Hearing loss, a pervasive health epidemic today, not only impacts hearing ability but also brain health. The auditory system which refers to how we hear and understand sound involves both the ears and the brain. Hearing loss is a chronic medical condition that results in difficulty absorbing sound and also processing (and making meaning) sound. This can impact the brain in a variety of ways including contributing to the development of cognitive decline. The most effective way to mitigate brain health risks is to treat hearing loss which supports cognitive function.
Hearing Loss & the Brain
Hearing involves parts of the brain including the auditory cortex which process speech and language. Hearing loss impacts these areas which can lead to various health risks. In a 2015 study, researchers in the Department of Speech Language and Hearing Science at University of Colorado investigated how the brain responds to hearing loss. The study involved taking electroencephalographic (EEG) recordings of adults and children with various degrees of hearing loss. EEG testing consists of playing small sensors around the scalp which enables researchers to evaluate brain activity in response to stimuli. In this study, participants experienced sound stimulation in the form of recorded speech syllables (played from speakers) and researchers tracked their brain activity in response.
Two key findings from this study are that adults with hearing loss, compared to those without, experienced:
- decreased activity in the hearing portion of the brain
- brain reorganization in areas responsible for processing visual patterns
This kind of reorganization, or neuroplasticity, describes the changing of neural networks in the brain. In adapting to hearing loss, the areas of the brain that process sound are weakened so other parts of the brain try to compensate. As Dr. Sharma, one of the authors of the study, describes, “the hearing areas of the brain shrink in age-related hearing loss. Centers of the brain that are typically used for higher-level decision-making are then activated in just hearing sounds. These compensatory changes increase the overall load on the brains of aging adults”. This then decreases the brain’s available energy and resources which can produce consequences including dementia.
There is extensive research that highlights the link between hearing loss and cognitive decline. A major study includes the 2019 research conducted by Brigham and Women’s Hospital and Harvard Medical School. This study, published in Journal of Alzheimer’s and Dementia, involved researchers analyzing self-reported hearing loss and cognitive decline over an 8 year period for over 10,000 people. They found that for people with hearing loss, compared to those without, the risk of cognitive decline) was:
- 30% higher among men with mid hearing loss
- 42% to 54% higher among men with moderate or severe hearing loss
These findings reveal a significant correlation between hearing loss and cognitive decline. Researchers suggest that cognitive overload and the ways in which hearing loss reorganizes the brain can lead to declining cognitive function(s).
Treating Hearing Loss & Improving Brain Health
Treating hearing loss can drastically improve hearing ability which positively effects the brain. The most common treatment for hearing loss is hearing aids. These are electronic devices that are designed to absorb, amplify, and process sound; providing the brain with critical support. Research shows that hearing aids mitigate cognitive decline by improving brain function. This includes two recent studies:
- 2020 Study Published in Science Daily: researchers at the University of Melbourne investigated the impact of hearing aids on the brain. The study involved assessing the hearing and cognitive capacity of nearly 100 participants (aged 62-82) before the use of hearing aids and 18 months after using hearing aids. Findings included:
- “97% of participants showed either clinically significant improvement or stability in executive function (mental ability to plan, organize information and initiate tasks)”
- 2018 Study Published in the Journal of American Geriatrics Society: examined data on the cognitive function of hearing aid wearers. The population consisted of over 2,000 people. Based on results from memory tests, researchers found that hearing aid use improved scores and concluded that hearing aids can be an effective intervention in the trajectory of cognitive decline.