Age-Related Changes in the Cochlea and Vestibule: Shared Patterns and Processes

Abstract

Both age-related hearing loss (ARHL) and age-related loss in vestibular function (ARVL) are prevalent conditions with deleterious consequences on the health and quality of life. Age-related changes in the inner ear are key contributors to both conditions. The auditory and vestibular systems rely on a shared sensory organ – the inner ear – and, like other sensory organs, the inner ear is susceptible to the effects of aging. Despite involvement of the same sensory structure, ARHL and ARVL are often considered separately. Insight essential for the development of improved diagnostics and treatments for both ARHL and ARVL can be gained by careful examination of their shared and unique pathophysiology in the auditory and vestibular end organs of the inner ear. To this end, this review begins by comparing the prevalence patterns of ARHL and ARVL. Next, the normal and age-related changes in the structure and function of the auditory and vestibular end organs are compared. Then, the contributions of various molecular mechanisms, notably inflammaging, oxidative stress, and genetic factors, are evaluated as possible common culprits that interrelate pathophysiology in the cochlea and vestibular end organs as part of ARHL and ARVL. A careful comparison of these changes reveals that the patterns of pathophysiology show similarities but also differences both between the cochlea and vestibular end organs and among the vestibular end organs. Future progress will depend on the development and application of new research strategies and the integrated investigation of ARHL and ARVL using both clinical and animal models.

Chronic vestibular syndromes in the elderly: Presbyvestibulopathy—an isolated clinical entity?

“…Age-related deterioration of vestibular function and response is in line with common findings in other sensory systems, for example, in the visual, somatosensory, and auditory systems [5][6][7]. Its causes are obvious and multifactorial.…”

“…Age‐related hypofunction in the peripheral vestibular system is a well‐known finding similar to impairments in other sensory systems such as polyneuropathy and impaired visual and auditory acuity [33]. However, the clinical impact of mild vestibular hypofunction in humans is still not well understood [7]. Since the entity of PVP was defined recently in analogy to presbyopia and presbyacusis, there is still a lack of epidemiological studies describing the frequency, characteristics, and clinical impact of PVP [12].…”

“…Age-related hypofunction in the peripheral vestibular system is a well-known finding similar to impairments in other sensory systems such as polyneuropathy and impaired visual and auditory acuity [33]. However, the clinical impact of mild vestibular hypofunction in humans is still not well understood [7].…”

“…Its causes are obvious and multifactorial. First, there is a loss of sensory function with increasing age due to various peripheral structural mechanisms, for example, decrease in the number of hair cells and cells in Scarpa's ganglion as well as numbers and volumes of otoconia in the otoliths in the vestibular end organs [7,8]. Second, various age-related anatomical but also functional alterations have been reported for the central vestibular system; anatomical changes concerning the volume and neuronal density of the vestibular nuclear complex as well as of the cerebellar vermis have been detected [9][10][11].…”

Transcriptome-Guided Identification of Drugs for Repurposing to Treat Age-Related Hearing Loss

“…Moreover, previous work has documented age-related atrophy of the endocochlear potential (EP) generating substructures, including the stria vascularis (SV) and spiral ligament (SL), which contributes to hearing loss across frequencies [12]. A variety of cellular and molecular mechanisms have been implicated in age-related loss of cochlear functioning, including oxidative stress, inflammation, and apoptosis [13]. Finally, genetic factors, including syndromic and non-syndromic hearing loss mutations and common genetic variants in the population [9,14], as well as environmental factors, especially noise and ototoxins [9], contribute to ARHL.…”