reported. General linear modeling produced estimates of the age- and sex-adjusted least squares means for each vascular factor, and multiple linear regression was used for multivariable modeling of each outcome.

RESULTS

After multivariable adjustment, participants with diabetes had a significantly lower (worse) mean DDT-free recall total score (-2.08 percentage points, p < 0.001) than those without diabetes. Participants who exercised at least once per week had a significantly higher (better) mean DDT-free recall total score (+1.07 percentage points, p < 0.01) than those who did not exercise at least once per week. Alcohol consumption was associated with a higher DDT-free recall total score (+0.15 percentage points per +25 g ethanol, p < 0.01). In multivariable modeling of the right-left ear difference in DDT-free recall scores, participants with a history of cardiovascular disease (CVD) or higher PWV demonstrated significantly larger differences (CVD: +3.11 percentage points, p = 0.02; PWV: +0.36 percentage points per 1 m/sec, p < 0.01). Higher levels of non-HDL cholesterol were associated with smaller right-left ear differences (-0.22 percentage points per 10 mg/dL, p = 0.01). Adjustment for handedness did not affect the results.

CONCLUSIONS

Vascular health-related factors may play a role in central auditory function.

Impairment of the Missing Fundamental Phenomenon in Individuals with Alzheimer’s Disease: A Neuropsychological and Voxel-Based Morphometric Study

Background/Aims

The missing fundamental phenomenon (MFP) is a universal pitch perception illusion that occurs in animals and humans. In this study, we aimed to determine whether the MFP is impaired in patients with Alzheimer's disease (AD) using an auditory pitch perception experiment. We further examined anatomical correlates of the MFP in patients with AD by measuring gray matter volume (GMV) on magnetic resonance images via voxel-based morphometric analysis.

Methods

We prospectively enrolled 29 patients with AD and 20 healthy older adults. Auditory stimuli included 12 melodies of Japanese nursery songs that were expected to be familiar to participants. We constructed the melodies using pure and missing fundamental tones (MFTs).

Results

Patients with AD exhibited significantly poorer performance on the MFT task than healthy controls. MFT scores were positively correlated with GMV in the bilateral insula and temporal poles, left inferior frontal gyrus, right entorhinal cortex, and right cerebellum.

Conclusions

These results suggest that impairments in the MFP represent a manifestation of the degeneration of auditory-related brain regions in AD. Further studies are required to more fully elucidate the neural mechanisms underlying auditory impairments in patients with AD and related dementia disorders.

A European Perspective on Auditory Processing Disorder-Current Knowledge and Future Research Focus

Current notions of “hearing impairment,” as reflected in clinical audiological practice, do not acknowledge the needs of individuals who have normal hearing pure tone sensitivity but who experience auditory processing difficulties in everyday life that are indexed by reduced performance in other more sophisticated audiometric tests such as speech audiometry in noise or complex non-speech sound perception. This disorder, defined as “Auditory Processing Disorder” (APD) or “Central Auditory Processing Disorder” is classified in the current tenth version of the International Classification of diseases as H93.25 and in the forthcoming beta eleventh version. APDs may have detrimental effects on the affected individual, with low esteem, anxiety, and depression, and symptoms may remain into adulthood. These disorders may interfere with learning per se and with communication, social, emotional, and academic-work aspects of life. The objective of the present paper is to define a baseline European APD consensus formulated by experienced clinicians and researchers in this specific field of human auditory science. A secondary aim is to identify issues that future research needs to address in order to further clarify the nature of APD and thus assist in optimum diagnosis and evidence-based management. This European consensus presents the main symptoms, conditions, and specific medical history elements that should lead to auditory processing evaluation. Consensus on definition of the disorder, optimum diagnostic pathway, and appropriate management are highlighted alongside a perspective on future research focus.

Data-Driven Sequence of Changes to Anatomical Brain Connectivity in Sporadic Alzheimer's Disease

Model-based investigations of transneuronal spreading mechanisms in neurodegenerative diseases relate the pattern of pathology severity to the brain's connectivity matrix, which reveals information about how pathology propagates through the connectivity network. Such network models typically use networks based on functional or structural connectivity in young and healthy individuals, and only end-stage patterns of pathology, thereby ignoring/excluding the effects of normal aging and disease progression. Here, we examine the sequence of changes in the elderly brain's anatomical connectivity over the course of a neurodegenerative disease. We do this in a data-driven manner that is not dependent upon clinical disease stage, by using event-based disease progression modeling. Using data from the Alzheimer's Disease Neuroimaging Initiative dataset, we sequence the progressive decline of anatomical connectivity, as quantified by graph-theory metrics, in the Alzheimer's disease brain. Ours is the first single model to contribute to understanding all three of the nature, the location, and the sequence of changes to anatomical connectivity in the human brain due to Alzheimer's disease. Our experimental results reveal new insights into Alzheimer's disease: that degeneration of anatomical connectivity in the brain may be a viable, even early, biomarker and should be considered when studying such neurodegenerative diseases.

Hearing Impairment, Mild Cognitive Impairment, and Dementia: A Meta-Analysis of Cohort Studies

BACKGROUND

To estimate a pooled association between hearing impairment and risk of mild cognitive impairment and dementia.

METHODS

PubMed, Embase, and Web of Science were searched for prospective cohort studies that examined the association between hearing impairment and risk of mild cognitive impairment and/or dementia. Random-effects models were fitted to estimate the summary risk ratios (RRs) and 95% confidence interval (CIs), which represents the pooled association between hearing impairment with risk of mild cognitive impairment and dementia, compared to subjects free of hearing impairment.

RESULTS

Four studies on hearing impairment with mild cognitive impairment and 7 studies on hearing impairment with dementia were included in the meta-analysis. A total of 15,521 subjects were studied with follow-up periods between 2 and 16.8 years. Hearing impairment was associated with a greater risk of mild cognitive impairment (RR = 1.30, 95% CI: 1.12, 1.51) and dementia (RR = 2.39, 95% CI: 1.58, 3.61).

CONCLUSIONS

The meta-analysis showed that hearing impairment is associated with a higher risk of mild cognitive impairment and dementia among older adults.

Association of Hearing Impairment and Subsequent Driving Mobility in Older Adults

Purpose of the Study

Hearing impairment (HI) is associated with driving safety (e.g., increased crashes and poor on-road driving performance). However, little is known about HI and driving mobility. This study examined the longitudinal association of audiometric hearing with older adults' driving mobility over 3 years.

Design and Methods

Secondary data analyses were conducted of 500 individuals (63-90 years of age) from the Staying Keen in Later Life (SKILL) study. Hearing (pure tone average of 0.5, 1, and 2kHz) was assessed in the better hearing ear and categorized into normal hearing ≤25 dB hearing level (HL); mild HI 26-40 dB HL; or moderate and greater HI ≥41 dB HL. The Useful Field of View Test (UFOV) was used to estimate the risk for adverse driving events. Multivariate analysis of covariance compared driving mobility between HI levels across time, adjusting for age, sex, race, hypertension, and stroke. Adjusting for these same covariates, Cox regression analyses examined incidence of driving cessation by HI across 3 years.

Results

Individuals with moderate or greater HI performed poorly on the UFOV, indicating increased risk for adverse driving events (p < .001). No significant differences were found among older adults with varying levels of HI for driving mobility (p values > .05), including driving cessation rates (p = .38), across time.

Implications

Although prior research indicates older adults with HI may be at higher risk for crashes, they may not modify driving over time. Further exploration of this issue is required to optimize efforts to improve driving safety and mobility among older adults.

Auditory Processing of Older Adults With Probable Mild Cognitive Impairment

PURPOSE

Studies suggest that deficits in auditory processing predict cognitive decline and dementia, but those studies included limited measures of auditory processing. The purpose of this study was to compare older adults with and without probable mild cognitive impairment (MCI) across two domains of auditory processing (auditory performance in competing acoustic signals and temporal aspects of audition).

METHOD

The Montreal Cognitive Assessment (Nasreddine et al., 2005) was used to classify participants as with or without probable MCI. In this cross-sectional study, participants (n = 79) completed 4 measures of auditory processing: Synthetic Sentence Identification with Ipsilateral Competing Message (Gates, Beiser, Rees, D'Agostino, & Wolf, 2002), Dichotic Sentence Identification (Fifer, Jerger, Berlin, Tobey, & Campbell, 1983), Adaptive Tests of Temporal Resolution (ATTR; Lister & Roberts, 2006; across-channel and within-channel subtests), and time-compressed speech (Wilson, 1993; Wilson, Preece, Salamon, Sperry, & Bornstein, 1994). Audiometry was also conducted.

RESULTS

Those with probable MCI had significantly poorer performance than those without MCI on Synthetic Sentence Identification with Ipsilateral Competing Message, Dichotic Sentence Identification, and the ATTR within-channel subtest. No group differences were found for time-compressed speech, ATTR across-channel, or audiometric measures.

CONCLUSIONS

Older adults with cognitive impairment not only have difficulty with competing acoustic signals but may also show poor temporal processing. The profile of auditory processing deficits among older adults with cognitive impairment may include multiple domains.

[Impaired recognition of environmental sounds in patients with dementia : I can hear but I do not understand]

BACKGROUND

Impairment of central auditory processing is a well-known symptom of neurodegenerative dementia; however, whilst numerous studies have examined verbal processing impairment, to date few have attempted to describe impairments of non-verbal, environmental sound recognition in patients with dementia. As these impairments may have direct implications on patient support and care, such studies are urgently necessary.

AIM OF THE STUDY

The aim of the study was to determine whether the recognition of meaningful environmental sounds is impaired in patients with mild or early stage neurodegenerative dementia.

PATIENTS AND METHODS

We developed a test of non-verbal sound recognition consisting of 16 sound sequences from the familiar and unfamiliar environments. We included 18 patients with mild cognitive impairment and mild dementia caused by Alzheimer's disease and frontotemporal dementia, as well as 20 cognitively healthy controls.

RESULTS

Patients and controls were given the test of recognizing 16 meaningful sounds from the familiar and unfamiliar environments. Patients with dementia performed significantly worse in comparison to cognitively healthy controls. Whilst healthy controls correctly recognized on average 12.1 ± 2.2 out of 16 sounds, cognitively impaired patients recognized 9.2 ± 2.5. Correlation analysis showed that the mini mental state examination (MMSE) scores were positively correlated with the number of correctly recognized sounds (MMSE: r = 0.556, p = 0.017).

DISCUSSION

The fact that even in mild stages of Alzheimer's disease or frontotemporal dementia patients either do not recognize or misinterpret environmental sounds must be taken into consideration not only in everyday life but in particular when patients need to leave their familiar living environment, whether temporarily (e. g. hospitalization) or permanently (e. g. nursing home admission).

Sensorineural Organs Dysfunction and Cognitive Decline: A Review Article

Vision, hearing, olfaction, and cognitive function are essential components of healthy and successful aging. Multiple studies demonstrate relationship between these conditions with cognitive function. The present article focuses on hearing loss, visual impairment, olfactory loss, and dual sensory impairments in relation to cognitive declination and neurodegenerative disorders. Sensorineural organ impairment is a predictive factor for mild cognitive impairment and neurodegenerative disorders in the elderly. We recommend early detection of sensorineural dysfunction by history, physical examination, and screening tests. Assisted device and early cognitive rehabilitation may be beneficial. Future research is warranted in order to explore advanced treatment options and method to slow progression for cognitive declination and sensorineural organ impairment.