Hearing loss has a profound negative impact on quality of life due to severe impairment of an individual’s cognitive and communicative abilities. The prevalence of this harmful health condition is alarming; according to the 2019 Global Burden of Disease (GBD) study, more than 1.57 billion people are affected worldwide (McDaid et al., 2021). Older adults are especially vulnerable — the incidence of reported hearing loss ranges from 30%-60% for people over 65 years to 70%-90% for the over 85 years age group (Sarant et al., 2020).
Speech and language difficulties stemming from hearing loss are traumatizing for patients’ mental health and wellbeing. Additionally, multiple studies have linked a decline in hearing ability to cognitive impairment. In particular, the Lancet Commission (2017) stated that hearing loss accounts for approximately 9.1% of the modifiable risks for dementia (as cited in Sarant et al., 2020, p.2). This paper explores the impact of hearing loss on cognition in order to explain how a decline in hearing ability leads to impairment of cognitive function.
The impact of hearing loss on cognitive impairment can be explained through the nature of the hearing. Most importantly, hearing is a complex act that involves two inter-related components of the auditory system — the peripheral and central auditory systems (Powell et al., 2021). The peripheral system consists of the outer ear, eardrum, middle ear bones, and cochlea. Their work gradually transforms sound waves, or acoustic energy, into an electrical signal sent to the brain through the auditory nerve (Musiek & Baran, 2018, as cited in Powell et al., 2021, p.2).
Therefore, the peripheral and the central auditory systems act together to receive, encode, and transmit sound to the brain. In this regard, peripheral hearing can be understood as sound detection, whereas central hearing impacts the brain’s ability to understand environmental sounds. When one of the auditory system’s components works improperly, an individual experiences hearing loss.
Various non-modifiable and modifiable risk factors can impair hearing ability. Regarding non-modifiable factors, women have a lower hearing loss prevalence than men. Additionally, Black adults are less predisposed to hearing loss than Hispanic and White adults (Powell et al., 2021). The modifiable factors include but are not limited to lifestyle and various health conditions, such as viral infections and chronic diseases (Powell et al., 2021).
However, age acts as the most frequent risk factor for hearing loss. According to Slade et al. (2020), the age-related degeneration of outer and inner cells within the cochlea hinders the transmission of the auditory signals, which results in reduced effectiveness of peripheral hearing. As a result, the auditory signals diminish; the brain cannot process the information on environmental sounds as effectively as before. In the end, the declining hearing creates the preconditions that enable four potential mechanisms for cognitive function impairment and the development of dementia.
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