A recently published Lancet Commission (2017) into dementia prevention, Hearing loss when you’re young could lead to dementia when you are old; intervention and care concludes that around 35% of dementia is attributable to a combination of nine modifiable risk factors, including education to a maximum age of 11 to 12 years, midlife hypertension, midlife obesity, hearing loss, late life depression, diabetes, physical inactivity, smoking and social isolation. The Lancet Commission suggests that early intervention for hearing loss in midlife has the potential to improve cognitive resilience and possibly delay the onset of cognitive decline and dementia.
The recognition of hearing loss and social isolation as modifiable risk factors for dementia is relatively new. While research suggests a correlation between hearing loss and risk for dementia, the exact process is still not not understood. As sensorineural hearing loss is often insidious, many people incorrectly attribute it to the inevitable consequence of aging and regard it as innocuous. The diagnosis of sensorineural hearing loss is often met with viewpoints such as, “My hearing is not that bad”, “My hearing is still good for my age” or “I am too young for hearing aids”, which delays intervention. Research suggests that hearing aid wearers wait on average between 7 and 10 years before seeking help for hearing loss.
While many people feel that they can “cope” with hearing loss, research by Frank Lin and his team suggests that “coping” comes at a significant cost in terms of cognitive real estate. In one study, analysis of MRI in Lin’s research showed accelerated rates of brain atrophy for participants with hearing loss compared to those with normal hearing. Overall, study showed that those with impaired hearing lost more than an additional cubic centimetre of brain tissue each year compared with those with normal hearing. Those with impaired hearing also had significantly more shrinkage in particular regions, including the superior, middle and inferior temporal gyri, brain structures responsible for processing sound and speech. The middle and inferior temporal gyri, also play roles in memory and sensory integration and have been shown to be involved in the early stages of mild cognitive impairment and Alzheimer’s disease.
Based on my clinical experience, I have little doubt that the deprivation of sound to the auditory cortex and brain atrophy makes adjusting to hearing aids challenging. Despite excellent advances in technology, hearing aids cannot provide the “quick fix” that many are hoping for, since the brain needs to rewire itself to adapt to the new sound through amplification. Often the brain has been deprived of sound for a period of ten or more years before hearing aids are prescribed.
In my experience, hearing loss appears to be a taboo subject for many people in late life, so providing intervention in midlife poses a significant challenge to how people view hearing loss with regards to general health. Successful intervention for hearing loss to build cognitive resilience will depend on making hearing screenings a routine part of medical care in their 40’s and 50’s. In my clinical experience, many patients will have their first hearing test in their late 70’s or early 80’s. While people are accustomed to routine medical checks for cholesterol, blood pressure and eyesight, most of us haven’t had a hearing test since primary school! Including a hearing screening in your annual health check will help to optimise your brain’s health.