Guest Blog by Melanie Lewis, RHAD, PCGE – Registered Hearing Aid Dispenser
The Canadian Association of the Deaf estimates that over 3.5 million Canadians are hard of hearing (1). Prevalence rates for hearing loss are largely age related with less than 1% of people under the age of 15 affected. But 75% of those are over the age of 70. Age-related hearing loss (or presbyacusis) highlights a causal link between one’s age. And also the rate of hair cell degradation in the cochlea of the inner ear. In recent years, leading research has identified a link between social exclusion and the progression of dementia. (2) The research by the Johns Hopkins University also underscores a corollary between the effects of unmanaged loss and patterns of reclusiveness.
How We Hear
The process of ‘hearing’ is a complex mechanism. It involves transfer of sound vibration through the outer, middle and inner ear. Any natural or cumulative effect of ageing on the ears tends, as touched upon, to affect the hair cells in the cochlea of the inner ear. The human inner ear contains tiny hair cells which are pivotal in the hearing process. It is the function of these hair cells (cilia) that transform sound vibration into the electrical impulses. Which then can be relayed via the auditory nerve to the brain. The hair cells, which are measured in their thousands, are susceptible to damage from excessive noise (noise induced hearing loss). Prolonged use of certain ototoxic medication, congenital defects and from the natural process of ageing. From as early as one’s mid-40’s natural deterioration of the hair cells occurs.
The culmination of this gradual decline however is not always recognized as discernible hearing deficiency until over the age of 65 years. Unlike many medical conditions, sensory (or sensorineural) hearing loss due to poor hair cell function cannot be reversed. As the body is unable to regenerate or regrow new hair cells. The treatment is centralized around managing rather than curing the loss. Increasingly, leading institutions, such as Harvard University(3) are exploring the possibilities of stem cell research. In a bid to regenerate those dead or damaged cells. By mimicking, it is hoped that the natural regeneration which birds are able to do spontaneously. Whilst successful stem cell regeneration has not been demonstrated in a human ear, if achieved it could certainly be the ‘cure’ for a condition that can yet only beameliorated.
Unmanaged Hearing Loss and Dementia
According to a study in 2011 by Frank Lin, M.D., an otolaryngologist and epidemiologist at Johns Hopkins School of Medicine in Baltimore. Those with unmanaged hearing loss were seen to be at an increased risk of developing dementia and loss of cognitive function. The study further posited that socially isolated individuals were also more likely to develop the condition. Of 639 participants, studied over a period of 18 years. The researchers found that those with hearing loss at the beginning of the study were significantly more likely to develop dementia by the end. Staggeringly, for individuals with a severe degree of hearing loss. The risk was seen to increase by as much as fivefold.
For individuals with unmanaged hearing loss the effort expended in trying to ‘hear’ is inordinate. The subconscious ability to follow the pace and nuances of conversation. Is denied for those who are affected, which many of us usually take for granted. The need to focus solely on the sound source, whilst trying to filter extraneous noise. The need to use basic lip-reading skills and the fear of substituting or mis-interpreting the thread of conversation is a constant worry. It is little wonder that for many it is actually easier to refrain from social discourse altogether.
The Johns Hopkins School of Medicine recognises a symbiosis between the cognitive strain placed on the brain for those with unmanaged hearing loss. And by proxy, the reaction which it often engenders – social withdrawal. Whilst the study does not suggest that unmanaged hearing loss is the direct cause of dementia. It does appear to be a risk factor for propagation of the condition.
Managing Hearing Loss
As touched upon, sensory hearing loss cannot be cured but rather managed. Remediation of age-related hearing loss often uses amplification to stimulate residual hair cell function. And where possible, try to restore ‘normal’ loudness perception. The initial hearing test, or screening process, is fundamental in establishing the degree of loss against a normative value and assessing the best intervention strategy. Whilst hearing aids are perhaps the most popular ‘treatment’ option they often work well alongside other assistive listening devices. It can be whether volume-enhanced telephones, TV listeners or amplified alarms. For individuals reticent to acknowledge or address possible deficits in their hearing then family members and caregivers may be crucial in preventing social withdrawal. Access to routine hearing checks can often be facilitated by an external support network. And can mark the difference between early intervention, securing continued social discourse, or left unmanaged, marked auditory and cognitive struggle later on.
Melanie Lewis, RHAD, PCGE is a qualified Registered Hearing Aid Dispenser who worked for many years at H.S Audiological Centres before moving to head up HearingDirect audiology department in 2012.
Reference:
(1) According to The Canadian Association of the Deaf.
(2) According to the Johns Hopkins University.
(3) According to the Harvard University.
