It’s All In Your Head: Save Your Hearing and Help Save Your Brain
Did you know that at least 40–50% of adults over the age of 65 years have a measurable hearing impairment? This figure rises to 83% of those over the age of 70 years. This means that hearing loss is the third most prevalent chronic medical condition among older adults, after arthritis and hypertension.
Beyond the obvious impediment to spoken communication, we have come to realize that there are also hidden effects of hearing loss that may have significant consequences on brain health especially in preventing dementia. The usual reason for worsening hearing in aging is the loss of microscopic hair cells located in the cochlea in the inner ear. There are some 12,000–15,000 outer hair cells that are caused to move in response to sound. This serves as a tiny amplifier, that changes the mechanical vibrations into electrical nerve impulses that reach the sound reception areas of the brain. There is a very large part of our brain on each side devoted to interpreting sounds.
Most age-related hearing loss (presbycusis) is a loss of hair cells in the region of the inner ear that is responsive to the high-frequency sounds. These sounds are critically important for the perception of speech. As many older adults know only too well, associated with loss of high-frequency sounds also comes an increased difficulty in hearing speech in the presence of background noise. Common instances of this include the noise of traffic, the babble of multiple conversations in a crowded restaurant, and situations when the acoustic ‘noise’ consists of two people talking at once.
Research has shown that in such a situation like a crowded restaurant, hearing the conversation actually requires effort. The brain has to work hard to figure out what is being said and this steals away our awareness and enjoyment of the situation. Researchers have found that this type of ‘effortful listening’ is associated with increased stress responses, changes in pupil dilation, and poorer behavioral performance. Many of us resort to “tuning out” and sitting quietly just nodding our heads hoping nothing really important was being discussed.
The connection between hearing acuity and mental clarity may go beyond the effects of stress under conditions of effortful listening. A striking finding from a recent large-scale population study has revealed a strong connection between the degree of hearing loss and the development of dementia. One large study showed that in elderly people with hearing loss, there was actually a decrease in brain size as measured by volume on MRI testing.
Additionally, people with hearing loss are more likely to avoid social situations, which may impact both physical activity and emotional wellbeing; any of which may mediate the relationship between hearing ability and brain health. We use our ears to collect sound, but we listen with our brains. Providing the best hearing possible from the ear to the brain is one aspect that both ENT doctors and Audiologists focus on.