November 2016

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The relationship between hearing loss, cognitive ability and cognitive decline is receiving significant attention among medical researchers around the world. As the third most common chronic health condition affecting older adults, hearing loss affects about 30% of patients 65 and older and as much as 70-90% of those 85 and older. Basic cognitive skills like working memory, the ability to focus on a speaker in a noisy background or process information quickly, also decline with age. The Alzheimer’s Association reports that 5.1 million people over 65 have Alzheimer’s, the main type of dementia affecting memory and cognitive processing skills and accounts for the sixth leading cause of death in the U.S.

The processes involved in cognition, language and audition are tightly interwoven and interdependent. Hearing can be defined as the perception of sound where listening requires active brain involvement in which meaning is applied to the sound. Understanding speech involves more cognitive ability than just responding to pure tones, though. Attention, inhibition, and executive function, for example, are all required for listening and comprehension of speech. The ability to react appropriately to spoken dialogue also involves using perceptual-motor skills, another cognitive function.

Untreated hearing loss can interfere with cognitive abilities due primarily to the large expenditure of mental effort toward understanding speech. New evidence shows that cognitive decline is more prevalent in elderly people with hearing loss than in those without hearing loss.

In 2013, Frank Lin, MD, PhD, reported in the Journal of the American Medical Association (JAMA) that hearing loss is independently associated with accelerated cognitive decline. Those with hearing loss showed a 30-40% faster cognitive decline than those without hearing loss. The researchers also report that the levels of reduced brain functioning were directly related to the amount of hearing loss.

Two more studies published in the past year not only echo Lin’s findings but also show that treating hearing loss with the use of hearing aids can attenuate that cognitive decline:

A 25-year study published in the Journal of the American Geriatrics Society in 2015 concluded that people with untreated hearing loss had significantly lower scores on the Mini-Mental State Examination (MMSE), a well-established test of cognitive function. They also found that hearing aid use mitigates that cognitive decline.

In a study published in February 2016, Jamie Desjardins, PhD at The University of Texas at El Paso speech-language pathology program shows that hearing aids do improve brain function in people with hearing loss. Desjardins studied a group of 50-60 year olds with bilateral sensorineural hearing loss who had previously never used hearing aids. After two weeks of hearing aid use, tests revealed an increase in percent scores for recalling words in working memory and selective attention tests, and the processing speed at which participants selected the correct response was faster.

Cognitive decline, age-related vision loss, poor motor skills and decreased health literacy are often associated together and patients with cognitive impairment often have deficits in these other areas as well. This can affect how patients understand and incorporate medical instructions and treatments into their lives. Compounding the issue, too, is that symptoms of hearing loss can overlap with those of dementia. In combination with cognitive screening tools like the Mini Mental Status Examination (MMSE), the Clock Drawing Test (CDT), the Mini-Cog Test and the Montreal Cognitive screening assessment (MoCA), thorough hearing evaluations by an audiology specialist support a comprehensive care model to identify hearing needs. Because of the known negative consequences of untreated hearing loss on health and well-being, the National Council on Aging also encourages primary care providers to incorporate hearing loss discussions into routine exams.

Reducing the mental load of understanding speech through better hearing is an important step in liberating more cognitive capacity for other brain functions. However, proper hearing rehabilitation is a complex process and involves more than just using hearing aids. Pathways like shared neuropathic conditions, cognitive load, and social isolation likely contribute to accelerated cognitive decline in people with hearing loss. While new studies are showing improved cognitive function by treating hearing loss with hearing aids, further research is needed to understand how these multiple pathways respond to hearing rehabilitation interventions. “As hearing changes, so do communication ability, cognitive function, and psychological factors…affecting quality of life and the whole person, not just hearing.” A network of specialized providers, including hearing healthcare professionals supports improved health and lifestyle for hearing impaired patients.

“Hearing loss was recently qualified as a risk factor for accelerating brain aging by reducing brain volume and cognitive abilities”