Hearing and vision loss

Hearing loss becomes more common with each decade of age. The World Health Organization estimates that more than 5% of the world's population, or 430 million people, have disabling hearing loss, including more than 25% of people over 60, and projects that over 700 million people will have disabling hearing loss by 2050 [1]. The Lancet Commission estimates that about 20% of people worldwide have some hearing loss, 62% of whom are over 50 [3]. In the United States, disabling hearing loss affects about 5% of adults aged 45 to 54 and 55% of those aged 75 and over [9].

Vision impairment follows a similar pattern. In 2020, besides the 43.3 million people who were blind and the 295 million with moderate or severe distance vision impairment, 258 million had mild vision impairment and 510 million had near vision impairment from uncorrected presbyopia (the age-related loss of the ability to focus on close objects) [2]. Between 1990 and 2020, the age-standardised prevalence of blindness among adults aged 50 and over fell by 28.5%, but because populations grew and aged, the number of blind people rose by 50.6% [2].

Age-related hearing loss results from the gradual loss of hair cells and nerve fibres in the inner ear, which do not regrow. Noise causes the same kind of permanent damage, and the World Health Organization estimates that over 1 billion young adults are at risk of permanent, avoidable hearing loss from unsafe listening, such as loud music through headphones or at venues [1]. Among US adults aged 20 to 69 who reported five or more years of very loud noise at work, about 18% had hearing loss in both ears at speech frequencies [9].

Most vision loss in older adults has treatable causes. Among adults aged 50 and over in 2020, the leading causes of moderate or severe vision impairment were uncorrected refractive error (86.1 million cases) and cataract (78.8 million), while the leading causes of blindness were cataract, glaucoma (damage to the optic nerve, often from raised pressure in the eye), uncorrected refractive error, age-related macular degeneration (damage to the central retina) and diabetic retinopathy (damage to the retina's blood vessels from diabetes) [7].

Hearing loss is associated with poorer cognition and a higher risk of dementia. In 639 adults in the Baltimore Longitudinal Study of Aging followed for a median 11.9 years, dementia risk rose by 27% for every 10 decibels of hearing loss, and the hazard ratios (risk relative to people with normal hearing) were 1.89 for mild, 3.00 for moderate and 4.94 for severe loss [4]. In a separate analysis of 347 adults aged 55 and over from the same study, the reduction in memory and executive function scores associated with 25 decibels of hearing loss equalled that associated with 6.8 years of age [10]. The Lancet Commission's pooled analysis of 666,370 people found 37% higher dementia risk with hearing loss [3]. The wider set of factors is described under dementia risk factors, and age-related change in thinking under cognitive aging.

Proposed explanations include the extra mental effort of decoding degraded sound, reduced stimulation of the brain's hearing areas, and withdrawal from conversation and social life. Social contact is itself protective: less frequent social contact was associated with 57% higher dementia risk across 19 studies [11], and stronger social relationships with 50% greater odds of survival across 148 studies [12]. Social connection is covered in a separate article.

Treatment evidence comes from observational studies and one large trial. In a pooled analysis of 8 studies with 126,903 participants followed for 2 to 25 years, hearing aid users had 19% lower risk of cognitive decline than people with uncorrected hearing loss [13]. The ACHIEVE trial assigned 977 adults aged 70 to 84 with untreated hearing loss to hearing aids with counselling or to health education. It found no difference in three-year cognitive decline in the whole group, but the effect differed between its two recruited populations [14]; in the older, higher-risk group with more risk factors, hearing aids reduced decline by 48% [3].

Full deep dive: Hearing, vision and the brain.

Untreated vision loss was added to the Lancet Commission's list of dementia risk factors in 2024. A pooled analysis cited by the Commission found 38% higher dementia risk with visual impairment among 37,705 people; among specific eye diseases, diabetic retinopathy and, at the margin of statistical significance, cataract were associated with higher risk, while glaucoma and age-related macular degeneration were not clearly associated [3].

The strongest evidence that treatment matters concerns cataract surgery. In the Adult Changes in Thought study, 3,038 adults aged 65 and over with cataract or glaucoma were followed with data collected from 1994 to 2018; cataract removal was associated with 29% lower dementia risk (hazard ratio 0.71), whereas glaucoma surgery, which does not restore vision, showed no association [8]. The comparison with glaucoma surgery was designed to test whether healthier people are simply more likely to have eye surgery.

Both senses are linked to survival. In 9,885 US adults with hearing tests from national health surveys, followed for a median 10.4 years, hearing loss was associated with 40% higher mortality, and among the 1,863 adults with hearing loss, regular hearing aid users had 24% lower mortality than never-users after adjustment for age, hearing level and medical history [5]. In that sample, only 12.7% of adults with hearing loss used hearing aids regularly [5], and among US adults aged 70 and over who could benefit from hearing aids, fewer than 1 in 3 had ever used them [9].

A pooled analysis of 17 studies with 47,998 participants found that visual acuity worse than 6/12 (seeing at 6 metres what a person with typical sight sees at 12) was associated with 29% higher all-cause mortality, and severe impairment worse than 6/60 with 89% higher mortality in a single study [6]. Vision also affects everyday safety: among 277 older drivers with cataract, those who had surgery were involved in about half as many crashes during 4 to 6 years of follow-up (rate ratio 0.47) [15]. Poor vision is also one of the factors considered in fall prevention, alongside strength and balance training.

Most of the evidence is observational. People who use hearing aids or have cataract surgery may differ from those who do not in wealth, education and contact with health care, which could explain part of their better outcomes; the glaucoma comparison in the cataract study and adjustment for measured factors reduce but do not remove this bias. Reverse causation is also possible, because early cognitive decline can make hearing and vision tests harder and reduce the use of hearing aids.

The only large randomised trial of hearing aids, ACHIEVE, did not meet its main goal in the full group, and its positive result in the higher-risk group comes from a secondary analysis [14]. Hearing loss in many studies is measured once, and some studies rely on self-report rather than audiometry (formal hearing tests). The dementia studies concern adults who lost hearing or vision after a lifetime of typical senses and do not describe people deaf from birth or early childhood.