Hearing and Sight in Dementia: Common, Often Missed, Mostly Treatable

Where it has been measured, most older people living with dementia also have hearing loss, and many have sight problems that could be corrected, yet many do not get the help that exists. In the United States in 2021, an estimated 79.4% of people with dementia aged 71 and over had hearing loss, and only 21.7% of them reported using hearing aids^[1]. In 2024 the Lancet Commission on dementia added vision loss to hearing loss on its list of potentially modifiable risk factors^[2].

Hearing and sight shape daily life with dementia: following a conversation, recognising a face, finding the way at night, or telling a nurse that something hurts. When a hearing aid sits broken in a drawer, or glasses are lost in a care home laundry, a person can seem more confused or withdrawn than their dementia alone would make them. This study looks at two questions: whether hearing and sight loss raise dementia risk, and whether people already living with dementia have their hearing and sight checked and supported. On the second, the answer from several countries is that too often they do not.

Hearing and sight loss are common, often untreated, and linked with dementia

Both conditions are widespread in later life. The World Health Organization estimates that over 5% of the world's population, about 430 million people, need rehabilitation for disabling hearing loss, and that among people older than 60 over 25% are affected by it; nearly 80% of people with disabling hearing loss live in low- and middle-income countries^[4]. For sight, WHO estimates that at least 2.2 billion people have a near or distance vision impairment, and that in at least 1 billion of these cases it could have been prevented or has yet to be addressed. Cataract (94 million people) and uncorrected refractive error (88.4 million) are the leading causes in that group, both treatable^[5].

The 2024 Lancet Commission meta-analysed high-quality cohort studies (666,370 people) that measured hearing objectively before anyone had dementia. People with hearing loss had a higher risk of later dementia than people with normal hearing (hazard ratio 1.37, 95% CI 1.00 to 1.87), although the studies varied a great deal (I² = 80%). Studies that tested dose-response found risk rose with every 10 dB of worse hearing, by between 4% and 24% depending on the study^[2].

For sight, the Commission cited a meta-analysis of 14 prospective cohorts covering 6,204,827 older adults who were cognitively intact at the start, of whom 171,888 developed dementia. Vision impairment was associated with a pooled relative risk of dementia of 1.47 (1.36 to 1.60). A second meta-analysis that looked at specific eye conditions found higher risk with cataract and diabetic retinopathy, but not with glaucoma or age-related macular degeneration^[2]. On that basis the Commission added vision impairment, with high LDL cholesterol, to the 12 risk factors from its 2020 report, and estimated a combined population attributable fraction of 45.3% for all 14^[2]. That figure is a modelled estimate of how much dementia might in theory be prevented or delayed if every risk were removed; the Commission itself notes that some associations "may be only partly causal". It is not a statement that hearing or sight loss caused any one person's dementia.

Studies with measured hearing and sight in whole national samples show the same pattern. In the US National Health and Aging Trends Study of 2021, which tested vision with participants' usual glasses, 12.3% of adults aged 71 and over had dementia, rising to 32.9% among those with moderate or severe distance vision impairment or blindness (an adjusted prevalence ratio of 1.72, 95% CI 1.26 to 2.35)^[6]. Using the 2022 round of the same survey, researchers estimated that 66% of people aged 65 and over had at least one hearing or vision risk factor, and put the population attributable fraction of dementia from these sensory factors at 57%, with a very wide confidence interval (8% to 61%)^[7]. As snapshots, they cannot show which came first.

Hearing aids: consistent associations, one major trial, and a mixed answer

Observational studies suggest treating hearing loss might lower risk. In UK Biobank, which recruited 437,704 adults aged 40 to 69 in England, Scotland and Wales between 2006 and 2010 and followed them through hospital and death records, people with hearing loss who did not use hearing aids had a higher risk of all-cause dementia than people without hearing loss (hazard ratio 1.42, 95% CI 1.29 to 1.56). People with hearing loss who did use aids showed no clear increase (1.04, 0.98 to 1.10)^[8]. Hearing aid use was self-reported.

A 2023 meta-analysis of 8 cohort studies with 126,903 participants, followed for 2 to 25 years, found hearing aid users had lower hazards of long-term cognitive decline than people with uncorrected hearing loss (hazard ratio 0.81, 95% CI 0.76 to 0.87), which the authors described as a 19% decrease^[9]. The Lancet Commission reported a 17% lower risk of dementia itself from the 4 studies in that review that measured it^[2].

The caution is that people who get and wear hearing aids may differ from people who do not in ways that also affect dementia risk, such as income, education, general health and access to care. Statistical adjustment can reduce but not remove that kind of difference, so these studies show association, not proof of effect.

The ACHIEVE trial tested cause and effect directly. It randomly assigned 977 adults aged 70 to 84 with untreated hearing loss and no substantial cognitive impairment, at four US sites, either to audiological counselling with hearing aids or to health education. After three years there was no overall difference in cognitive decline (difference 0.002 standard deviations, 95% CI −0.077 to 0.081)^[10]. A prespecified sensitivity analysis found the effect differed between the two groups recruited: among participants drawn from a long-running heart study, who were older and had more risk factors, the hearing intervention appeared to slow decline (difference 0.19, 0.02 to 0.36), while among healthy volunteers it did not^[2]. That is a subgroup finding, and most participants (88%) were White^[10]. ACHIEVE measured cognitive change, not dementia diagnoses, so it does not settle whether hearing aids prevent dementia.

The evidence on sight treatment is thinner still. The Lancet Commission cites a US study that followed 3,038 adults over 65 with cataracts and normal cognition: those who had cataract surgery had a lower risk of dementia than those who did not (hazard ratio 0.71, 0.62 to 0.83). A UK Biobank analysis found people with cataracts had higher dementia risk, but no difference in risk between those who had cataract surgery and healthy controls^[2]. Neither is a trial. The Commission's case for action rests partly on a simpler point: treatment for visual impairment is, in its words, "effective and cost-effective for an estimated 90% of people"^[2]. For the wider picture on modifiable risk, see our study of the Lancet Commission's risk factors.

Among people already living with dementia, sensory loss is common and often missed

For people who already have a diagnosis, the question is quality of life, communication and safety. The US national survey that tested hearing in 2,613 Medicare beneficiaries aged 71 and over estimated that 79.4% of those with dementia had hearing loss, rising from 61.1% at ages 71 to 74 to 94.2% at 85 and over. Only 21.7% of those with hearing loss reported using hearing aids^[1].

England's PrOVIDe study examined the eyes of 708 people with dementia aged 60 to 89, 389 living in the community and 319 in care homes, through home sight tests at 20 NHS sites. Wearing their current glasses, 32.5% had sight worse than 6/12, a common threshold for visual impairment (16.3% on the stricter 6/18 threshold). Of those with impairment, 44% could have been corrected with new glasses; almost half of the remaining impairment was associated with cataract and was therefore potentially remediable^[3]. Visual impairment (measured with current glasses) was more common among care home residents (odds ratio 2.19, 95% CI 1.30 to 3.73, adjusted for age, sex and cognitive score). Visual acuity could not be measured in 34.2% of care home residents compared with 2.6% of those living at home, but the main parts of the eye examination could be done in more than 80% of participants^[3]. Family carers and care workers underestimated what an eye examination could achieve, and people with dementia and their carers did not know home sight tests were available^[3].

A 2023 scoping review of 36 studies found that reported prevalence of visual impairment or specific eye disease among older people with dementia ranged from 0.2% to 74%, because studies used different settings, tests and definitions. Documented impacts included more hospital use, greater dependency and reduced social engagement^[11]. The overlap is large in care homes. In Switzerland, assessments of 132,880 people aged 65 and over newly admitted to 715 nursing homes between 2010 and 2019 recorded a sensory impairment in 57.3% of residents, and cognitive impairment in 57.3%. Cognitive impairment was most strongly associated with combined hearing and vision impairment (prevalence ratio 1.58, 95% CI 1.56 to 1.60), then hearing impairment (1.35) and vision impairment (1.18)^[12].

Many memory tests depend on hearing instructions or reading words and pictures. NICE's dementia guideline for England (NG97) asks clinicians to investigate sensory impairment such as sight or hearing loss as a possible reversible cause of cognitive decline before referring for a dementia diagnosis, and to take account of sensory disabilities that could affect the results of assessment scales^[13]. Undetected hearing or sight loss can make cognition look worse than it is. For how diagnosis is measured and missed, see our study of dementia diagnosis rates.

Broken, lost and unfitted: where sensory care falls short

Guidelines in some countries already expect sensory care to be part of dementia care. In England, NICE asks that people living with dementia be encouraged to have an eye test soon after diagnosis if they have not had one recently, and then every 2 years, and that people who cannot organise appointments themselves be considered for referral^[13]. NICE's hearing loss guideline (NG98) asks clinicians to consider referring adults with diagnosed or suspected dementia or mild cognitive impairment to audiology, and to consider a hearing assessment every 2 years for those not already diagnosed with hearing loss^[14]. We found no national data on how often these are met.

What the evidence does show is the gap in practice. A national survey of 887 staff in 117 care homes across England found high awareness of sensory problems among residents with dementia, but infrequent training; most front-line staff felt they lacked the skills to support residents' use of hearing aids and glasses. The most commonly reported reasons devices went unused were broken and lost aids and glasses, and residents not tolerating them. The authors concluded that "training and practice of sensory health care" for residents with dementia in long-term care in England "is lacking"^[15].

Help can be designed to fit. The European SENSE-Cog trial randomised 252 people with dementia and hearing and/or vision loss, each with a study partner, to an 18-week home-based sensory support programme or usual care. Of 124 people in the support arm assessed for hearing loss, 101 (81%) were prescribed hearing aids and 43 (35%) glasses, and care partners were central to helping people use them^[16]. We could not verify the trial's main quality-of-life results at source, so we do not report them. For care homes more broadly, see our studies of dementia in care homes and the wider Dementia & Health research library.

What the evidence asks of us

The research on whether treating hearing and sight loss prevents dementia is not settled, and it should be described honestly: consistent associations, one large trial with no overall effect on cognitive decline and a possible benefit in people at higher risk, and almost no trial evidence for sight. But the case for good sensory care for people living with dementia does not depend on that question. Hearing and seeing well matter for communication, dignity and safety, whatever their effect on risk.

• Make hearing and eye care accessible and affordable. The Lancet Commission recommends that hearing aids be "accessible for people with hearing loss"^[2]. WHO estimates that an additional annual investment of less than US$1.40 per person would scale up ear and hearing care globally, with a return of nearly US$16 for every dollar over ten years^[4], and puts the cost gap for addressing unmet need in vision at about US$25 billion^[5]. The need is largest in low- and middle-income countries.
• Check hearing and sight as part of dementia assessment and after diagnosis, as NICE recommends, and record the results so that later services know what support a person uses^[13][14].
• Bring tests to people. Home and care-home sight tests were feasible for most people with dementia in PrOVIDe, yet many families did not know they existed^[3].
• Train and equip care staff to clean, maintain, charge, label and find hearing aids and glasses, and to communicate well with residents who have sensory loss^[15].
• Fund better research: trials that include people already living with dementia, more diverse participants than ACHIEVE's mostly White sample^[10], outcomes that matter to people with dementia and carers, and consistent ways of measuring sight and hearing so countries can be compared^[11].

Language: this piece uses person-first language ("people living with dementia", "people with dementia"), as most dementia organisations and people with lived experience prefer, and uses clinical terms such as "Alzheimer's disease" or "mild cognitive impairment" only where a study, dataset or diagnosis refers to that specific condition.

Why we're publishing this

Public debate about hearing, sight and dementia tends to focus on prevention headlines, while the everyday problem is hearing aids and glasses that go missing and sight and hearing that go unchecked. We have gathered the best evidence we could verify, from several countries, so that dementia organisations can make the case for sensory care with figures they can cite, and with an honest account of what the prevention research does and does not show.

How to read this data

Most figures here come from observational studies: cohorts that follow people over time (UK Biobank, the studies pooled by the Lancet Commission) and cross-sectional surveys that measure everything at once (the US National Health and Aging Trends Study, the Swiss nursing home assessments, PrOVIDe in England). These show association, not cause. Hazard ratios, prevalence ratios and odds ratios measure different things and are not interchangeable. Population attributable fractions are modelled estimates of potential prevention under assumptions about causation, and different models give different answers (45.3% for all 14 Lancet risk factors worldwide; 57% for sensory factors in one US analysis). ACHIEVE is the only randomised trial whose outcome we report, and it measured cognitive decline, not dementia. Hearing, sight and dementia were measured differently across studies, so figures from different countries should not be compared directly. The US, England and Switzerland feature because they have measured data; we found far less evidence from low- and middle-income countries, where WHO estimates most unmet need lies.

Use this data

Free to cite with attribution to Understanding Aging. Charities, carers' groups, campaigners and journalists are welcome to reuse these figures and charts. For the underlying figures as a spreadsheet, get in touch.

Important: This article summarises published research and statistics for general information. It is not medical, care or financial advice and cannot be used to diagnose, treat or predict anything about an individual. If you have concerns about your own or someone else's memory or health, please speak to a GP or another qualified health professional.

Sources

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