Hearing Loss and Cognition: What We Know and Where We Need to Go

Abstract

Although a causal association remains to be determined, epidemiologic evidence suggests an association between hearing loss and increased risk of dementia. If we determine the association is causal, opportunity for targeted intervention for hearing loss may play a fundamental role in dementia prevention. In this discussion, we summarize current research on the association between hearing loss and dementia and review potential casual mechanisms behind the association (e.g., sensory-deprivation hypothesis, information-degradation hypothesis, common cause). We emphasize key areas of research which might best inform our investigation of this potential casual association. These selected research priorities include examination of the causal mechanism, measurement of co-existing hearing loss and cognitive impairment and determination of any bias in testing, potential for managing hearing loss for prevention of dementia and cognitive decline, or the potential to reduce dementia-related symptoms through the management of hearing loss. Addressing these research gaps and how results are then translated for clinical use may prove paramount for dementia prevention, management, and overall health of older adults.

The association of hearing loss with depressive symptoms and cognitive function among older people: Results from the Brazilian Longitudinal Study of Aging

“…Indeed, many prospective cohort studies have shown a positive effect of hearing aid use on cognitive function and dementia risk reduction. [47][48][49] These results may indicate that individuals with poorer cognition might be having hearing aids prescribed to them more often, but probably at a time when their cognition is so deteriorated that the aid does not exert any meaningful protective effect.…”

“…Furthermore, we found an unexpected association between an effective use of a hearing aid with poorer cognition, which may be explained by reverse causality bias resulting from our cross‐sectional design. Indeed, many prospective cohort studies have shown a positive effect of hearing aid use on cognitive function and dementia risk reduction 47–49 . These results may indicate that individuals with poorer cognition might be having hearing aids prescribed to them more often, but probably at a time when their cognition is so deteriorated that the aid does not exert any meaningful protective effect.…”

Distinct disease mechanisms may underlie cognitive decline related to hearing loss in different age groups

“…Those results support the idea that perhaps sensory deprivation mechanisms may play a role in the association of hearing loss and cognitive decline in the oldest-to-old. In addition to hearing loss, other factors that are associated with hearing loss such as social isolation, depression and frailty may contribute to sensory deprivation in this group,38 and future research should aim to study the influence of such additional factors.…”

Cognitive Performance, Sociodemographic Factors, Pure-Tone Audiometry, and their Association with Speech Discrimination: A Prospective Population-Based Study of 1,061 Older Adults

“…Although numerous studies have suggested a link between hearing loss-assessed both by pure tones and recently by speech discrimination-and patients' cognitive status (2,8,21,22), limited research has investigated the potential reverse relationship, where cognitive performance might itself influence audiometric testing results. Traditionally, speech discrimination is thought to require greater central processing than pure-tone audiometry and is more representative of functional hearing ability (22). Yet, the current study suggests instead that WRSs are largely driven by pure-tone thresholds requiring limited central processing, which results in minimal explanatory influence attributable to cognitive performance status.…”