Relationship between tinnitus and olfactory dysfunction: audiovisual, olfactory, and medical examinations.

Introduction: Sensory dysfunctions and cognitive impairments are related to each other. Although a relationship between tinnitus and subjective olfactory dysfunction has been reported, there have been no reports investigating the relationship between tinnitus and olfactory test results. Methods: To investigate the relationship between tinnitus and olfactory test results, we conducted sensory tests, including hearing and visual examinations. The subjects included 510 community-dwelling individuals (295 women and 215 men) who attended a health checkup in Yakumo, Japan. The age of the subjects ranged from 40 to 91 years (mean ± standard deviation, 63.8 ± 9.9 years). The participants completed a self-reported questionnaire on subjective tinnitus, olfactory function, and hearing function, as well as their lifestyle. The health checkup included smell, hearing, vision, and blood examinations. Results: After adjusting for age and sex, the presence of tinnitus was significantly associated with subjective olfactory dysfunction, poor olfactory test results, hearing deterioration, vertigo, and headache. Additionally, high serum calcium levels and a low albumin/globulin ratio were significantly associated with low physical activity and nutrition. Women scored higher than men in olfactory and hearing examinations, but there was no gender difference in vision examinations. Conclusion: Subjective smell dysfunction and poor smell test results were significantly associated with tinnitus complaints. Hearing and vision were associated even after adjusting for age and sex. These findings suggest that evaluating the mutual relationships among sensory organs is important when evaluating the influence of sensory dysfunctions on cognitive function.

The association of food intake on the development of hearing impairment after middle age among Japanese community dwellers.

OBJECTIVES: This study aimed to determine whether food intake modifies the risk of developing hearing impairment (HI) in Japanese adults in their 40s. METHODS: Data for individuals who were in their 40s with no HI at baseline and had participated in the survey multiple times were extracted from the National Institute for Longevity Sciences, Longitudinal Study of Aging. A total of 1846 samples observed for up to 11.5 years in 421 participants were included in the analyses. The average 3-day food intake was calculated. HI is defined as a pure-tone average of the better ear at frequencies of 0.5, 1, 2, and 4 kHz greater than 25 dB. The risk of developing HI in the 18 food groups was calculated longitudinally using multivariable cumulative data analyses. RESULTS: Even after adjusting basic confounding factors, food groups, and baseline hearing level, significant associations were found between beverage consumption and risk increments for HI (odds ratio [OR] = 2.374, 95% confidence interval [CI]:1.141-4.940) and also between mushroom intake and risk reduction (OR = 0.215, 95% CI:0.069-0.667). Other foods did not consistently show significant results when the combination of analysis variables were changed. CONCLUSIONS: Although the effect of food on hearing is modest to the extent that the significance varies with the variables used in the analysis, the intake of beverages and mushrooms could potentially modify the risk of developing HI after middle age.

Relationship between cognitive domains and hearing ability in memory clinic patients: How did the relationship change after 6 months of introducing a hearing aid?

OBJECTIVE: We aimed to evaluate the relationship between hearing ability and cognitive domains and determine how the relationship changes after 6 months of introducing a hearing aid. METHODS: We conducted a 6-month hearing aid lending study between September 2014 and March 2019, including 59 older participants who visited the Memory Clinic at the National Center for Geriatrics and Gerontology. The hearing level was assessed using pure tone audiometry. Speech intelligibility was measured using the monosyllabic word discrimination score. We assessed the relationship between hearing ability and cognitive domains using the Mini-Mental State Examination (MMSE) total score and four subscale scores (orientation, memory, attention, and language). Differences in the cognitive function between baseline (pre-) and 6 months later (post-) after introducing a hearing aid were also assessed. RESULTS: The pre-orientation score was significantly associated with the pure-tone average (p = 0.013), and the pre-language score was significantly associated with speech intelligibility (p = 0.006) after adjusting for confounders. None of the MMSE subscale scores were significantly different between pre- and post-scores, however, an expectation of improvement with continuous hearing aid use was implied in the attention domain. CONCLUSION: We found a significant association between hearing ability and cognitive domains in individuals whose cognitive functions were not considered healthy. The presence of a potential relationship between cognitive domains, hearing ability, and auditory compensation is suggested.

Cognitive impairment is correlated with olfactory identification deficits in older Japanese adults: A cross-sectional study using objective and subjective olfactory measures.

AIM: Olfactory impairment is associated with cognitive impairment. However, differences between subjective and objective olfactory impairment measurements in older adults and their relationship with cognitive impairment are unclear. METHODS: We assessed the relationship between cognitive and olfactory impairments via a single-center observational study in 2020. Forty-seven individuals who visited our memory clinic were enrolled and asked to complete objective and subjective olfactory tests. Participants had dementia, mild cognitive impairment, or normal cognition. We administered the Open Essence (a simple card-type odor identification test) and self-administered odor questionnaire to assess objective and subjective olfaction, respectively, and the Mini-Mental State Examination to assess cognitive function. RESULTS: Older age was related to decreased Open Essence scores (P < 0.001). Compared with the mild cognitive impairment and normal cognition groups, the dementia group had significantly lower Open Essence scores (P < 0.001). Cognitive impairment was also associated with decreased Open Essence scores after adjusting for age, sex, and education (P < 0.001). Participants with dementia did not obtain lower self-administered odor questionnaire scores than those with normal cognition, and they tended to be unaware of their olfactory impairment. CONCLUSION: Open Essence scores significantly decreased according to the degree of cognitive impairment. Participants with dementia were unaware of their olfactory impairment, as indicated by odor questionnaire scores. Objective and subjective scores of olfaction differed in participants with dementia. Concomitant assessment of objective and subjective olfaction is useful to screen older adults with both olfactory and cognitive impairments. Geriatr Gerontol Int 2022; 22: 924-929.

Prevalence of usage of hearing aids and its association with cognitive impairment in Japanese community-dwelling elders with hearing loss.

OBJECTIVE: Hearing loss is a risk factor for cognitive impairment, and the use of a hearing aid (HA) may prevent cognitive decline alongside hearing loss. We aimed to elucidate the prevalence of self-reported HA usage in Japanese community-dwelling elders with hearing loss, and the effect of hearing and HA on cognitive impairment. METHODS: A total of 1193 participants, who had audiometric defined hearing loss and were aged 60 years or over, had their cumulative 3260 observations followed up for 10 years from a large cohort of a Japanese study. Association between hearing (pure-tone average threshold level at 500, 1000, 2000, and 4000 Hz from the better hearing ear: PTABHE) and HA usage with cognitive impairment (total score of Mini-Mental State Estimation was under 27 or diagnosed as dementia) was analyzed using generalized estimating equations. RESULTS: The HA usage rate of the 1193 community-dwelling elders with hearing loss was 6% during the first involvement. The majority (59.2%) of HA users always used an HA. HA usage rate was 0.7% for the mild hearing loss group and 32.4% for the moderate or greater hearing loss group in the latest participating wave. PTABHE was significantly associated with cognitive impairment (odds ratio for every 10 dB 1.36; 95% CI 1.21-1.53, p<0.0001) after adjusting for age, sex, education, depressed mood, smoking status, alcohol intake, income, activity, obesity, histories of hypertension, dyslipidemia, ischemic heart disease, diabetes, stroke, ear disease, and occupational noise exposure. PTABHE was also significantly associated with cognitive impairment in the mild hearing loss group (odds ratio for every 10 dB 1.34; 95% CI 1.05-1.72, p = 0.020) and moderate hearing loss group (odds ratio for every 10 dB 1.82; 95% CI 1.27-2.61, p = 0.001). HA use showed a significant suppressive effect on cognitive impairment in those with moderate hearing loss who always use an HA (odds ratio 0.54; 95% CI 0.30-1.00, p = 0.049). CONCLUSION: The prevalence of HA usage among Japanese community-dwelling elders with hearing loss is consistent, at around 10%. The hearing level remained a primary risk factor for cognitive impairment among elders with hearing loss after adjusting for several confounding factors. Regular HA use may have a protective effect on cognitive impairment in those with moderate hearing loss.

Longitudinal associations between hearing aid usage and cognition in community-dwelling Japanese older adults with moderate hearing loss.

We investigated the associations between hearing aids (HA) and the maintenance of cognitive function among community-dwelling older adults with moderate hearing loss. A total of 407 participants aged 60 years or older with moderate hearing loss were recruited from the National Institute for Longevity Sciences, Longitudinal Study for Aging (NILS-LSA). Moderate hearing loss was defined as a pure-tone average of 40-69 dB at 500, 1000, 2000, and 4000 Hz of the better ear, according to the definition proposed by the Japan Audiological Society. Cognitive function was evaluated using the four subtests of the Japanese version of the Wechsler Adult Intelligence Scale-Revised Short Forms (WAIS-R-SF): Information, Similarities, Picture completion, and Digit Symbol Substitution (DSST). A longitudinal analysis of 1192 observations with a mean follow-up period of 4.5 ± 3.9 years was performed. The HA use rate at any time during the follow-up period was 31.4%, and HA users were significantly younger (t-test, p = 0.001), had worse hearing (p < .0001) and higher education (p = 0.001), participated more frequently in the survey (p < .0001), and were less depressed (χ2 test, p = 0.003) than the older adults not using HA. General linear mixed models consisted of the fixed effects of HA use, follow-up time, and an HA use × time interaction term adjusted for age and pure-tone average thresholds at baseline, sex, education, and other possible confounders. HA use showed significant main effects on the scores for Picture completion and DSST after adjustment; scores were better in the HA use group than in the no HA use group. The HA use × time interaction was significant for the Information score (p = 0.040). The model-predicted 12-year slope with centralizing age indicated that the no HA use group showed greater decline over time on Information scores than did HA use group. The slopes did not differ between HA users and non-users for the Similarities, Picture completion and DSST. In conclusion, HA use may have a protective effect on the decline in general knowledge in older adults with moderate hearing loss.

A Multi-Institutional Study of Older Hearing Aids Beginners-A Prospective Single-Arm Observation on Executive Function and Social Interaction.

OBJECTIVES: To obtain new insights into research questions on how executive function and social interaction would be observed to change after the introduction of hearing aids (HAs) in older people with hearing impairment. DESIGN: Multi-institutional prospective single-arm observational study. SETTING AND PARTICIPANTS: Outpatients with complaints of hearing difficulty who visited HA clinics between October 18, 2017, and June 30, 2019, in 7 different university hospitals in Japan. METHODS: The inclusion criteria of the study named Hearing-Aid Introduction for Hearing-Impaired Seniors to Realize a Productive Aging Society-A Study Focusing on Executive Function and Social Activities Study (HA-ProA study) were age ≥60 years and no history of HA use. A series of multi-institution common evaluations including audiometric measurements, the digit symbol substitution test to assess executive functions, convoy model as an index of social relations, and hearing handicap inventory for the elderly (HHIE) were performed before (pre-HA) and after 6 months of the HA introduction (post-HA). RESULTS: Out of 127 enrollments, 94 participants completed a 6-month follow-up, with a mean age of 76.9 years. The digit symbol substitution test score improved significantly from 44.7 at baseline to 46.1 at 6 months (P = .0106). In the convoy model, the social network size indicated by the number of persons in each and whole circles were not significantly different between pre- and post-HA; however, the total count for kin was significantly increased (P = .0344). In the analyses of HHIE, the items regarding the family and relatives showed significant improvement. CONCLUSIONS AND IMPLICATIONS: HA use could benefit older individuals beginning to use HAs in executive function and social interaction, though the results should be interpreted cautiously given methodological limitations such as a single-arm short 6 months observation. Reduction in daily hearing impairment would have a favorable effect on relationships with the family.

Association of Matrix Metalloproteinase-2 mRNA Expression with Subtypes of Pediatric Cholesteatoma.

OBJECTIVE: Cholesteatoma is a clinically heterogeneous disease, with some patients showing spontaneous regression, while others experiencing an aggressive, lethal disease. Cholesteatoma in children can be divided into two types: congenital and acquired. Identifying good prognostic markers is needed to help select patients who will require immediate surgical intervention. Matrix metalloproteinase-2 (MMP2) was previously reported to play an important role in cholesteatoma progression, by promoting bone destruction and keratinocyte infiltration. Herein, we analyzed MMP2 mRNA expression level in cholesteatoma using RNA-in situ hybridization in formalin-fixed, paraffin-embedded (FFPE) tissue samples. METHODS: Sixty patients with cholesteatoma under 15 years old, who underwent their primary surgery at Aichi Medical University's Otolaryngology Department, were analyzed for MMP2 expression level, using RNA-in situ hybridization. RESULTS: There were no significant differences in MMP2 mRNA expression level between congenital cholesteatoma and acquired cholesteatomas. In congenital cholesteatoma, higher MMP2 signals were observed in the open type than in the closed type (p < 0.001). In acquired cholesteatoma, higher MMP2 signals were observed in the pars tensa than in the pars flaccida (p < 0.001). MMP2 mRNA expression level was almost exclusively found in the fibroblasts or in the inflammatory cells in the stroma, but not in the epithelium. CONCLUSION: Our study reveals that MMP2 mRNA expression level is strongly associated with the subtypes of cholesteatoma. The findings suggest that the level of expression of MMP2 mRNA may be related to the pathogenesis and aggressive features of cholesteatoma.

Imaging of endolymphatic hydrops on a vertigo attack of Meniere's disease.

Meniere's disease (MD) characteristically presents with endolymphatic hydrops (EH), which can be visualized with gadolinium-enhanced inner ear magnetic resonance imaging (MRI). Inner ear membrane rupture has been suspected to cause MD attacks, but this remains controversial. We report a case of MD coincidentally evaluated the EH using 3-Tesla MRI during a vertigo attack. A 78-year-old man with bilateral definite MD visited the hospital outpatient department due to a vertigo attack. To evaluate of endolymphatic hydrops on the attack, inner ear MRI was obtained 4 hours after intravenous injection of gadolinium agent. Vestibular EH in each ear occupied almost all vestibular endolymphatic space in contact with the oval window and herniated into the horizontal semi-circular canal. The endolymphatic space was enlarged, without collapse or mixture of contrast agent. No difference was found between ears. EH on a vertigo attack was associated with significant swelling, without obvious evidence of membranous ruptures on magnetic resonance images.

Aging Brain and Hearing: A Mini-Review.

Brain reserve is a topic of great interest to researchers in aging medicine field. Some individuals retain well-preserved cognitive function until they fulfill their lives despite significant brain pathology. One concept that explains this paradox is the reserve hypothesis, including brain reserve that assumes a virtual ability to mitigate the effects of neuropathological changes and reduce the effects on clinical symptoms flexibly and efficiently by making complete use of the cognitive and compensatory processes. One of the surrogate measures of reserve capacity is brain volume. Evidence that dementia and hearing loss are interrelated has been steadily accumulating, and age-related hearing loss is one of the most promising modifiable risk factors of dementia. Research focused on the imaging analysis of the aged brain relative to auditory function has been gradually increasing. Several morphological studies have been conducted to understand the relationship between hearing loss and brain volume. In this mini review, we provide a brief overview of the concept of brain reserve, followed by a small review of studies addressing brain morphology and hearing loss/hearing compensation, including the findings obtained from our previous study that hearing loss after middle age could affect hippocampal and primary auditory cortex atrophy.

Hearing impairment is associated with cognitive function in community-dwelling older adults: A cross-sectional study.

BACKGROUND: Hearing impairment (HI) is associated with dementia. However, the cognitive screening tasks effective in older community dwellers presenting with HI are unclear. METHODS: We retrospectively and cross-sectionally investigated the associations between HI and cognitive function assessed with screening tasks using data from two healthcare check-up programs for community dwellers ≥65 years old in 2018. We examined demographics, risk factors, cognitive function, hearing condition, lifestyles, and self-care levels. Cognitive function was assessed using the clock drawing task and the delayed three words recall task. Hearing condition was assessed using questionnaires on the use of hearing aids and HI during conversation situations. Multivariate analysis was used to identify independent associations between HI and cognitive assessment tasks. RESULTS: We analyzed 1602 eligible participants (61.9% women; 74.3 ± 6.5 years old). Hearing aid users (n = 90) were older (80 vs. 73 years, respectively; p < 0.001) and less likely to draw the clock correctly (71.1% vs. 80.1% years, respectively; p = 0.044) than non-hearing aid users. Multivariate logistic regression analysis showed that HI was associated with inability to draw the clock correctly (odds ratio 1.60, 95% confidence interval 1.12-2.26; p = 0.011), independent of age, living alone, memory impairment, and impaired self-care levels. CONCLUSION: Hearing impairment is independently associated with cognitive decline assessed by the clock drawing task. The clock drawing task may be useful for identifying an increased risk of dementia in older subjects presenting with HI.

Availability of audiological evaluation for the differential diagnosis of clinical otosclerosis.

OBJECTIVE: The availability of an audiological evaluation for the differential diagnosis of clinical otosclerosis (OS) was examined. METHODS: Included were 98 patients (107 ears) with OS and 19 patients (20 ears) with incudostapedial disconnection (ISD) diagnosed by surgery between 2009 and 2017 at Aichi University Hospital. Results of preoperative pure-tone audiometry and impedance audiometry were analyzed. The most reliable index for distinguishing the two diseases was evaluated, and the cut-off value, sensitivity, and specificity were calculated. RESULTS: In the univariate analysis, age, static compliance, reversed ipsilateral acoustic reflex (reversed IAR) at 0.5 kHz and 2 kHz, negative contralateral acoustic reflex (negative CAR), difference between the air-bone gap at 0.25 and 2 kHz (0.25-2 kHzABG) and that at 0.25 and 4 kHz (0.25-4 kHzABG) showed statistical significance between the two diseases, whereas the Carhart notch did not. Multivariate logistic regression analysis by the variable selection method showed that reversed IAR (0.5 kHz), negative CAR, and 0.25-4 kHzABG were statistically significantly better factors for the differential diagnosis of the two diseases. The receiver operating characteristic curve for diagnosing OS using the difference between air-bone gap at 0.25 kHz and 4 kHz showed moderate accuracy. If the cut-off value of 0.25-4 kHzABG was 10 dB, then the sensitivity and specificity were 81.1% and 55.0%, respectively. In other words, if the cut-off value of 0.25-4 kHzABG was less than 10 dB, then the possibility of diagnosing ISD becomes higher, and if greater than 10 dB, then the possibility of diagnosing OS becomes higher. CONCLUSION: The differences in the air-bone gap at low and high frequency in pure-tone audiometry, static compliance, and acoustic reflex in impedance audiometry are useful for distinguishing OS from ISD. However, combinations of several examinations including computed tomography imaging are needed for the differential diagnosis of other ear diseases and specific preoperative planning.

Clinical feasibility of auditory processing tests in Japanese older adults: a pilot study.

Background: Difficulty in listening comprehension is a major audiological complaint of older adults. Behavioural auditory processing tests (APTs) may evaluate it. Aims/Objectives: The aim was to assess the feasibility of administering Japanese APTs to older adults at otolaryngology clinics. Material and Methods: Using computer programs interfaced with an audiometer, APTs (dichotic listening test; fast speech test, FST; gap detection test, GDT; speech in noise test; rapidly alternating speech perception test) were administered to 20 older adults (65-84 years old; mean 75.3 years) and 20 young adults at the 40 dB sensation level. Monosyllable speech perception (MSP) and the Mini-Mental State Examination (MMSE) were evaluated. Results: APT results except for GDT were significantly correlated with MSP. The performance on each APT was worse in older adults than in young adults (p < .01). The older adults with good MSP ≥ 80% (n = 13) or excellent cognitive function (MMSE ≥ 28; n = 11) also did worse on APTs (p < .05). A ceiling effect was noted in the APT data, with FST showing a minimum ceiling effect and reflecting interindividual variations of data. Conclusions and Significance: It is feasible to administer APTs to older adults who visit otolaryngology clinics. Among our Japanese APTs, FST may be suitable for further large-scale clinical studies.

Visual changes after transnasal endoscopic versus transcaruncular medial orbital wall decompression for dysthyroid optic neuropathy.

OBJECTIVE: To compare postoperative changes in visual acuity between the transnasal endoscopic approach and the transcaruncular approach when comparison of preoperative values used for medial orbital wall decompression in patients with dysthyroid optic neuropathy. METHODS: We included 14 patients (23 sides) and divided them into a transnasal group (11 sides, 8 patients) and a transcaruncular group (12 sides, 6 patients). Visual acuity was examined preoperatively, on postoperative days 1, 3, and 7, and at a final follow-up visit. The differences in postoperative improvement of the logarithm of the minimum angle of resolution (logMAR) visual acuity and critical flicker frequency (CFF) between the two surgical groups at each time point were analyzed using the Mann-Whitney U test. RESULTS: Postoperative improvement in logMAR visual acuity on postoperative days 1 and 3 and that in CFF on postoperative day 1 were greater in the endonasal group than in the transcaruncular group (P < 0.050). Vision was improved or maintained in all patients in the transnasal group at the final follow-up. One patient in the transcaruncular group had loss of vision on one side and decreased vision on the other side after surgery. CONCLUSION: Medial orbital decompression appears to provide better postoperative vision when performed by the transnasal approach than by the transcaruncular approach in patients with dysthyroid optic neuropathy.

Hearing-impaired elderly people have smaller social networks: A population-based aging study.

BACKGROUND AND OBJECTIVES: Hearing impairment (HI) is a major global health concern. In addition, social networks are important for healthy aging. This study aimed to examine the association between HI and social relationships. RESEARCH DESIGN AND METHODS: This study was conducted by the National Institute for Longevity Sciences as part of its Longitudinal Study of Aging with 1176 Japanese participants aged 60 years or older (mean age 71.0 ± 7.4). The convoy model was used to evaluate participants' network size. A pure-tone average hearing level (HL) of 0.5, 1, 2, and 4 kHz in the better ear >25 dB HL was defined as HI. Multivariate analysis was performed to assess the relationship between HI and the network size, adjusting for age, gender, years of education, presence of depressive symptoms, and higher-level functional capacity score. RESULTS: The mean network sizes across the three circles of the convoy model differed significantly by HI status (18.7 ± 0.4 in the no-HI group vs 17.0 ± 0.5 in the HI group, p = 0.003). In particular, the number of non-kin in the outer circle was significantly less in the HI group (4.1 ± 0.2 vs 3.3 ± 0.3, p = 0.004). DISCUSSION AND IMPLICATIONS: The social network size was significantly smaller in the HI group. The outer circle of people to whom the individual feels less close and the number of non-kin were related to the presence of HI. Therefore, HI may be associated with elderly people's social relationships.

Difference in Serum Levels of Vitamin D Between Canalolithiasis and Cupulolithiasis of the Horizontal Semicircular Canal in Benign Paroxysmal Positional Vertigo.

Background and Purpose: In the horizontal canal benign paroxysmal positional vertigo (BPPV), cupulolithiasis shows apogeotropic direction changing nystagmus lasting more than 1 min, while canalolithiasis leads to geotropic direction changing nystagmus lasting < 1 min. The difference between cupulolithiasis and canalolithiasis is widely accepted to be the attachment of the displaced otoconia to the cupula of a semicircular canal. Several studies have shown a relationship between BPPV and vitamin D deficiency, but no studies have compared serum levels of vitamin D between canalolithiasis and cupulolithiasis patients. The purpose of this study was to clarify the difference in vitamin D serum level between canalolithiasis and cupulolithiasis of the horizontal canal. Methods: This retrospective study included 20 and 15 patients with canalolithiasis and cupulolithiasis of the horizontal canal, respectively. Serum levels of 25-hydroxyvitamin D [25(OH)D] during the acute phase of BPPV were measured. Results: The mean 25(OH)D serum level in patients with canalolithiasis and cupulolithiasis was 13.2 ± 1.4 and 20.4 ± 1.6 ng/mL, respectively, and the difference was statistically significant (p = 0.0014), also after adjusting for age and sex (p = 0.0351). Eighteen out of 20 (90%) and 5 of 15 (33%) patients were diagnosed with vitamin D deficiency in the canalolithiasis and cupulolithiasis groups, respectively, and this difference was also statistically significant (p = 0.0005). Conclusion: We found that serum vitamin D level in patients with canalolithiasis was significantly lower than that in patients with cupulolithiasis of the horizontal canal.

Age-related hearing loss and cognitive decline - The potential mechanisms linking the two.

The amount of attention to age-related hearing loss (ARHL) has been growing, not only from the perspective of being one of the most common health conditions affecting older adults, but also from the perspective of its relation to cognition. Results from a number of epidemiological and laboratory studies have demonstrated a significant link between ARHL and cognitive decline. The Lancet International Commission on Dementia, Prevention, Intervention, and Care has estimated that mid-life hearing loss, if eliminated, might decrease the risk of dementia by nine percent, since hearing loss is a modifiable age-associated condition linked to dementia. Despite numerous research efforts, elucidation of the underlying causal relationships between auditory and cognitive decline has not yet reached a consensus. In this review article, we focused on the hypotheses of etiological mechanisms between ARHL and cognitive decline: (1) cognitive load hypothesis; (2) common cause hypothesis; (3) cascade hypothesis; and (4) overdiagnosis or harbinger hypothesis. Factual evidence obtained in previous studies was assessed to understand the link between ARHL and cognitive decline or dementia. Additionally, an overview of the conceivable effects of hearing intervention, e.g., hearing aids and cochlear implants, on cognition were presented, and the role of hearing aid use was considered for the relevant hypotheses. We should continue to strive for social enlightenment towards the importance of 'hearing well', and cultivate a necessity for hearing screening among patients at risk of cognitive decline.

Smaller Hippocampal Volume and Degraded Peripheral Hearing Among Japanese Community Dwellers.

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