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

Abstract

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.

Cognitive Screening and Hearing Assessment in Patients With Chronic Tinnitus

“…Compared to the German cohort, the MED group had lower MoCA scores and higher PTA thresholds in the bilateral SNHL, unilateral SNHL, and normal hearing subgroups. The association between higher HL and lower cognitive function is known from individuals with Alzheimer disease, who have worse hearing thresholds in PTA than age-matched controls [ 29 ]. Our findings support an association of MoCA with the education level, age, hearing threshold at 8 kHz, and THI scores and confirm previous studies reporting the association of high-frequency HL and cognitive impairment [ 30 , 31 ].…”

Clinical Practice Guideline: Age‐Related Hearing Loss

“…Although causal relationships are incompletely understood, MAs and SRs demonstrate a clear association between ARHL and cognitive loss. [196][197][198][199][200] ARHL worsens cognitive decline in those with mild cognitive impairment 201 and HL is worse in those with cognitive impairment, specifically Alzheimer's. 196 Most cognitive domains, regardless of each domain's reliance on auditory function, are impaired by hearing loss, including executive function, processing speed, working memory, language, verbal memory, and general cognition.…”

“…[196][197][198][199][200] ARHL worsens cognitive decline in those with mild cognitive impairment 201 and HL is worse in those with cognitive impairment, specifically Alzheimer's. 196 Most cognitive domains, regardless of each domain's reliance on auditory function, are impaired by hearing loss, including executive function, processing speed, working memory, language, verbal memory, and general cognition. 202 Beyond functional decline, ARHL is also associated with brain atrophy, in addition to expected atrophy in the auditory cortex.…”

“…Cognitive function and HL have been extensively investigated. Although causal relationships are incompletely understood, MAs and SRs demonstrate a clear association between ARHL and cognitive loss 196‐200 . ARHL worsens cognitive decline in those with mild cognitive impairment 201 and HL is worse in those with cognitive impairment, specifically Alzheimer's 196 .…”

Returning Individual Research Results to Vulnerable Individuals

“…In some instances, such as with the elderly with hearing loss and those with amyotrophic lateral sclerosis, the likelihood of cognitive vulnerability may be increased. 40,41 Moreover, individuals with communicative vulnerability are at increased risk of economic vulnerability (https://www.afb.org/research-and-initiatives/employment/ reviewing-disability-employment-research-people-blind-vis ually, last accessed March 14, 2022). Furthermore, stigmatization and other group harms may be particularly relevant to those with communicative vulnerability.…”