The Effects of Age-Related Hearing Loss on the Brain and Cognitive Function

Abstract

Age-related hearing loss (ARHL) is a common problem for older adults, leading to communication difficulties, isolation, and cognitive decline. Recently, hearing loss has been identified as potentially the most modifiable risk factor for dementia. Listening in challenging situations, or when the auditory system is damaged, strains cortical resources, and this may change how the brain responds to cognitively demanding situations more generally. We review the effects of ARHL on brain areas involved in speech perception, from the auditory cortex, through attentional networks, to the motor system. We explore current perspectives on the possible causal relationship between hearing loss, neural reorganisation, and cognitive impairment. Through this synthesis we aim to inspire innovative research and novel interventions for alleviating hearing loss and cognitive decline.The Ageing Ear: Tired of Listening? ARHL, or presbycusis, is characterised by gradually developing high-frequency hearing loss, often accompanied by poor speech discrimination, and may begin to surface in the fourth decade of life [1]. The prevalence of ARHL increases with age, affecting N40% of people over 50 years old, rising to~71% of people over 70 years [2]. For most people this is a relatively unremarkable part of the ageing process (Box 1), but some individuals with ARHL experience effort and difficulties in understanding speech, hindering communication and socialisation [3]. Increased listening effort may lead older adults to avoid social interaction, exacerbating loneliness and depression, and reducing well-being [4]. Recent research further shows that hearing loss is associated with cognitive decline and dementia [5,6]. However, although there is reasonable evidence for hearing loss as a marker for risk of cognitive decline, it is not yet clear whether there is a causal effect of hearing loss on cognitive decline. Collating the most recent evidence on how ARHL affects the brain provides valuable information on the possible underlying mechanisms and causal relationships between hearing loss, neural changes, and dementia. This review discusses the physiology of ARHL, from the peripheral auditory system to the auditory cortex, and to global neural changes that accompany ARHL. We focus on the impact of these cortical changes on cognitive functioning during ageing, and explore the evidence for a possible causal relationship between ARHL-related changes in neural functioning and cognitive decline.The Peripheral and Subcortical Auditory Systems in Age-Related Hearing Loss ARHL is attributed to sensory, metabolic, or neural changes in the peripheral auditory system which affect hearing ability. Sensory ARHL is characterised by degeneration of outer and inner hair cells within the cochlea, of which the inner cells are responsible for the transduction of auditory signals. Atrophy originates in the basal end of the cochlea, and over time progresses to the apex. Basal atrophy manifests in the high-frequency hearing loss typical of sensory ARHL [7]. It has b...

Conceptual Model of Hearing Health Inequalities (HHI Model): A Critical Interpretive Synthesis

“…Nevertheless, it should be noted that the magnitude of the effect of age on hearing loss varies considerably among individuals. Nearly one in three people older than 70 years old do not develop high-frequency hearing loss, a condition that has traditionally been linked with aging ( Slade et al., 2020 ). Despite diligent research over the past decades, our understanding of age-related hearing loss is very limited (Bowl & Dawson, 2019, p. 1).…”

Cortical tracking of unheard formant modulations derived from silently presented lip movements and its decline with age

“…This points to a possible top-down influence of stored syntactic information provided by delta-band tracking, which also seems to be deteriorating with increasing age both in occipital and cingulate cortex. Interestingly, age-related hearing loss also leads to a volume reduction in anterior cingulate cortex (Slade et al, 2020), which in turn also leads to more memory impairments and cognitive deficits (Belkhiria et al, 2019). These and our current results strengthen the notion that the cingulate cortex has an important function also in visual speech processing, as this also goes in line with the mentioned compensatory mechanism in anterior cingulate cortex (ACC) (Erb & Obleser, 2013).…”

Translational and interdisciplinary insights into presbyacusis: A multidimensional disease

“…Evidence for these widespread effects in humans includes associations between hearing thresholds and brain morphology. A close examination of these findings and their putative mechanisms is important because some suggest that these findings can explain age-related changes in speech recognition, as well as associations between elevated pure-tone thresholds and lower general cognitive function ( Slade, et al., 2020 for review). Here we explain why caution is warranted when considering brain structure correlations as evidence for a hypothesized relationship between hearing loss and general cognitive function.…”