Association of sudden sensorineural hearing loss with dementia: a nationwide cohort study

Adult-onset hearing loss and incident cognitive impairment and dementia - A systematic review and meta-analysis of cohort studies

BACKGROUND

We comprehensively summarized the cohort evidence to date on adult-onset hearing loss as risk factor for incident cognitive impairment and dementia, and examined the evidence for dose-response, risk for various dementia subtypes, and other moderators. Previous meta-analyses were less comprehensive.

METHODS

We included cohort studies with participants without dementia and with hearing assessments at baseline, minimum 2 years follow-up and incident cognitive outcomes. We used random-effect models and subgroup and meta-regression on moderator analyses.

RESULTS

We identified fifty studies (N=1,548,754). Hearing loss (yes/no) was associated with incident dementia risk (HR=1.35 [95% CI = 1.26 - 1.45), mild cognitive impairment (MCI HR=1.29 [95% CI = 1.11 - 1.50]), cognitive decline not specified as MCI or dementia (HR=1.29 [95% CI = 1.17 - 1.42]), and Alzheimer's disease dementia (ADD, HR=1.56 [95% CI = 1.30 - 1.87]), but not with vascular dementia (HR, 1.30 [95% CI = 0.83 - 2.05]). Each 10-decibel worsening of hearing was associated with a 16% increase in dementia risk (95% CI = 1.07 - 1.27). The effect of hearing loss did not vary across potential moderators.

CONCLUSIONS

Cohort studies consistently support that adult-onset hearing loss increases the risk of incident cognitive decline, dementia, MCI, and ADD.

Moderating Role of Neighborhood Environment in the Associations Between Hearing Loss and Cognitive Challenges Among Older Adults: Evidence From US National Study

This study examined the associations between hearing loss and cognitive challenges among community-dwelling older adults and whether neighborhood characteristics (physical disorder and low social cohesion) moderated the associations. Cross-sectional national data from Round 11 of the National Health and Aging Trends Study were adopted (N = 2,515). Multinomial logistic regressions were used to examine associations among variables and interactive analyses were conducted to examine moderating effects. Results indicated significant relationships between the experience of hearing loss and possible dementia and between severe or profound hearing loss and probable dementia. Interactive models suggested that residing in neighborhoods with physical disorder and low social cohesion were negatively associated with possible dementia among older adults with moderate and severe or profound hearing loss, respectively, compared to those without hearing loss. Findings underscore the necessity of environmental and social interventions to enhance cognitive health among older adults with varying degrees of hearing challenges.

A case for seeking sex-specific treatments in Alzheimer's disease

There is no satisfactory explanation for the sex-related differences in the incidence of many diseases and this is also true of Alzheimer's disease (AD), where females have a higher lifetime risk of developing the disease and make up about two thirds of the AD patient population. The importance of understanding the cause(s) that account for this disproportionate distribution cannot be overestimated, and is likely to be a significant factor in the search for therapeutic strategies that will combat the disease and, furthermore, potentially point to a sex-targeted approach to treatment. This review considers the literature in the context of what is known about the impact of sex on processes targeted by drugs that are in clinical trial for AD, and existing knowledge on differing responses of males and females to these drugs. Current knowledge strongly supports the view that trials should make assessing sex-related difference in responses a priority with a focus on exploring the sex-stratified treatments.

The association of genetic polymorphisms in protocadherin 15 with sudden sensorineural hearing loss in a Chinese population

BACKGROUND

Sudden sensorineural hearing loss (SSNHL) is a multifactorial disease, and its etiology is still unknown. SSNHL may be caused by environmental factors and genetic changes. PCDH15 is associated with susceptibility to hearing loss. The relationship between PCDH15 and SSNHL remains unknown.

METHODS

In this study, the potential association between PCDH15 polymorphism and SSNHL in Chinese population was evaluated. Two single nucleotide polymorphisms PCDH15-rs7095441 and rs11004085 in 195 SSNHL patients and 182 healthy controls were determined by TaqMan technology.

RESULTS

In Chinese population, the TT genotype and T allele of rs7095441 are associated with increased susceptibility to SSNHL. The relationships between rs7095441 and the degree of hearing loss were analyzed, and TT genotype increased the risk of hearing loss. Among SSNHL patients, patients with TT genotype of rs7095441 have an increased risk of vertigo.

CONCLUSION

This study found that the TT genotype of SNP rs7095441 can increase the risk of SSNHL in Chinese population.

Correlation study of FGF23/D-serine in maintenance hemodialysis patients with combined hearing impairment

BACKGROUND

Recent studies have reported an association between chronic renal failure and hearing impairment. Yet, the exact mechanism of action is still not fully understood. In this study, we investigated the expression of fibroblast growth factor 23 (FGF23) and D-serine in maintenance hemodialysis (MHD) patients with end-stage renal disease (ESRD) complicated with hearing impairment and further investigated the correlation between FGF23/D-serine and hearing impairment.

METHODS

A total of 90 subjects, including 30 MHD patients complicated with hearing impairment, 30 MHD patients with normal hearing, and 30 controls, were included in this case-control study. Relevant data were obtained by questionnaire survey, audiometric test, enzyme-linked immunosorbent assay (ELISA) to determine FGF23 level, and high-performance liquid chromatography to determine D-serine level.

RESULTS

MHD patients showed abnormally high expression of FGF23 and D-serine, where FGF23 and D-serine levels were significantly higher in the group with hearing impairment than in the group with normal hearing and normal controls (all P<0.01). Also, elevated FGF23 and D-serine were identified as risk factors for hearing impairment in ESRD, with ORs of 16.54 (95%CI, 2.75-99.55) and 15.22 (95%CI, 2.59-89.51), respectively. Further Person correlation analysis showed a moderate positive correlation between FGF23 and D-serine (r = 0.683, P<0.001).

CONCLUSION

This study provides potential biomarkers for the early detection of hearing impairment complicated by chronic renal failure, and the reduction of FGF23/D-serine may provide a potential target for the treatment of hearing impairment complicated by chronic renal failure.

Linking Cerebrovascular Dysfunction to Age-Related Hearing Loss and Alzheimer’s Disease—Are Systemic Approaches for Diagnosis and Therapy Required?

Alzheimer’s disease (AD), the most common cause of dementia in the elderly, is a neurodegenerative disorder associated with neurovascular dysfunction, cognitive decline, and the accumulation of amyloid β peptide (Aβ) in the brain and tau-related lesions in neurons termed neurofibrillary tangles (NFTs). Aβ deposits and NFT formation are the central pathological hallmarks in AD brains, and the majority of AD cases have been shown to exhibit a complex combination of systemic comorbidities. While AD is the foremost common cause of dementia in the elderly, age-related hearing loss (ARHL) is the most predominant sensory deficit in the elderly. During aging, chronic inflammation and resulting endothelial dysfunction have been described and might be key contributors to AD; we discuss an intriguing possible link between inner ear strial microvascular pathology and blood–brain barrier pathology and present ARHL as a potentially modifiable and treatable risk factor for AD development. We present compelling evidence that ARHL might well be seen as an important risk factor in AD development: progressive hearing impairment, leading to social isolation, and its comorbidities, such as frailty, falls, and late-onset depression, link ARHL with cognitive decline and increased risk of dementia, rendering it tempting to speculate that ARHL might be a potential common molecular and pathological trigger for AD. Additionally, one could speculate that amyloid-beta might damage the blood–labyrinth barrier as it does to the blood–brain barrier, leading to ARHL pathology. Finally, there are options for the treatment of ARHL by targeted neurotrophic factor supplementation to the cochlea to improve cognitive outcomes; they can also prevent AD development and AD-related comorbidity in the future.

Epidemiology of idiopathic sudden sensorineural hearing loss in the era of big data

OBJECTIVES

Idiopathic sudden sensorineural hearing loss (ISSNHL) is a medical emergency, and delayed treatment can have permanent sequelae. However, the etiology of ISSNHL is diverse and unclear; thus, it is idiopathic. To develop an insight into this condition, patients with ISSNHL must be clearly identified. We propose an operational definition for the unambiguous identification of ISSNHL patients. Patients are identified through suggested definitions, and prevalence and general information are investigated.

METHODS

A retrospective study of patients with ISSNHL was performed using the Health Insurance and Review Assessment-National Patient Sample from 2009 to 2016. To present a new operational definition, a systematic review was conducted for studies on ISSNHL from January 2007 to June 2021. After constructing several operant definitions using the conditions that can specify patients with ISSNHL in big data, we compared each definition to propose an operational definition.

RESULTS

The important conditions required to classify patients with ISSNHL using big data were the International Classification of Diseases (ICD)-10 code, number of pure tone audiometry (PTA) tests, and whether steroids were prescribed. Among them, those who had undergone PTA tests more than twice could be clearly identified as patients with ISSNHL.

CONCLUSION

As the use of big data becomes smoother, research using national medical data is being conducted; however, the results of the studies may vary depending on how a patient with ISSNHL is classified. Clear identification of patients with ISSNHL will be beneficial for better management of this condition.

Hearing loss and brain disorders: A review of multiple pathologies

Several causative factors are associated with hearing loss (HL) and brain disorders. However, there are many unidentified disease modifiers in these conditions. Our study summarised the most common brain disorders associated with HL and highlighted mechanisms of pathologies. We searched the literature for published articles on HL and brain disorders. Alzheimer's disease/dementia, Parkinson's disease, cognitive impairment, autism spectrum disorder, ataxia, epilepsy, stroke, and hypoxic-ischaemic encephalopathy majorly co-interact with HL. The estimated incidence rate was 113 per 10,000 person-years. Genetic, epigenetic, early life/neonatal stress, hypoxia, inflammation, nitric oxide infiltration, endoplasmic reticulum stress, and excess glutamate were the distinguished modifiers identified. Various mechanisms like adhesion molecules, transport proteins, hair cell apoptosis, and neurodegeneration have been implicated in these conditions and are serving as potential targets for therapies. To improve the quality of life of patients, these understandings will improve clinical diagnoses and management of HL and brain disorders.