Clinicians working with older people have long been aware that cognitive and hearing impairments often co-occur. There has been an increase in research examining hearing loss and dementia over the last decade, stimulated by the first Lancet Commission report on dementia prevention, intervention and care (Livingston et al., 2017), which identified hearing loss from midlife onwards as the largest potentially modifiable population-attributable risk factor for dementia. From this, further research has explored the accuracy of this estimate, the possible underlying mechanisms linking hearing conditions and dementia, and the potential for hearing interventions to reduce the risk of future dementia or to modify the trajectory of cognitive decline for those at risk.

Dementia is a group of symptoms caused by different diseases that affect the brain, impacting 55 million people worldwide (World Health Organization, 2023). There is no known cure, but evidence suggests lifestyle modification can help reduce dementia risk or slow its progression (Livingston et al., 2024; Patterson, 2018; World Health Organisation, 2025). Hearing loss is defined as a reduced ability to detect sounds compared to someone with normal hearing, typically characterised by pure-tone audiometric hearing thresholds of 20dB hearing level (HL) or worse in each ear (World Health Organization, 2024). The primary management strategy for hearing loss is the provision of hearing aids or cochlear implants to provide access to sounds. It affects over 1.5 billion people globally and is a significant contributor to years lived with disability (World Health Organization, 2024; Haile et al., 2024). The greatest burden is in low- and middle-income countries, where access to hearing care remains limited (Newall, 2025). Hearing loss and dementia, both individually and in combination, reduce independence, increase social isolation, impair communication, and increase the burden of care compared to people living without the conditions (Shukla, 2020; Azevedo, 2021).

Hearing loss often goes undetected and unmanaged. In the context of an ageing population, the potential societal impact of addressing hearing loss as a potentially modifiable risk factor for dementia is substantial (Stancel-Lewis et al., 2025). Hearing health is an important consideration for public health, with implications extending beyond individual communication outcomes to healthcare systems, social care demand, and health inequalities (Stancel-Lewis et al., 2025; Parmar et al., 2025). The intersection of sensory and cognitive decline presents a growing challenge for healthcare systems. This review contributes to the broader field of ageing research by summarising the evidence linking dementia and hearing loss and providing an overview of key issues. We do so by asking: (1) how much dementia risk is attributable to hearing loss? (2) if hearing loss and dementia are linked, what mechanisms could explain this connection? and (3) can hearing interventions modify dementia risk and/or the trajectory of cognitive decline? We then explore areas of current and future research as they relate to the care and management of people with coexisting dementia and hearing loss.

Several hypotheses have been proposed to account for the observed relationship between hearing loss in midlife and the increased incidence of dementia (see Figure 1).

The plausibility and relevance of the proposed mechanisms may depend in part on the timing of hearing loss across the life course. Much of the evidence has focused on hearing loss in mid-life as a risk factor for dementia. Hearing loss in mid-life may have long-term effects on cognitive reserve, brain structure and social engagement which may increase vulnerability to neurodegeneration later in life (Livingston et al., 2017; Livingston et al., 2020; Livingston et al., 2024; Lin et al., 2011). In contrast, hearing loss occurring in later life may in some cases be a consequence of prodromal dementia-related pathology (Hardy et al., 2016; Griffiths et al., 2020). Distinguishing between these pathways is essential when interpreting mechanistic evidence and evaluating the potential impact of hearing interventions.

Proposed causal mechanisms variously suggest that: (i) hearing loss directly elevates dementia risk; (ii) hearing loss causes knock-on changes that indirectly elevate the risk; or (iii) a combination of the two. Additionally, dementia may cause an elevated risk of hearing loss diagnosis as the early brain changes related to dementia could contribute to hearing loss which is referred to as a “reverse causal” mechanism. This area is evolving, and within the literature, some interpretations of the proposed mechanisms overlap or are used interchangeably.

Although hearing interventions could benefit population health if they reduced or altered the trajectory of cognitive decline and dementia, this has yet to be robustly demonstrated. Table 1 summarises the literature on hearing interventions related to dementia and/or cognitive decline, organised by 1. controlled trials and 2. cohort and observational studies. All trials investigated hearing aids (HAs); however, marked methodological differences including recruitment, randomisation and the nature of the conditions, make the synthesis of results inappropriate.

The six trials were small (N = 102 or less), with one exception (Lin, 2023) (N = 977), and in some cases, these may be underpowered to detect intervention effects. The results of three trials were negative, reporting no difference due to HAs, with the other three equivocal.

The 23 observational and cohort studies showed large methodological differences, studies of both HAs and Cochlear Implants (CIs), with variable sample sizes (N = 14 to >500,000) and follow-up (0.5–25 years), different sampling methods and outcome measures (e.g., risk of developing dementia, performance on various cognitive measures). Eleven studies reported positive findings, for example, that HA users had lower dementia risk than non-users (Cantuaria, 2024). One reported negative findings (no differences at all; Dawes et al., 2015); and the results of the other 11 studies were unclear (including all three CI studies).

There are several systematic reviews relevant to this topic. As studies in earlier reviews were incorporated into more recent reviews, only the four most recent reviews are considered here. Two reviews (Carasek et al., 2022; Yeo et al., 2023) examined the role of cochlear implants (CIs)/HAs in modifying cognitive decline and reached positive conclusions; these included mainly observational rather than trial data, with the limitations mentioned above. A systematic review and meta-analysis reported no statistically significant benefit of HAs on cognition (Thosar et al., 2025). Yang et al. (2022) reported no definitive conclusion regarding whether HAs improve cognitive function in individuals without dementia. Machado et al. (2024) reported improvement in quality of life, but not in cognition in individuals provided with HAs.

Given the limited number of randomised controlled trials in this area, there is scope for further high-quality research. However, it is challenging to achieve double-blinding in such trials, and a suitable control group needs careful consideration. It requires a sizeable group of people with hearing loss, who are willing to be potentially randomised into a control group without a hearing intervention and remain as participants over an adequate period of follow-up. As this potentially denies them access to a management option beneficial to their hearing, it poses an ethical dilemma. Future trials could consider innovative study designs; for example, a stepped-wedge design could help mitigate ethical concerns by ensuring that all participants eventually receive the hearing intervention.

Alongside its role as a risk factor, hearing loss commonly co-occurs with dementia. While the potential for cognitive benefit remains uncertain, the value of hearing interventions lies in improving quality of life, enhancing social engagement, and supporting healthy ageing (Tang et al., 2025). HAs remain the standard management option for hearing loss (National Institute for Health and Care Excellence, 2018a), including for people already living with dementia (Ray et al., 2019). The benefits of addressing hearing loss for people living with dementia could include improvements in communication, behavioural and neuropsychiatric dementia symptoms (Mamo et al., 2017; Mamo, 2018; Dawes et al., 2019), and quality of life (Machado et al., 2024). However, people with dementia are less likely to use HAs consistently over time compared to those with intact cognition (Naylor et al., 2022). Inconsistent or discontinued HA use may contribute to an increased rate of cognitive decline, which in turn reduces capacity to maintain HA use, creating a cycle in which untreated hearing loss and cognitive impairment reinforce one another (Naylor et al., 2022).

Effective hearing interventions are not simply a matter of providing a device. Early identification of hearing loss and intervention are critical, as is offering additional support tailored to people with cognitive impairment (Calvert et al., 2025). Recent research has advocated for stronger coordination and integration between audiology and broader healthcare services, to ensure they address the complex needs of people with hearing loss and dementia (Calvert et al., 2025), especially those relying on others to manage their health. For example, in care homes, most people live with either dementia or hearing loss, and many with both, yet HA use is low (RNID, 2018; Prince, 2014; Yamada et al., 2014; Cohen-Mansfield and Taylor, 2004). Reasons for low HA use in care home settings include limited staff awareness of hearing challenges and hearing loss management options, and difficulty in discriminating symptoms and environmental and social factors (Rocks and Ferguson, 2013; Slaughter et al., 2014; Pryce and Gooberman-Hill, 2012). Research suggests that care staff need appropriate training on maintaining HAs and using communication tactics (Crosbie, 2019; Broome and Green, 2026). Despite the known barriers, there are a lack of practical solutions, thus hearing loss remains largely undetected and unmanaged in this population.

To address the lack of specific clinical guidance, interdisciplinary practice recommendations (Littlejohn et al., 2022) and best practice recommendations for the assessment and rehabilitation of hearing loss for people living with dementia (Dawes, 2022) have been published. However, there are currently no known national or international standardised approaches to the assessment and management of hearing loss in this growing population. A qualitative study of UK National Health Service (NHS) audiologists identified recommendations for clinical practice including raising awareness of the importance of hearing care, providing dementia-specific training and practice guidance for audiologists and strengthening post-audiology pathway support, for example mobile clinics within the community (Calvert et al., 2025).

While current dementia pharmacological therapies primarily aim to slow disease progression (National Institute for Health and Care Excellence, 2018b), many non-pharmacological interventions are designed to improve quality of life for people living with dementia (Livingston et al., 2024). Quality of life interventions such as music or reminiscence therapy should ensure that any hearing loss is managed to maximise accessibility and effectiveness. In this context, addressing hearing loss should be viewed as part of broader health management, with benefits for communication, social engagement, quality of life, and the management of dementia-related symptoms.

Given the large number of individuals living with one, or both conditions, it is essential that research and healthcare efforts focus not only on risk factors and mechanisms but also on improving practical care and support for this population. A recently completed James Lind Alliance (JLA) Priority Setting Partnership (PSP) in co-existing dementia and hearing conditions identified and prioritised questions for future research in this area (Heffernan et al., 2025). JLAs bring together people with lived experience and relevant professionals in partnership to identify unanswered research questions that are most important to them, shaping the future research agenda.

The priority questions arising from the PSP spanned diverse topics, from identifying and understanding causal mechanisms through to diagnosis and treatment. However, people living with hearing loss and/or dementia and their care partners have been identified as groups who encounter barriers to accessing clinical services and participating in research (NIHR, 2022; Witham et al., 2020). Barriers to research participation are compounded when people with hearing loss and dementia are also members of additional under-represented communities, such as ethnic minority groups, socio-economically disadvantaged groups, people living in care settings and the Deaf community (NIHR, 2022; Witham et al., 2020; Flower et al., 2025).

Greater efforts are needed to ensure that future research in this field is inclusive of under-represented communities. Different populations may have greater risk of one or both conditions and thus require different interventions and enhanced access to health and care services. Studies included in the Lancet Commission are predominantly from high-income countries with limited representation from groups with lower levels of education, and minority ethnic groups (Livingston et al., 2024). The latest Commission report acknowledges that population attributable risk factors are highly swayed by population factors (Livingston et al., 2024). A greater focus on inclusion in future research would help ensure that findings have real-world applications, thereby enhancing the quality of care for these populations and helping reduce health inequalities. Future research should therefore focus on identifying the optimal timing of hearing intervention across the life course, determining which subgroups are most likely to benefit, and clarifying how hearing care can be most effectively integrated into existing dementia care pathways without overburdening patients or services (Figure 2).

Improving public awareness of the benefits of addressing unmanaged hearing loss is one potential component of a public health policy aimed at increasing hearing loss management for all. Integrating hearing loss education for health professionals across the care pathway is essential to ensure that they recognise the early signs of hearing loss and provide appropriate referrals or support at the earliest opportunity. An approach recommended by the World Health Organization is to offer regular hearing screenings for adults to improve early detection of hearing loss to mitigate the long-term costs for patients and health systems more generally (World Health Organization, 2021), whereas UK opinion (Stancel-Lewis et al., 2025) suggests that targeted, risk-stratified hearing screening offers a practical and equitable approach that is consistent with the NHS 10-year health plan for England (Department of Health and Social Care, 2025).

This review highlights the complexity of the association between hearing loss and dementia, while underscoring the uncertainties that remain in determining cause, mechanisms, and the effectiveness of hearing interventions for cognitive decline and dementia risk. Translating primarily epidemiological associations into mechanistic understanding and effective clinical or public health action remains challenging.

The inclusion of hearing loss as a key potentially modifiable mid-life risk factor in successive Lancet Commission reports has been instrumental in raising awareness of the importance of hearing health for dementia risk (Livingston et al., 2017; Stancel-Lewis et al., 2025; Parmar et al., 2025). However, population-attributable fraction (PAF) estimates are model-dependent, context-specific, and rely on assumptions that are not yet fully supported by experimental evidence (Mansournia and Altman, 2018; Ishak et al., 2025). A risk for the field is that an oversimplified interpretation of these estimates may lead to the conclusion that managing hearing loss can completely remove the risk posed by it, eliminating a proportion of dementia cases. Responsible communication is therefore essential to ensure messaging is framed in the context of the available evidence to minimise any negative impacts on unrealistic expectations, help-seeking, and stigma for hearing loss and dementia (British Society of Audiology, 2024; Blustein et al., 2023; Dawes and Munro, 2024).

Evidence shows that the association between dementia and hearing loss is biologically plausible; supported by multiple hypothesised mechanisms. However these may not operate in isolation. Multiple, potentially interactive mechanisms likely link hearing loss with dementia. These include sensory deprivation, increased cognitive load, vascular and neurodegenerative processes, with shared genetic and biological risk factors; all of which are likely to contribute, rather than underly a single unifying pathway. Importantly, the relative contribution of these mechanisms may vary across individuals and across the life course, influenced by factors such as age, sex, cardiovascular health, and timing of the intervention. In particular, mechanisms associated with midlife hearing loss are more consistent with long-term causal pathways, whereas associations observed in later life may increasingly reflect prodromal neurodegenerative processes or shared ageing-related pathology. The recently proposed ‘cause–catalyst–consequence’ framework provides a valuable integrative model for conceptualising these interacting pathways and may help guide future hypothesis-driven research (Homans et al., 2017).

Despite a wealth of associative evidence, we lack substantive experimental evidence for hearing interventions to prevent or meaningfully slow cognitive decline in the general population. Importantly, studies have begun to identify meaningful targeting of hearing intervention and support (Yu et al., 2025). In the meantime, hearing interventions hearing interventions remain clinically valuable for improving communication, social participation, and overall wellbeing. These outcomes are intrinsically important to people living with dementia and their families (Yang et al., 2022; Machado et al., 2024; Tang et al., 2025; National Institute for Health and Care Excellence, 2018a; Ray et al., 2019; Mamo et al., 2017; Mamo, 2018). The ethical and practical challenges of conducting long-term trials in this area suggest that innovative study designs will be required to advance the evidence base.

The comorbidity of hearing loss and dementia is high. While dementia drug therapies primarily aim to slow disease progression, many non-pharmacological interventions focus on improving quality of life, wellbeing and social engagement (Livingston et al., 2024). Failure to identify and manage hearing loss may therefore limit the accessibility and effectiveness of these approaches. In this context, addressing hearing loss should be viewed as an integral component of holistic dementia care, with benefits for communication, participation, behavioural symptoms, and quality of life, even in the absence of disease-modifying effects.

A recurring limitation across the literature is the under-representation of diverse populations, including people from low- and middle-income countries, minority ethnic groups, socioeconomically disadvantaged communities, care home residents, and Deaf communities (Livingston et al., 2024; National Institute for Health and Care Excellence, 2018b; Heffernan et al., 2025). Given the high global prevalence of both hearing loss and dementia, and the substantial variation in access to hearing care, improving inclusivity is essential for ensuring that research findings translate into equitable public health and clinical practice.

The James Lind Alliance Priority Setting Partnership in coexisting dementia and hearing conditions highlights the importance of research questions that matter to people with lived experience, spanning mechanisms, diagnosis, intervention, and service delivery (Dawes, 2022).

Hearing loss is consistently associated with increased risk of cognitive decline and dementia, although the mechanisms underlying this relationship remain incompletely understood. Current evidence suggests that multiple biological and cognitive pathways likely interact across the life course. Clarifying these pathways and identifying individuals most likely to benefit from intervention will be essential to inform future prevention and management strategies. Progress in this field will depend on interdisciplinary collaboration, inclusive research practices, and a balanced narrative that recognises both the promise and limitations of the evidence to support the role of hearing loss management in dementia prevention and care.