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Hearing: Can You Hear Me Now?
Hearing loss at any age impacts mental and physical well-being.


BY GUY FIORITA

May 2018



According to the National Institute on Deafness and Other Communication Disorders, one in 1,000 infants is born totally deaf, while as many as six per 1,000 are born with hearing loss of different levels. This makes hearing loss one of the most common birth disorders in the United States. At 18 or older, approximately 15 percent of Americans report some trouble hearing, and the older we get the worse it gets, with nearly 25 percent of those ages 65 to 74 and 50 percent of those 75 and older have disabling hearing loss.

Researchers now know that a loss of hearing causes physiological changes in the brain and can have profound psychological effects. We asked Dr. Stacy Ryan, senior clinical audiologist at the UW-Milwaukee Audiology Group, how hearing loss affects the brain at various stages in life, from early development through old age.

M: What effects does a hearing impairment have on infant development?

Dr. Ryan: Although not fully mature, a fetus is able to process sound at 25 weeks gestation. Studies have shown that infants with typical hearing recognize their parent’s native language at birth. As a result, infants with congenital hearing loss are born with delayed auditory systems. The hearing loss causes a lack of input to the neurological system. Without stimulation, the nerves intended for auditory processing will reallocate themselves or die off as a natural pruning process occurs. 

A baby’s brain doubles in size during the first year of life and by three years it is approximately 80 percent of its total adult volume.  Additionally, a child has more neural synapses at age 2 than any other time in their lives. Repeated exposure to certain meaningful sounds strengthens neural pathways. Synapses that are rarely or never utilized will eventually be pruned. After age 3, the central auditory nervous system is hardwired based on the experiences it is provided. Without proper stimulation, the auditory brain is not provided adequate input and it becomes an uphill battle to rewire the brain and reach optimal performance. It is during this time of critical neurological development that language stimulation is crucial.

Psychologically, untreated hearing loss can negatively impact an infant’s connection to caregivers, especially when you consider that over 90 percent of children with hearing loss are born to typically hearing parents who will communicate with their child through spoken language. In short, untreated hearing loss causes delays in receptive and expressive communication skills. 
 

M: How are children affected by hearing loss?

Dr. Ryan: Children are slower at processing auditory sounds/auditory speech and don’t find it as easy as adults to fill in gaps of sounds they missed. Additionally, children depend on hearing for incidental learning.  Your parents probably never taught you how to answer a telephone. You watched them and learned to pick up the phone, bring it to your ear and say “Hello.” Actual first-graders were given portions of common colloquial phrases and asked to complete them. The result was something like this: “Better to be safe than ... punch a fifth-grader” and “Don’t bite the hand that ... looks dirty.”

As adults, with mature auditory systems, we don’t even need to hear the last portion of these phrases, yet our brains will fill in the blanks. Children lack the neural redundancy and experiential knowledge to do the same. When a hearing loss causes more gaps in the speech signal, there become too many blanks to fill in and a communication breakdown occurs. Psychologically, language deficits can cause learning problems that may result in reduced academic success. Furthermore, communication difficulties can result in social isolation and low self-esteem.


M: When do people begin to lose their hearing?

Dr. Ryan: Research suggests the auditory brain begins seeing a decline in processing speeds as early as 38 years of age, even in the absence of peripheral hearing loss. The first signs of this are increased difficulty understanding speech in background noise, difficulty understanding speech without visual cues, difficulty understanding rapid speakers and finding background noise more distracting and tiring. Studies have shown that hearing loss impacts financial and vocational success. Hearing loss in adults is an additional stress on an already busy life. Any activity that involves communication is impacted. Anger, denial, anxiety, depression, withdrawal, stress, fatigue and social isolation have all been linked to adults with hearing loss.
 

M: Statistics show that 50 percent of people over 75 have hearing loss. What causes this and how does it affect their quality of life?

 Dr. Ryan: As a person ages, their auditory processing time will further reduce and they will either begin to develop hearing loss or the hearing loss will progress due to neural presbycusis. Physiologically, this includes hair cell damage within the cochlea, damage to the VIIIth cranial nerve (auditory nerve) and reduced neural impulses through the central auditory nervous system. Psychologically, hearing loss and reduced processing speeds causes isolation in the elderly. Family gatherings can be noisy, leaving the elderly adult acoustically isolated. There is a very strong correlation between hearing loss and depression in older people and it appears to speed up age-related cognitive decline. Without proper auditory stimulation, brain tissues deteriorate. Pivotal studies conducted at Johns Hopkins (University) have correlated dementia and hearing loss and initiated a frenzy of research in this area.







 

This story ran in the May 2018  issue of: