Presbyacusis

Synonyms: Age-related hearing loss, presbycusis, presbyacusia, presbyacousia, senile deafness (latter term discouraged due to its negative connotations).

This is a progressive, usually bilateral, sensorineural hearing loss that occurs in older people as they age. It is a multifactorial process driven by environmental factors and exacerbated by concurrent disease.¹ The word may be used as an umbrella term to cover all causes of diminution of hearing in the elderly.

It can range from bothersome to severely disabling in its effects on the sufferer. In moderate to severe cases it can cause the older person to become isolated, depressed and may significantly worsen age-related disability/cognitive impairment and dementia.² Additionally, while loss in peripheral hearing sensitivity explains many of the listening problems of elderly persons, some studies suggest that age-related declines in general cognitive skill and central auditory processing also appear to contribute.¹

It is eminently correctable using rehabilitative measures and its successful treatment can vastly improve quality of life for the older patient. Unfortunately, it is not a fashionable or socially appreciated problem meaning that it is largely unrecognised and undertreated in the older population at large. Screening by elderly care specialists and primary care physicians, with referral for appropriate therapy, can make a positive and tangible difference to the lives of older people.

You may find our record on Deafness useful, with information on examination, an overview of treatment options and managing a consultation with a deaf person. You may also find our record on Tinnitus relevant.

Loss of cochlear outer hair cells, ganglion cell loss in vestibulocochlear nerve fibres and atrophy of the highly vascular stria in the lateral cochlear wall (thought to be the most important factor) all contribute to the process. Stiffness of the cochlear basilar membrane (cochlear conductive deafness) was considered to contribute but is now thought to be of minor relevance. It is not ageing of itself that causes the problem, rather the effects accumulated environmental noise toxicity and metabolic/oxidative stress. Degenerative central nervous mechanisms (central presbycusis) can cause poor speech discrimination in some individuals (~10%) but is unusual in isolation and difficult to distinguish from peripheral causes. Central presbycusis may still be improved by treatment aimed at peripheral mechanisms.

Prevalence

The vast majority of the UK's 9 million deaf or hard of hearing population have developed hearing loss over time. After 50 years of age, the incidence of deafness rises sharply - 55% of the over 60 year old population have some degree of hearing impairment.⁴ About 80% of cases of significant hearing impairment occurs in this age group.^5,6 The vast majority of people aged over 70 will have some degree of objective hearing impairment or subjective worsening compared to their youth.⁷ The effect of noise pollution means that hearing loss is more prevalent among older people in industrialised compared to agrarian societies.³

Risk factors

• Exposure to industrial/urban/armament noise without ear protection⁸
• Ototoxic medication e.g. aminoglycosides, cisplatin, loop diuretics, NSAIDs³
• Family history/genetic factors (mitochondrial DNA mutations and exposure to oxidative stress are thought to be relevant)^9,10
• Hypertension³
• High cholesterol¹¹
• Diabetes¹²
• Smoking⁸
• High body mass index⁸

It is unclear whether these factors act in specific, pathological ways or whether they accelerate an underlying process.¹ Interestingly, moderate alcohol consumption has been found to be inversely correlated with hearing loss.⁸

Symptoms

Problems are often first noted in noisy environments; there is usually a slow, insidious onset of symptoms with gradual progression. However, some people may feel their hearing has suddenly worsened due to crossing a 'threshold' where the symptoms become noticeable. (It is also known that the rate of hearing decline is a highly variable, non-linear process).¹

The ability to understand speech is often the earliest symptom as high frequency hearing loss predominates.¹ It may be the patient's friend/relatives who note the problem, rather than the sufferer. Discrimination of the voiceless consonants (t, p, k, f, s and ch) becomes difficult as the condition progresses (patients may complain of others mumbling). Patients complain that they cannot understand what is being said rather than of an inability to hear. Words like 'mash', 'math' and 'map' become indistinguishable. Patients can usually manage a one-to-one conversation but struggle when there is more than one speaker and when there is background noise.

When assessing elderly patients with depression or cognitive impairment, hearing loss should be directly asked about and considered as a cause of the symptoms. Tinnitus may be a feature of presbycusis when the hearing impairment becomes marked and should be directly asked about. It can be very disturbing and disabling.

Signs³

There are no definitive signs of presbycusis. Auroscopy may reveal wax (cerumen) accumulation. 10% sodium bicarbonate drops will help to dissolve this and may improve symptoms, when reassessment can take place. Opacification of the tympanic membrane is a normal feature of ageing and does not affect the acoustic efficiency of the ear.

Presbycusis is a diagnosis of exclusion and should not be made as a blanket diagnosis in the elderly person with hearing loss until other possible causes have been considered and excluded/thought unlikely. Consider:

• Wax (cerumen) impaction
• Hearing loss due to cerebrovascular disease
• Otitis media (acute or chronic suppurative)
• Benign tumours of the middle ear
• Cholesteatoma
• Noise-induced hearing loss
• Other granulomatous or inflammatory disease of the middle ear
• Otosclerosis
• Acoustic neuroma
• Infection/tumours of the petrous temporal bone
• Autoimmune disease of the middle ear
• Perilymphatic fistula

It is a good idea to conduct screening for presbycusis in patients aged over 60. Asking "Do you have a hearing problem?" on new-patient questionnaires or during health checks for older people is a very cost-effective and sensitive instrument to screen for this condition. It has been shown to be more sensitive than more complex screening questionnaires.¹³

Clinical spoken voice and finger friction tests may be considered¹⁴ but some claim that these are imprecise and ineffective. Use of audiometry to screen patients and/or confirm the diagnosis is very effective and modern equipment is easy-to-use, cost-effective, lightweight, well-accepted by patients and can be easily used in a community setting. Testing should be carried out at frequencies of 1, 2 and 3 kHz at intensity levels of 25, 40 and 60 dB. Failure at any frequency at 25 dB for younger adults or 40 dB for those aged 60 and over justifies referral for definitive assessment.

Further investigation such as neuroimaging is not required unless there are clinical reasons to suspect an underlying pathology e.g. unilateral or significantly asymmetric hearing loss or troublesome tinnitus out of keeping with the severity of hearing loss on the audiogram. Tests for diabetes, renal impairment, hypertension or dyslipidaemia are worthwhile in individuals who have not been checked recently for these problems.

1. Communication courtesy and environmental noise manipulation - those communicating with older patients should take care to speak face-to-face in a clear and unhurried manner. Sufferers should be encouraged to voice difficulties with misheard phrases and ask for clarification. If possible, there should be a clear explanation of the problem to family and friends.
2. Reassurance and education - patients often find it very reassuring to know that they will not go completely deaf. It has been shown that proactive communication education programmes have an important role to play in the management of these patients. This may be as an adjunct to - or even replace - more traditional interventions (e.g. hearing aid fitting - see below).¹⁵
3. Amplification - usually indicated when average hearing thresholds reach 40 dB on audiogram but lesser hearing loss can still benefit. Aids are available both on the NHS and privately; privately sold aids are not necessarily better than those obtained on the NHS.
   • There is a staggering variety of hearing aids using analogue or digital amplification; currently, it appears that digital aids are superior.
   • There are ongoing advances in directional microphones and noise-suppression circuitry which continue to improve performance.
   • Hearing aids have problems about which patients should be counselled: normal hearing is not restored, it takes time to learn to use and adapt to one optimally, they can be uncomfortable or cosmetically undesirable and they are expensive. However, they remain the mainstay of managing presbycusis and are particularly helpful to those with severe hearing loss.
   • Patients should be encouraged to persevere if background amplification is annoying as they will adapt to this. Intermittent use because of this problem prevents central adaptation and should be advised against.
   • Good education about hearing aid use maximises their benefits.
4. Speech reading - use of facial visual cues and study of lip movements aids understanding of speech. Formal training in these skills may be difficult to come by.
5. Auditory training - structured learning to help recognise speech sounds and key words with amplification. This takes some effort and training centres are thin on the ground.
6. Assistive listening devices - frequency-modulation transmitters, amplified telephones, teleconnectors for hearing aids/phones and other ingenious devices can make a big difference to people's lives. Hearing dogs are also used.
7. Cochlear implants - these are indicated for any patient, regardless of age, who has bilateral severe hearing loss not materially improved by hearing aids.³ The older patient will probably do well due to good language skills and relatively short duration of deafness.

Untreated presbycusis leads to social isolation, depression and may cause or worsen cognitive impairment and dementia.^1,2,3

The stereotypical image of old age as an inevitable decline into severe deafness is not warranted. Early identification and management of presbycusis can significantly improve the lives of older people and help to change this picture.

Some sensory presbycusis is inevitable but avoiding noise exposure and using ear protection in noisy environments will prevent progressive damage. Younger patients should be informed of the danger of repeated and prolonged noise exposure in clubs/at music events. Good diet, general health and fitness can reduce cardiovascular contribution to hearing loss.³ The role of anti-oxidants in the management and prevention of hearing loss is still being investigated but a recent review suggests promising results for the future.¹⁶