Association of hearing impairment with brain volume changes in older adults

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.

An Exploration of the Associations Among Hearing Loss, Physical Health, and Visual Memory in Adults From West Central Alabama

PURPOSE

The purpose of this preliminary study was to explore the associations among hearing loss, physical health, and visual memory in adults living in rural areas, urban clusters, and an urban city in west Central Alabama.

METHOD

Two hundred ninety-seven adults (182 women, 115 men) from rural areas, urban clusters, and an urban city of west Central Alabama completed a hearing assessment, a physical health questionnaire, a hearing handicap measure, and a visual memory test.

RESULTS

A greater number of adults with hearing loss lived in rural areas and urban clusters than in an urban area. In addition, poorer physical health was significantly associated with hearing loss. A greater number of individuals with poor physical health who lived in rural towns and urban clusters had hearing loss compared with the adults with other physical health issues who lived in an urban city. Poorer hearing sensitivity resulted in poorer outcomes on the Emotional and Social subscales of the Hearing Handicap Inventory for Adults. And last, visual memory, a working-memory task, was not associated with hearing loss but was associated with educational level.

CONCLUSIONS

The outcomes suggest that hearing loss is associated with poor physical and emotional health but not with visual-memory skills. A greater number of adults living in rural areas experienced hearing loss compared with adults living in an urban city, and consequently, further research will be necessary to confirm this relationship and to explore the reasons behind it. Also, further exploration of the relationship between cognition and hearing loss in adults living in rural and urban areas will be needed.

Older Adults With a Combination of Vision and Hearing Impairment Experience Higher Rates of Cognitive Impairment, Functional Dependence, and Worse Outcomes Across a Set of Quality Indicators

Objectives: Hearing and vision impairment were examined across several health-related outcomes and across a set of quality indicators (QIs) in home care clients with both vision and hearing loss (or dual sensory impairment [DSI]). Method: Data collected using the Resident Assessment Instrument for Home Care (RAI-HC) were analyzed in a sample of older home care clients. The QIs represent the proportion of clients experiencing negative outcomes (e.g., falls, social isolation). Results: The average age of clients was 82.8 years ( SD = 7.9), 20.5% had DSI and 8.5% had a diagnosis of Alzheimer’s disease (AD). Clients with DSI were more likely to have a diagnosis of dementia (not AD), have functional impairments, report loneliness, and have higher rates across 20 of the 22 QIs, including communication difficulty and cognitive decline. Clients with highly impaired hearing, and any visual impairment, had the highest QI rates. Discussion: Individuals with DSI experience higher rates of adverse events across many health-related outcomes and QIs. Understanding the unique contribution of hearing and vision in this group can promote optimal quality of care.

A novel method of quantifying brain atrophy associated with age-related hearing loss

A growing body of evidence has shown that a relationship between age-related hearing loss and structural brain changes exists. However, a method to measure brain atrophy associated with hearing loss from a single MRI study (i.e. without an interval study) that produces an independently interpretable output does not. Such a method would be beneficial for studying patterns of structural brain changes on a large scale. Here, we introduce our method for this.

Audiometric evaluations and mini-mental state exams were obtained in 34 subjects over the age of 80 who have had brain MRIs in the past 6 years. CSF and parenchymal brain volumes (whole brain and by lobe) were obtained through a novel, fully automated algorithm. Atrophy was calculated by taking the ratio of CSF to parenchyma. High frequency hearing loss was associated with disproportional temporal lobe atrophy relative to whole brain atrophy independent of age (r = 0.471, p = 0.005). Mental state was associated with frontoparietal atrophy but not to temporal lobe atrophy, which is consistent with known results. Our method demonstrates that hearing loss is associated with temporal lobe atrophy and generalized whole brain atrophy. Our algorithm is efficient, fully automated, and able to detect significant associations in a small cohort.

•

A novel, fully automated method measuring brain atrophy using CSF to brain parenchymal volume ratios is introduced.

•

Brain atrophy is obtained from a single MRI study and unlike brain volume, is interpretable without relative comparison.

•

Age-related hearing loss is significantly associated with both temporal lobe and generalized whole brain atrophy.

Hearing Impairment and Incident Dementia: Findings from the English Longitudinal Study of Ageing

OBJECTIVES

To determine whether hearing loss is associated with incident physician-diagnosed dementia in a representative sample.

DESIGN

Retrospective cohort study.

SETTING

English Longitudinal Study of Ageing.

PARTICIPANTS

Adults aged 50 and older.

MEASUREMENTS

Cross-sectional associations between self-reported (n = 7,865) and objective hearing measures (n = 6,902) and dementia were examined using multinomial-logistic regression. The longitudinal association between self-reported hearing at Wave 2 (2004/05) and cumulative physician-diagnosed dementia up to Wave 7 (2014/15) was modelled using Cox proportional hazards regression.

RESULTS

After adjustment for potential confounders, in cross-sectional analysis, participants who had self-reported or objective moderate and poor hearing were more likely to have a dementia diagnosis than those with normal hearing (self-reported: odds ratio OR = 1.6, 95% CI = 1.1-2.4 moderate hearing; OR = 2.6, 95% CI = 1.7-3.9 poor hearing, objective: OR = 1.6, 95% CI = 1.0-2.8 moderate hearing; OR = 4.4, 95% CI = 1.9-9.9 poor hearing). Longitudinally, the hazard of developing dementia was 1.4 (95% CI = 1.0-1.9) times as high in individuals who reported moderate hearing and 1.6 (95% CI = 1.1-2.0) times as high in those who reported poor hearing.

CONCLUSION

Older adults with hearing loss are at greater risk of dementia than those with normal hearing. These findings are consistent with the rationale that correction of hearing loss could help delay the onset of dementia, or that hearing loss itself could serve as a risk indicator for cognitive decline.

Does treating hearing loss prevent or slow the progress of dementia? Hearing is not all in the ears, but who's listening?

Since hearing loss is strongly linked to cognitive decline, treating hearing impairment may have the potential to prevent the onset or slow the progress of dementia.

Music Training and Education Slow the Deterioration of Music Perception Produced by Presbycusis in the Elderly

The perception of music depends on the normal function of the peripheral and central auditory system. Aged subjects without hearing loss have altered music perception, including pitch and temporal features. Presbycusis or age-related hearing loss is a frequent condition in elderly people, produced by neurodegenerative processes that affect the cochlear receptor cells and brain circuits involved in auditory perception. Clinically, presbycusis patients have bilateral high-frequency hearing loss and deteriorated speech intelligibility. Music impairments in presbycusis subjects can be attributed to the normal aging processes and to presbycusis neuropathological changes. However, whether presbycusis further impairs music perception remains controversial. Here, we developed a computerized version of the Montreal battery of evaluation of amusia (MBEA) and assessed music perception in 175 Chilean adults aged between 18 and 90 years without hearing complaints and in symptomatic presbycusis patients. We give normative data for MBEA performance in a Latin-American population, showing age and educational effects. In addition, we found that symptomatic presbycusis was the most relevant factor determining global MBEA accuracy in aged subjects. Moreover, we show that melodic impairments in presbycusis individuals were diminished by music training, while the performance in temporal tasks were affected by the educational level and music training. We conclude that music training and education are important factors as they can slow the deterioration of music perception produced by age-related hearing loss.

HearCARE: Hearing and Communication Assistance for Resident Engagement

Impaired hearing is related to poor health outcomes, including compromised cognitive function, in aging individuals. Hearing loss is the third most common chronic health condition after arthritis and heart disease in older adults and the fourth most detrimental condition related to quality of life in older adults. Only 18% of aging adults who have impactful hearing loss actually use custom-fit amplification. Therefore, the majority of aging individuals entering senior living facilities will have untreated hearing loss. Older adults move to senior communities to maintain or increase their social engagement, to receive care from qualified staff, and to ultimately enhance their quality of life. We know that the majority of individuals over 65 years of age have significant hearing loss, which leaves them with complex listening needs due to low incidence of hearing aid use, group communication situations that are common for social activities, interactive dining environments, and the need for telephone use to connect with loved ones. Busy staff and family members may not be aware of the impact of decreased hearing on quality of life, as well as caregiver burden. HearCARE (Hearing and Communication Assistance for Resident Engagement) is an initiative to provide communication assistance on a day-to-day basis in senior living facilities in a cost-effective manner. This innovative model for delivering audiology services and communication assistance in senior living communities employing communication facilitators who are trained and supervised by an audiologist will be described. Data related to the communication facilitator training, daily activities, interactions with the audiologist, use of devices, and impact on residents, staff, and families will be described.

Hearing Impairment and Incident Dementia and Cognitive Decline in Older Adults: The Health ABC Study

BACKGROUND

Age-related peripheral hearing impairment (HI) is prevalent, treatable, and may be a risk factor for dementia in older adults. In prospective analysis, we quantified the association of HI with incident dementia and with domain-specific cognitive decline in memory, perceptual speed, and processing speed.

METHODS

Data were from the Health, Aging and Body Composition (Health ABC) study, a biracial cohort of well-functioning adults aged 70-79 years. Dementia was defined using a prespecified algorithm incorporating medication use, hospital records, and neurocognitive test scores. A pure-tone average in decibels hearing level (dBHL) was calculated in the better hearing ear using thresholds from 0.5 to 4kHz, and HI was defined as normal hearing (≤25 dBHL), mild (26-40 dBHL), and moderate/severe (>40 dBHL). Associations between HI and incident dementia and between HI and cognitive change were modeled using Cox proportional hazards models and linear mixed models, respectively.

RESULTS

Three-hundred eighty seven (20%) participants had moderate/severe HI, and 716 (38%) had mild HI. After adjustment for demographic and cardiovascular factors, moderate/severe audiometric HI (vs. normal hearing) was associated with increased risk of incident dementia over 9 years (hazard ratio: 1.55, 95% confidence interval [CI]: 1.10, 2.19). Other than poorer baseline memory performance (difference of -0.24 SDs, 95% CI: -0.44, -0.04), no associations were observed between HI and rates of domain-specific cognitive change during 7 years of follow-up.

CONCLUSIONS

HI is associated with increased risk of developing dementia in older adults. Randomized trials are needed to determine whether treatment of hearing loss could postpone dementia onset in older adults.

Observed Hearing Loss and Incident Dementia in a Multiethnic Cohort

OBJECTIVES

To determine whether observed hearing loss (OHL) is associated with incident dementia in a multiethnic population.

DESIGN

Prospective epidemiological cohort study.

SETTING

Community in northern Manhattan.

PARTICIPANTS

Participants in the Washington Heights-Inwood Columbia Aging Project, a longitudinal study on aging and dementia in an ethnically diverse community (n = 1,881).

MEASUREMENTS

OHL was defined when the examiner observed it or according to self-reported hearing aid use. A consensus panel diagnosed dementia using standard research criteria. A Cox proportional hazards model was used to examine the relationship between OHL at baseline and risk of incident dementia (mean 7.3 ± 4.4 years of longitudinal followup, range 0.9-20 years).

RESULTS

OHL was associated with 1.69 (95% confidence interval (CI) = 1.3-2.3, P < .010) times the risk of incident dementia, adjusting for demographic characteristics, cardiovascular risk factors, apolipoprotein E4 genotype, and stroke. When stratified according to race, the association between OHL and incident dementia was high in all groups but was statistically significant only in blacks (hazard ratio = 2.62, 95% CI = 1.5-4.5, P < .010).

CONCLUSION

OHL was associated with greater risk of incident dementia in a multiethnic cohort. More study is needed to determine whether HL contributes to dementia and whether treating HL can reduce the risk of dementia.

Hearing Impairment Is Associated with Smaller Brain Volume in Aging

Although recent studies show that age-related hearing impairment is associated with cerebral changes, data from a population perspective are still lacking. Therefore, we studied the relation between hearing impairment and brain volume in a large elderly cohort. From the population-based Rotterdam Study, 2,908 participants (mean age 65 years, 56% female) underwent a pure-tone audiogram to quantify hearing impairment. By performing MR imaging of the brain we quantified global and regional brain tissue volumes (total brain volume, gray matter volume, white matter (WM) volume, and lobe-specific volumes). We used multiple linear regression models, adjusting for age, sex, head size, time between hearing test and MR imaging, and relevant cognitive and cardiovascular covariates. Furthermore, we performed voxel-based morphometry to explore sub-regional differences. We found that a higher pure-tone threshold was associated with a smaller total brain volume [difference in standardized brain volume per decibel increase in hearing threshold in the age-sex adjusted model: -0.003 (95% confidence interval -0.004; -0.001)]. Specifically, WM volume was associated. Both associations were more pronounced in the lower frequencies. All associations were consistently present in all brain lobes in the lower frequencies and in most lobes in the higher frequencies, and were independent of cognitive function and cardiovascular risk factors. In voxel-based analyses we found associations of hearing impairment with smaller white volumes and some smaller and larger gray volumes, yet these were statistically non-significant. Our findings demonstrate that hearing impairment in elderly is related to smaller total brain volume, independent of cognition and cardiovascular risk factors. This mainly seems to be driven by smaller WM volume, throughout the brain.

Plasticity in bilateral superior temporal cortex: Effects of deafness and cochlear implantation on auditory and visual speech processing

While many individuals can benefit substantially from cochlear implantation, the ability to perceive and understand auditory speech with a cochlear implant (CI) remains highly variable amongst adult recipients. Importantly, auditory performance with a CI cannot be reliably predicted based solely on routinely obtained information regarding clinical characteristics of the CI candidate. This review argues that central factors, notably cortical function and plasticity, should also be considered as important contributors to the observed individual variability in CI outcome. Superior temporal cortex (STC), including auditory association areas, plays a crucial role in the processing of auditory and visual speech information. The current review considers evidence of cortical plasticity within bilateral STC, and how these effects may explain variability in CI outcome. Furthermore, evidence of audio-visual interactions in temporal and occipital cortices is examined, and relation to CI outcome is discussed. To date, longitudinal examination of changes in cortical function and plasticity over the period of rehabilitation with a CI has been restricted by methodological challenges. The application of functional near-infrared spectroscopy (fNIRS) in studying cortical function in CI users is becoming increasingly recognised as a potential solution to these problems. Here we suggest that fNIRS offers a powerful neuroimaging tool to elucidate the relationship between audio-visual interactions, cortical plasticity during deafness and following cochlear implantation, and individual variability in auditory performance with a CI.

Cross-modal plasticity in developmental and age-related hearing loss: Clinical implications

This review explores cross-modal cortical plasticity as a result of auditory deprivation in populations with hearing loss across the age spectrum, from development to adulthood. Cross-modal plasticity refers to the phenomenon when deprivation in one sensory modality (e.g. the auditory modality as in deafness or hearing loss) results in the recruitment of cortical resources of the deprived modality by intact sensory modalities (e.g. visual or somatosensory systems). We discuss recruitment of auditory cortical resources for visual and somatosensory processing in deafness and in lesser degrees of hearing loss. We describe developmental cross-modal re-organization in the context of congenital or pre-lingual deafness in childhood and in the context of adult-onset, age-related hearing loss, with a focus on how cross-modal plasticity relates to clinical outcomes. We provide both single-subject and group-level evidence of cross-modal re-organization by the visual and somatosensory systems in bilateral, congenital deafness, single-sided deafness, adults with early-stage, mild-moderate hearing loss, and individual adult and pediatric patients exhibit excellent and average speech perception with hearing aids and cochlear implants. We discuss a framework in which changes in cortical resource allocation secondary to hearing loss results in decreased intra-modal plasticity in auditory cortex, accompanied by increased cross-modal recruitment of auditory cortices by the other sensory systems, and simultaneous compensatory activation of frontal cortices. The frontal cortices, as we will discuss, play an important role in mediating cognitive compensation in hearing loss. Given the wide range of variability in behavioral performance following audiological intervention, changes in cortical plasticity may play a valuable role in the prediction of clinical outcomes following intervention. Further, the development of new technologies and rehabilitation strategies that incorporate brain-based biomarkers may help better serve hearing impaired populations across the lifespan.

Hearing and dementia

Hearing deficits associated with cognitive impairment have attracted much recent interest, motivated by emerging evidence that impaired hearing is a risk factor for cognitive decline. However, dementia and hearing impairment present immense challenges in their own right, and their intersection in the auditory brain remains poorly understood and difficult to assess. Here, we outline a clinically oriented, symptom-based approach to the assessment of hearing in dementias, informed by recent progress in the clinical auditory neuroscience of these diseases. We consider the significance and interpretation of hearing loss and symptoms that point to a disorder of auditory cognition in patients with dementia. We identify key auditory characteristics of some important dementias and conclude with a bedside approach to assessing and managing auditory dysfunction in dementia.

The Longitudinal Impact of Hearing Impairment on Cognition Differs According to Cognitive Domain

Identification and modification of the risk factors for cognitive decline throughout the adult life span are priority subjects in a progressively aging society; however, much remains to be learned. The aim of this study was to understand whether changes in cognitive function can be affected by hearing impairment (HI) and whether the impact of HI differs depending on the cognitive domain. A total of 1109 individuals aged 60-79 years at baseline who participated in the Longitudinal Study of Aging at the National Institute for Longevity Sciences (NILS-LSA) was followed up for a maximum of 13.3 years. Cognitive function was evaluated using four subtests of the Japanese Wechsler Adult Intelligence Scale-Revised Short Forms (JWAIS-R-SF): namely, Information, Similarities, Picture Completion, and the Digit Symbol Substitution subtests. The HI was defined as a pure-tone average of the better ear >25 dB. A longitudinal analysis of 4437 observations obtained during a follow-up period of approximately 12 years was performed. We estimated linear changes in subtest scores by HI status, using the time-varying mixed-effects regression model, which included fixed terms for the intercept, HI status at baseline, time (years elapsed since baseline) and an HI × time interaction term adjusted for age at baseline, sex, education, and other possible confounders. There were significant main effects of HI on the scores of the four subtests after adjustment. The HI × time interaction was significant for the scores of the Information (p = 0.001) and Digit Symbol Substitution subtests (p = 0.001). The scores of the HI group declined faster in the Information and Digit Symbol Substitution subtests compared to those in the no-HI group. The model-predicted 12-year slope using a mean baseline age (68.7 years) indicated no significant decline in the individuals without HI at baseline for the Information and Similarities subtests, however, this tolerance was lost in the individuals with HI. In conclusion, the present observation showed that the impact of HI on cognition was longitudinally significant and implied that the effect differs according to cognitive domain.

Interventional Audiology: Broadening the Scope of Practice to Meet the Changing Demands of the New Consumer

Given the growth in the aging population, low hearing uptake rates and the emerging science indicating that age-related hearing loss has long term consequences to health and wellness, an interventional audiology strategy is needed. This paper will define interventional audiology and offer guidance on bringing an interventional audiology to life in clinical practice.

Hearing, Cognition, and Healthy Aging: Social and Public Health Implications of the Links between Age-Related Declines in Hearing and Cognition

Sensory input provides the signals used by the brain when listeners understand speech and participate in social activities with other people in a range of everyday situations. When sensory inputs are diminished, there can be short-term consequences to brain functioning, and long-term deprivation can affect brain neuroplasticity. Indeed, the association between hearing loss and cognitive declines in older adults is supported by experimental and epidemiologic evidence, although the causal mechanisms remain unknown. These interactions of auditory and cognitive aging play out in the challenges confronted by people with age-related hearing problems when understanding speech and engaging in social interactions. In the present article, we use the World Health Organization's International Classification of Functioning, Disability and Health and the Selective Optimization with Compensation models to highlight the importance of adopting a healthy aging perspective that focuses on facilitating active social participation by older adults. First, we examine epidemiologic evidence linking ARHL to cognitive declines and other health issues. Next, we examine how social factors influence and are influenced by auditory and cognitive aging and if they may provide a possible explanation for the association between ARHL and cognitive decline. Finally, we outline how audiologists could reposition hearing health care within the broader context of healthy aging.

Hearing and Cognitive Impairment and the Role of the International Classification of Functioning, Disability and Health as a Rehabilitation Framework

The International Classification of Functioning, Disability and Health (ICF) has been applied widely in the literature to describe and differentiate the broad implications of hearing impairment (HI) and cognitive impairment (CI) on communication. As CI and HI are largely age-related conditions, the likelihood of comorbidity of these conditions is high. In the context of an aging population, the prevalence of comorbidity is likely to rise, yet much of the clinical assessment and intervention in HI and CI occur separately. The benefit of addressing the dual impact of these conditions is of increasing clinical importance for all clinicians working with older adults and for audiologists and speech pathologists in particular. In this article, the ICF model will be applied to explore the everyday implications of HI and CI. Furthermore, the clinical implications of the ICF model are explored with particular respect to communication assessment and intervention options. The potential benefit of combining activity- and participation-focused interventions currently offered for HI and CI independently is examined.

Linking cognitive and visual perceptual decline in healthy aging: The information degradation hypothesis

Several hypotheses attempt to explain the relation between cognitive and perceptual decline in aging (e.g., common-cause, sensory deprivation, cognitive load on perception, information degradation). Unfortunately, the majority of past studies examining this association have used correlational analyses, not allowing for these hypotheses to be tested sufficiently. This correlational issue is especially relevant for the information degradation hypothesis, which states that degraded perceptual signal inputs, resulting from either age-related neurobiological processes (e.g., retinal degeneration) or experimental manipulations (e.g., reduced visual contrast), lead to errors in perceptual processing, which in turn may affect non-perceptual, higher-order cognitive processes. Even though the majority of studies examining the relation between age-related cognitive and perceptual decline have been correlational, we reviewed several studies demonstrating that visual manipulations affect both younger and older adults' cognitive performance, supporting the information degradation hypothesis and contradicting implications of other hypotheses (e.g., common-cause, sensory deprivation, cognitive load on perception). The reviewed evidence indicates the necessity to further examine the information degradation hypothesis in order to identify mechanisms underlying age-related cognitive decline.

Neural Alterations in Acquired Age-Related Hearing Loss

Hearing loss is one of the most prevalent chronic health conditions in older adults. Growing evidence suggests that hearing loss is associated with reduced cognitive functioning and incident dementia. In this mini-review, we briefly examine literature on anatomical and functional alterations in the brains of adults with acquired age-associated hearing loss, which may underlie the cognitive consequences observed in this population, focusing on studies that have used structural and functional magnetic resonance imaging, diffusion tensor imaging, and event-related electroencephalography. We discuss structural and functional alterations observed in the temporal and frontal cortices and the limbic system. These neural alterations are discussed in the context of common cause, information-degradation, and sensory-deprivation hypotheses, and we suggest possible rehabilitation strategies. Although, we are beginning to learn more about changes in neural architecture and functionality related to age-associated hearing loss, much work remains to be done. Understanding the neural alterations will provide objective markers for early identification of neural consequences of age-associated hearing loss and for evaluating benefits of intervention approaches.

Association of Hearing Impairment With Incident Frailty and Falls in Older Adults

OBJECTIVE

We aimed to determine whether hearing impairment (HI) in older adults is associated with the development of frailty and falls.

METHOD

Longitudinal analysis of observational data from the Health, Aging and Body Composition study of 2,000 participants aged 70 to 79 was conducted. Hearing was defined by the pure-tone-average of hearing thresholds at 0.5, 1, 2, and 4 kHz in the better hearing ear. Frailty was defined as a gait speed of <0.60 m/s and/or inability to rise from a chair without using arms. Falls were assessed annually by self-report.

RESULTS

Older adults with moderate-or-greater HI had a 63% increased risk of developing frailty (adjusted hazard ratio [HR] = 1.63, 95% confidence interval [CI] = [1.26, 2.12]) compared with normal-hearing individuals. Moderate-or-greater HI was significantly associated with a greater annual percent increase in odds of falling over time (9.7%, 95% CI = [7.0, 12.4] compared with normal hearing, 4.4%, 95% CI = [2.6, 6.2]).

DISCUSSION

HI is independently associated with the risk of frailty in older adults and with greater odds of falling over time.

The Neural Consequences of Age-Related Hearing Loss

During hearing, acoustic signals travel up the ascending auditory pathway from the cochlea to auditory cortex; efferent connections provide descending feedback. In human listeners, although auditory and cognitive processing have sometimes been viewed as separate domains, a growing body of work suggests they are intimately coupled. Here, we review the effects of hearing loss on neural systems supporting spoken language comprehension, beginning with age-related physiological decline. We suggest that listeners recruit domain general executive systems to maintain successful communication when the auditory signal is degraded, but that this compensatory processing has behavioral consequences: even relatively mild levels of hearing loss can lead to cascading cognitive effects that impact perception, comprehension, and memory, leading to increased listening effort during speech comprehension.

Seeing the Talker's Face Improves Free Recall of Speech for Young Adults With Normal Hearing but Not Older Adults With Hearing Loss

PURPOSE

Seeing the talker's face improves speech understanding in noise, possibly releasing resources for cognitive processing. We investigated whether it improves free recall of spoken two-digit numbers.

METHOD

Twenty younger adults with normal hearing and 24 older adults with hearing loss listened to and subsequently recalled lists of 13 two-digit numbers, with alternating male and female talkers. Lists were presented in quiet as well as in stationary and speech-like noise at a signal-to-noise ratio giving approximately 90% intelligibility. Amplification compensated for loss of audibility.

RESULTS

Seeing the talker's face improved free recall performance for the younger but not the older group. Poorer performance in background noise was contingent on individual differences in working memory capacity. The effect of seeing the talker's face did not differ in quiet and noise.

CONCLUSIONS

We have argued that the absence of an effect of seeing the talker's face for older adults with hearing loss may be due to modulation of audiovisual integration mechanisms caused by an interaction between task demands and participant characteristics. In particular, we suggest that executive task demands and interindividual executive skills may play a key role in determining the benefit of seeing the talker's face during a speech-based cognitive task.

Effects of Aging and Adult-Onset Hearing Loss on Cortical Auditory Regions

Hearing loss is a common feature in human aging. It has been argued that dysfunctions in central processing are important contributing factors to hearing loss during older age. Aging also has well documented consequences for neural structure and function, but it is not clear how these effects interact with those that arise as a consequence of hearing loss. This paper reviews the effects of aging and adult-onset hearing loss in the structure and function of cortical auditory regions. The evidence reviewed suggests that aging and hearing loss result in atrophy of cortical auditory regions and stronger engagement of networks involved in the detection of salient events, adaptive control and re-allocation of attention. These cortical mechanisms are engaged during listening in effortful conditions in normal hearing individuals. Therefore, as a consequence of aging and hearing loss, all listening becomes effortful and cognitive load is constantly high, reducing the amount of available cognitive resources. This constant effortful listening and reduced cognitive spare capacity could be what accelerates cognitive decline in older adults with hearing loss.

Associations between the neighbourhood environment characteristics and physical activity in older adults with specific types of chronic conditions: the ALECS cross-sectional study

Background

Neighbourhood characteristics may influence physical activity (PA), which has positive effects on the health of older adults. Older adults with chronic conditions are less active and possibly more affected by environmental factors than their peers. Understanding neighbourhood characteristics associated with PA specific to older adults with chronic conditions is currently lacking. This cross-sectional study aimed to assess the associations between the neighbourhood environment and various forms of PA in older adults with and without visual impairment, hearing impairment, musculoskeletal disease and/or genitourinary disease.

Methods

Neighbourhood environment and PA data were collected in Hong Kong older adults (N = 909) from 124 preselected neighbourhoods stratified for walkability and socioeconomic status. Generalized linear models and zero-inflated negative binomial models with robust standard errors were used to examine associations of perceived neighbourhood environment characteristics, and the moderating effects of having specific chronic conditions, with PA outcomes.

Results

Thirteen perceived neighbourhood characteristics were associated with older adults’ PA in the expected direction irrespective of their health condition. Nine neighbourhood characteristics had associations with PA that were dependent on hearing impairment, vision impairment, musculoskeletal disease or genitourinary disease. In general, they were stronger in participants with than without a specific chronic condition.

Conclusions

Maximizing the potential for PA in older adults who have lower levels of physical functionality due to chronic conditions may require neighbourhood characteristics specific to these groups.

Cross-Modal Re-Organization in Clinical Populations with Hearing Loss

We review evidence for cross-modal cortical re-organization in clinical populations with hearing loss. Cross-modal plasticity refers to the ability for an intact sensory modality (e.g., vision or somatosensation) to recruit cortical brain regions from a deprived sensory modality (e.g., audition) to carry out sensory processing. We describe evidence for cross-modal changes in hearing loss across the age-spectrum and across different degrees of hearing impairment, including children with profound, bilateral deafness with cochlear implants, single-sided deafness before and after cochlear implantation, and adults with early-stage, mild-moderate, age-related hearing loss. Understanding cross-modal plasticity in the context of auditory deprivation, and the potential for reversal of these changes following intervention, may be vital in directing intervention and rehabilitation options for clinical populations with hearing loss.

Visual Cross-Modal Re-Organization in Children with Cochlear Implants

BACKGROUND

Visual cross-modal re-organization is a neurophysiological process that occurs in deafness. The intact sensory modality of vision recruits cortical areas from the deprived sensory modality of audition. Such compensatory plasticity is documented in deaf adults and animals, and is related to deficits in speech perception performance in cochlear-implanted adults. However, it is unclear whether visual cross-modal re-organization takes place in cochlear-implanted children and whether it may be a source of variability contributing to speech and language outcomes. Thus, the aim of this study was to determine if visual cross-modal re-organization occurs in cochlear-implanted children, and whether it is related to deficits in speech perception performance.

METHODS

Visual evoked potentials (VEPs) were recorded via high-density EEG in 41 normal hearing children and 14 cochlear-implanted children, aged 5-15 years, in response to apparent motion and form change. Comparisons of VEP amplitude and latency, as well as source localization results, were conducted between the groups in order to view evidence of visual cross-modal re-organization. Finally, speech perception in background noise performance was correlated to the visual response in the implanted children.

RESULTS

Distinct VEP morphological patterns were observed in both the normal hearing and cochlear-implanted children. However, the cochlear-implanted children demonstrated larger VEP amplitudes and earlier latency, concurrent with activation of right temporal cortex including auditory regions, suggestive of visual cross-modal re-organization. The VEP N1 latency was negatively related to speech perception in background noise for children with cochlear implants.

CONCLUSION

Our results are among the first to describe cross modal re-organization of auditory cortex by the visual modality in deaf children fitted with cochlear implants. Our findings suggest that, as a group, children with cochlear implants show evidence of visual cross-modal recruitment, which may be a contributing source of variability in speech perception outcomes with their implant.

Functional neuroanatomy of spatial sound processing in Alzheimer's disease

Deficits of auditory scene analysis accompany Alzheimer's disease (AD). However, the functional neuroanatomy of spatial sound processing has not been defined in AD. We addressed this using a “sparse” fMRI virtual auditory spatial paradigm in 14 patients with typical AD in relation to 16 healthy age-matched individuals. Sound stimulus sequences discretely varied perceived spatial location and pitch of the sound source in a factorial design. AD was associated with loss of differentiated cortical profiles of auditory location and pitch processing at the prescribed threshold, and significant group differences were identified for processing auditory spatial variation in posterior cingulate cortex (controls > AD) and the interaction of pitch and spatial variation in posterior insula (AD > controls). These findings build on emerging evidence for altered brain mechanisms of auditory scene analysis and suggest complex dysfunction of network hubs governing the interface of internal milieu and external environment in AD. Auditory spatial processing may be a sensitive probe of this interface and contribute to characterization of brain network failure in AD and other neurodegenerative syndromes.

How Does Auditory Training Work? Joined-Up Thinking and Listening

Auditory training aims to compensate for degradation in the auditory signal and is offered as an intervention to help alleviate the most common complaint in people with hearing loss, understanding speech in a background noise. Yet there remain many unanswered questions. This article reviews some of the key pieces of evidence that assess the evidence for whether, and how, auditory training benefits adults with hearing loss. The evidence supports that improvements occur on the trained task; however, transfer of that learning to generalized real-world benefit is much less robust. For more than a decade, there has been an increasing awareness of the role that cognition plays in listening. But more recently in the auditory training literature, there has been an increased focus on assessing how cognitive performance relevant for listening may improve with training. We argue that this is specifically the case for measures that index executive processes, such as monitoring, attention switching, and updating of working memory, all of which are required for successful listening and communication in challenging or adverse listening conditions. We propose combined auditory-cognitive training approaches, where training interventions develop cognition embedded within auditory tasks, which are most likely to offer generalized benefits to the real-world listening abilities of people with hearing loss.

Cellular signaling protective against noise-induced hearing loss – A role for novel intrinsic cochlear signaling involving corticotropin-releasing factor?

Hearing loss afflicts approximately 15% of the world's population, and crosses all socioeconomic boundaries. While great strides have been made in understanding the genetic components of syndromic and non-syndromic hearing loss, understanding of the mechanisms underlying noise-induced hearing loss (NIHL) have come much more slowly. NIHL is not simply a mechanism by which older individuals loose their hearing. Significantly, the incidence of NIHL is increasing, and is now involving ever younger populations. This may predict future increased occurrences of hearing loss. Current research has shown that even short-term exposures to loud sounds generating what was previously considered temporary hearing loss, actually produces an almost immediate and permanent loss of specific populations of auditory nerve fibers. Additionally, recurrent exposures to intense sound may hasten age-related hearing loss. While NIHL is a significant medical concern, to date, few compounds have delivered significant protection, arguing that new targets need to be identified. In this commentary, we will explore cellular signaling processes taking place in the cochlea believed to be involved in protection against hearing loss, and highlight new data suggestive of novel signaling not previously recognized as occurring in the cochlea, that is perhaps protective of hearing. This includes a recently described local hypothalamic-pituitary-adrenal axis (HPA)-like signaling system fully contained in the cochlea. This system may represent a local cellular stress-response system based on stress hormone release similar to the systemic HPA axis. Its discovery may hold hope for new drug therapies that can be delivered directly to the cochlea, circumventing systemic side effects.

Hearing Loss is Associated With Risk of Alzheimer's Disease: A Case-Control Study in Older People

Background

It remains unknown whether hearing loss increases the risk of Alzheimer’s disease. This study aimed to examine the association between hearing loss and risk of Alzheimer’s disease in older people in Taiwan.

Methods

Analyzing the database from Taiwan’s National Health Insurance Program, this case-control study enrolled 488 subjects ≥65 years old with newly diagnosed Alzheimer’s disease as a case group and 1952 subjects without Alzheimer’s disease as a control group from 1998–2011. Patients with Alzheimer’s disease and other comorbidities were identified by analyzing ICD-9 coding in claims data. The association of hearing loss, other comorbidities, and risk of Alzheimer’s disease were compared between groups.

Results

After controlling for confounders, multivariable logistic regression showed an adjusted odds ratio of Alzheimer’s disease of 1.39 in people with hearing loss (95% CI, 1.05–1.84) versus those without. Parkinson’s disease (OR 4.44; 95% CI, 2.54–7.78), head injury (OR 2.31; 95% CI, 1.46–3.66), depression (OR 1.68; 95% CI, 1.19–2.39), hypertension (OR 1.40; 95% CI, 1.10–1.79), and age (each year, OR 1.03; 95% CI, 1.01–1.05) also showed strong links with Alzheimer’s.

Conclusions

Hearing loss is associated with increased risk of Alzheimer’s disease in older people in Taiwan.

Hearing impairment and cognitive decline: a pilot study conducted within the atherosclerosis risk in communities neurocognitive study

Hearing impairment (HI) is prevalent, is modifiable, and has been associated with cognitive decline. We tested the hypothesis that audiometric HI measured in 2013 is associated with poorer cognitive function in 253 men and women from Washington County, Maryland (mean age = 76.9 years) in a pilot study carried out within the Atherosclerosis Risk in Communities Neurocognitive Study. Three cognitive tests were administered in 1990-1992, 1996-1998, and 2013, and a full neuropsychological battery was administered in 2013. Multivariable-adjusted differences in standardized cognitive scores (cross-sectional analysis) and trajectories of 20-year change (longitudinal analysis) were modeled using linear regression and generalized estimating equations, respectively. Hearing thresholds for pure tone frequencies of 0.5-4 kHz were averaged to obtain a pure tone average in the better-hearing ear. Hearing was categorized as follows: ≤25 dB, no HI; 26-40 dB, mild HI; and >40 dB, moderate/severe HI. Comparing participants with moderate/severe HI to participants with no HI, 20-year rates of decline in memory and global function differed by -0.47 standard deviations (P = 0.02) and -0.29 standard deviations (P = 0.02), respectively. Estimated declines were greatest in participants who did not wear a hearing aid. These findings add to the limited literature on cognitive impairments associated with HI, and they support future research on whether HI treatment may reduce risk of cognitive decline.

The impact of hearing loss on language performance in older adults with different stages of cognitive function

Purpose

The possible relationship between audiometric hearing thresholds and cognitive performance on language tests was analyzed in a cross-sectional cohort of older adults aged ≥65 years (N=98) with different degrees of cognitive impairment.

Materials and methods

Participants were distributed into two groups according to Reisberg’s Global Deterioration Scale (GDS): a normal/predementia group (GDS scores 1–3) and a moderate/moderately severe dementia group (GDS scores 4 and 5). Hearing loss (pure-tone audiometry) and receptive and production-based language function (Verbal Fluency Test, Boston Naming Test, and Token Test) were assessed.

Results

Results showed that the dementia group achieved significantly lower scores than the predementia group in all language tests. A moderate negative correlation between hearing loss and verbal comprehension (r=−0.298; P<0.003) was observed in the predementia group (r=−0.363; P<0.007). However, no significant relationship between hearing loss and verbal fluency and naming scores was observed, regardless of cognitive impairment.

Conclusion

In the predementia group, reduced hearing level partially explains comprehension performance but not language production. In the dementia group, hearing loss cannot be considered as an explanatory factor of poor receptive and production-based language performance. These results are suggestive of cognitive rather than simply auditory problems to explain the language impairment in the elderly.

Aging, cognitive load, dementia and hearing loss

Sensorineural systems play a crucial role in the diagnosis, treatment and management of several neurological disorders. The function of the eye and ear represents a unique window for testing various conditions in cognitive decline or dementia. Touch and smell have also been found to be strongly involved in neurodegenerative conditions, and their decline has been significantly associated with the progression of the disease; hence, the idea that restoring sensory function in cognitively impaired adults might enable a significant improvement in their cognitive status, reducing the worldwide incidence and prevalence of dementia. Not all sensorineural 'windows' can benefit equally from the same procedures; however, hearing and vision can certainly gain the most from dependable therapeutic and other diagnostic options. The ear, including the vestibular system, deserves an honored place among the sensory organs in this context due mainly to the sophisticated electrical devices available that have amply demonstrated their effectiveness in treating hearing loss. Restoring an individual's hearing can reduce the cognitive 'load', i.e. the neural activity needed to understand/recognize the spoken word - an activity that becomes more demanding if the brain is obliged to recruit different neural populations to achieve the same performance, as happens in older adults with sensory impairments. The sensory interfaces may also facilitate the early diagnosis of conditions characterized by a lengthy preclinical phase, as well as enabling noninvasive, follow-up procedures to assess the outcome of rehabilitation measures and distinguish physiological brain aging from neurodegenerative disorders. The present study is a brief literature review on the issues and prospects relating to the unique relationship between hearing and cognitive decline, with a general introduction to the main topics before focusing on rehabilitation training with hearing aids and cochlear implants to combat cognitive decline.

The effect of functional hearing loss and age on long- and short-term visuospatial memory: evidence from the UK biobank resource

The UK Biobank offers cross-sectional epidemiological data collected on >500,000 individuals in the UK between 40 and 70 years of age. Using the UK Biobank data, the aim of this study was to investigate the effects of functional hearing loss and hearing aid usage on visuospatial memory function. This selection of variables resulted in a sub-sample of 138,098 participants after discarding extreme values. A digit triplets functional hearing test was used to divide the participants into three groups: poor, insufficient and normal hearers. We found negative relationships between functional hearing loss and both visuospatial working memory (i.e., a card pair matching task) and visuospatial, episodic long-term memory (i.e., a prospective memory task), with the strongest association for episodic long-term memory. The use of hearing aids showed a small positive effect for working memory performance for the poor hearers, but did not have any influence on episodic long-term memory. Age also showed strong main effects for both memory tasks and interacted with gender and education for the long-term memory task. Broader theoretical implications based on a memory systems approach will be discussed and compared to theoretical alternatives.

Hearing loss and cognitive decline in older adults: questions and answers

The association between hearing impairment, the diagnosis of dementia, and the role of sensory therapy has been proposed for some time, but further research is needed. Current understanding of this association requires the commitment of those experts who can integrate experience and research from several fields to be able to understand the link from hearing to dementia. A workshop whose panelists included experts from many areas, ranging from ear, nose and throat (ENT) to dementia's specialists, was promoted and organized by the Giovanni Lorenzini Medical Science Foundation (Milan, Italy; Houston, TX, USA) to increase the awareness of the relationship between hearing loss and dementia, and included questions and comments following a presentation from the clinical researcher, Frank Lin, who has been evaluating the relationship between hearing loss and cognitive decline since 2009.

Changes in the default mode networks of individuals with long-term unilateral sensorineural hearing loss

Hearing impairment contributes to cognitive dysfunction. Previous studies have found changes of functional connectivity in the default mode network (DMN) associated with cognitive processing in individuals with sensorineural hearing loss (SNHL). Whereas the changes in the DMN in patients with long-term unilateral SNHL (USNHL) is still not entirely clear. In this work, we analyzed resting-state functional magnetic resonance imaging (fMRI) data and neuropsychological test scores from normal hearing subjects (n = 11) and patients (n = 21) with long-term USNHL. Functional connectivity and nodal topological properties were computed for every brain region in the DMN. Analysis of covariance (ANCOVA) and post hoc analyses were conducted to identify differences between normal controls and patients for each measure. Results indicated that the left USNHL presented enhanced connectivity (p < 0.05, false discovery rate (FDR) corrected), and significant changes (p < 0.05, Bonferroni corrected) of the nodal topological properties in the DMN compared with the control. More changes in the DMN have been found in the left than right long-term USNHL (RUSNHL). However, the neuropsychological tests did not show significant differences between the USNHL and the control. These findings suggest that long-term USNHL contributes to changes in the DMN, and these changes might affect cognitive abilities in patients with long-term USNHL. Left hearing loss affects the DMN more than the right hearing loss does. The fMRI measures might be more sensitive for observing cognitive changes in patients with hearing loss than clinical neuropsychological tests. This study provides some insights into the mechanisms of the association between hearing loss and cognitive function.

Age-related changes in the subcortical-cortical encoding and categorical perception of speech

Aging is associated with declines in auditory processing including speech comprehension abilities. Here, we evaluated both brainstem and cortical speech-evoked brain responses to elucidate how aging impacts the neural transcription and transfer of speech information between functional levels of the auditory nervous system. Behaviorally, older adults showed slower, more variable speech classification performance than younger listeners, which coincided with reduced brainstem amplitude and increased, but delayed, cortical speech-evoked responses. Mild age-related hearing loss showed differential correspondence with neurophysiological responses showing negative (brainstem) and positive (cortical) correlations with brain activity. Spontaneous brain activity, that is, "neural noise," did not differ between older and younger adults. Yet, mutual information and correlations computed between brainstem and cortex revealed higher redundancy (i.e., lower interdependence) in speech information transferred along the auditory pathway implying less neural flexibility in older adults. Results are consistent with the notion that weakened speech encoding in brainstem is overcompensated by increased cortical dysinhibition in the aging brain. Findings suggest aging negatively impacts speech listening abilities by distorting the hierarchy of speech representations, reducing neural flexibility through increased neural redundancy, and ultimately impairing the acoustic-phonetic mapping necessary for robust speech understanding.