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

Estimating the impact of different types hearing loss on cognitive decline and the joint effect of hearing loss and depression on cognitive decline among older adults in China

BACKGROUND

Current research lacks examination of the relationship between different subtypes of hearing loss (HL) and cognitive decline (CD). Additionally, the co-effects of HL and depression on CD remain unexplored. This study aims to investigate the relationship between HL, various types of HL, and CD, as well as the combined impact of HL and depression on CD.

METHODS

Data from a total of 5218 older adults who participated in the most recent three waves of Chinese Longitudinal Healthy Longevity Survey (CLHLS) (2011-2012, 2014, and 2018) were included. HL was assessed through self-report and objective measures. CD was defined as a decrease in MMSE score of≥3 between any two survey periods for older adults. Cox proportional hazards model was applied to analyzed.

RESULTS

Among Chinese older adults, bilateral HL (HR = 1.202, 95%CI = 1.093-1.322, P < 0.001), onset of HL after the age of 40 (HR = 1.155, 95%CI = 1.056-1.264, P = 0.002), and chronic HL (HR = 1.143, 95%CI = 1.040-1.255, P = 0.005) posed a greater risk. HL (HR = 1.146, 95%CI = 1.048-1.254, P = 0.003) and depression (HR = 1.162, 95%CI = 1.038-1.301, P = 0.009) were independently or jointly associated with CD. Participants who were simultaneously exposed to both HL and depression experienced the highest risk of CD (HR = 1.314, 95%CI = 1.117-1.545, P = 0.001).

LIMITATIONS

Given the observational design, unidentified confounding variables may still be present, such as whether to wear a hearing aid.

CONCLUSION

This study emphasizes the high risk of specific types of HL for CD and the importance of implementing health interventions that address both physiological and psychological aspects to enhance cognitive function and prevent CD in older adults.

Abnormal white and gray matter functional connectivity is associated with cognitive dysfunction in presbycusis

Presbycusis is characterized by high-frequency hearing loss and is closely associated with cognitive decline. Previous studies have observed functional reorganization of gray matter in presbycusis, but the information transmission between gray matter and white matter remains ill-defined. Using resting-state functional magnetic resonance imaging, we investigated differences in functional connectivity (GM-GM, WM-WM, and GM-WM) between 60 patients with presbycusis and 57 healthy controls. Subsequently, we examined the correlation between these connectivity differences with high-frequency hearing loss as well as cognitive impairment. Our results revealed significant alterations in functional connectivity involving the body of the corpus callosum, posterior limbs of the internal capsule, retrolenticular region of the internal capsule, and the gray matter regions in presbycusis. Notably, disrupted functional connectivity was observed between the body of the corpus callosum and ventral anterior cingulate cortex in presbycusis, which was associated with impaired attention. Additionally, enhanced functional connectivity was found in presbycusis between the internal capsule and the ventral auditory processing stream, which was related to impaired cognition in multiple domains. These two patterns of altered functional connectivity between gray matter and white matter may involve both bottom-up and top-down regulation of cognitive function. These findings provide novel insights into understanding cognitive compensation and resource redistribution mechanisms in presbycusis.

The Laterality of Age-Related Hearing Loss and Depression

OBJECTIVE

There is a known association between hearing loss (HL) and depressive symptoms. The objective was to establish if there is a stronger association with the left or right ear.

STUDY DESIGN

Cross-sectional analysis of an ongoing prospective epidemiologic cohort study.

SETTING

Hispanic Community Health Study (US, multicentered).

PATIENTS

Five thousand three hundred and twenty-eight adults 2:50 years old.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The main outcome was depressive symptoms, measured by the 10-Item Center for Epidemiologic Studies Depression Scale-10 (CESD-10) and defined continuously and binarily. Subjects with CESD-10 2: 10 were categorized as having clinically significant depressive symptoms (CSDS). Linear and logistic regressions were performed to assess the association between depressive symptoms and hearing in each ear, controlling for hearing aid use, age, sex, educational level, study site, geographic background, cardiovascular disease, and antidepressant use.

RESULTS

Mean age was 58.5 ± 6.3 years. Mean pure-tone average (PTA) was 20.3 ± 11.7 dB (range = 0 - 125) in the right ear and 20.3 ± 12.4 dB (range = -2.5 to 120) in the left. Multivariable regression adjusting for covariates demonstrated significant associations between depressive symptoms and HL in both the left and right ear. For every 20-dB worsening in right ear PTA, there was 0.89-point increase in CESD-10 (95% confidence interval = 0.59 - 1.2), and odds of CSDS increased 1.31 times (1.17 - 1.46). For every 20-dB worsening in left ear PTA, there was a 0.85-point increase in CESD-10 (0.55 - 1.14), and odds of CSDS increased 1.34 times (1.20 - 1.49).

CONCLUSIONS

Worsening hearing in the right and left ears individually was associated with increased depressive symptoms and odds of CSDS. No ear laterality was demonstrated.

The Laterality of Early Age-Related Hearing Loss and Brain β-Amyloid

OBJECTIVE

Worse hearing was linked to higher brain β-amyloid, a pathologic hallmark of Alzheimer's disease, in a recent study. We analyze the associations between β-amyloid and early age-related hearing loss in the right versus left ear to explore the laterality of this relationship.

STUDY DESIGN

Cross-sectional analysis of a prospective cohort study.

SETTING

Tertiary referral center.

PARTICIPANTS

Ninety-eight late middle-age adults.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The primary outcome was whole brain and regional β-amyloid standardized uptake value ratio (SUVR) on positron emission tomography. The exposure was hearing in the right and left ear, measured by pure tone average (PTA) and word recognition score (WRS). Linear regression analyzed the association between β-amyloid and hearing in each ear, adjusting for potential confounders, including age, gender, education, cardiovascular disease, and hearing aid use.

RESULTS

Mean age ± standard deviation was 64.3 ± 3.5 years. Mean PTA was 20.4 ± 8.8 dB. Multivariable regression adjusting for covariates demonstrated that a 10 dB worsening in PTA in the left ear was associated with significantly higher β-amyloid (SUVR) in the bilateral cingulate gyri (right coefficient: 0.029 [95% confidence interval: 0.003-0.054]; left: 0.029 [0.003-0.055]), bilateral frontal lobes (right: 0.024 [0.002-0.047]; left: 0.028 [0.006-0.049]), and the right temporal lobe (0.019 [0.002-0.037]). Consistent results were observed when WRS served as the exposure. No associations were observed between β-amyloid and PTA or WRS in the right ear.

CONCLUSIONS

Worse hearing in the left ear, but not the right ear, was associated with higher β-amyloid. This might relate to asymmetric central auditory processing.

The Laterality of Age-related Hearing Loss and Cognition

Objectives

To analyze the association between neurocognitive performance and age-related hearing loss in the right and left ear, individually.

Design

Subjects included 5277 participants (≥50 years) from the general Hispanic population who underwent audiometric testing in a US multicentered epidemiologic study. Linear regression was performed to assess the cross-sectional association between cognitive performance (Digit Symbol Substitution Test [DSST], Word Frequency Test, Spanish-English Verbal Learning Test [SEVLT] 3 Trials, SEVLT Recall, and Six-Item Screener) and hearing in each ear (4-frequency pure-tone average), adjusting for age, sex, education, cardiovascular disease, and hearing aid use.

Results

Mean age was 58.4 ± 6.2 years; 3254 (61.7%) were women. Mean pure-tone averages were 20.2 ± 11.7 dB (right ear) and 20.2 ± 12.3 dB (left ear). Multivariable regression demonstrated significant associations between all cognitive tests and hearing loss in both ears.

Conclusions

Worsening hearing loss in the right and left ear was associated with decreased performance across all tests. No laterality in the association was demonstrated.

Pure Tone Audiometry and Hearing Loss in Alzheimer's Disease: A Meta-Analysis

An association between age-related hearing loss (ARHL) and Alzheimer's Disease (AD) has been widely reported. However, the nature of this relationship remains poorly understood. Quantification of hearing loss as it relates to AD is imperative for the creation of reliable, hearing-related biomarkers for earlier diagnosis and development of ARHL treatments that may slow the progression of AD. Previous studies that have measured the association between peripheral hearing function and AD have yielded mixed results. Most of these studies have been small and underpowered to reveal an association. Therefore, in the current report, we sought to estimate the degree to which AD patients have impaired hearing by performing a meta-analysis to increase statistical power. We reviewed 248 published studies that quantified peripheral hearing function using pure-tone audiometry for subjects with AD. Six studies, with a combined total of 171 subjects with AD compared to 222 age-matched controls, met inclusion criteria. We found a statistically significant increase in hearing threshold as measured by pure tone audiometry for subjects with AD compared to controls. For a three-frequency pure tone average calculated for air conduction thresholds at 500-1,000-2,000 Hz (0.5-2 kHz PTA), an increase of 2.3 decibel hearing level (dB HL) was found in subjects with AD compared to controls (p = 0.001). Likewise, for a four-frequency pure tone average calculated at 500-1,000-2,000-4,000 (0.5-4 kHz PTA), an increase of 4.5 dB HL was measured (p = 0.002), and this increase was significantly greater than that seen for 0.5-2 kHz PTA. There was no difference in the average age of the control and AD subjects. These data confirm the presence of poorer hearing ability in AD subjects, provided a quantitative estimate of the magnitude of hearing loss, and suggest that the magnitude of the effect is greater at higher sound frequencies. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier: CRD42021288280.

Longitudinal associations of subclinical hearing loss with cognitive decline

BACKGROUND

Several studies have demonstrated that age-related hearing loss is associated with cognitive decline. We investigated whether subclinical hearing loss (SCHL), or imperfect hearing traditionally categorized as normal (pure tone average ≤25 dB), may be similarly linked to cognitive decline and risk of incident mild cognitive impairment (MCI)/dementia.

METHODS

Participants from the Baltimore Longitudinal Study of Aging were cognitively normal adults ≥50 years old with cognitive assessments from 1991-2019 and pure-tone average ≤25 dB measured between 1991-1994 (n=263). The exposure was hearing based on the better ear pure-tone average. Outcomes were test scores in various cognitive domains. Multivariable linear-mixed effects models modeled the association between hearing and change in cognition over time, adjusting for age, sex, education, vascular burden, and race. Kaplan-Meier survival curves and Cox proportional hazards models portrayed associations between hearing and incident MCI/dementia diagnosis based on predefined criteria.

RESULTS

Of 263 participants, 145 (55.1%) were female; mean age was 68.3 years (standard deviation, SD=8.9). Follow-up ranged up to 27.7 years (mean=11.7 years). Adjusting for multiple comparisons, a 10-dB increase in hearing loss was associated with an annual decline of -0.02 SDs (95% confidence interval, [CI]: -0.03, -0.01) in Letter Fluency. No significant relationships were observed between hearing and incident MCI/dementia.

CONCLUSIONS

A relationship between SCHL and cognitive decline was observed for the Letter Fluency test. Further studies are necessary to determine when in the spectrum of hearing loss there begins to be an observable relationship between hearing and cognitive decline.