Hearing loss in later life clearly affects the ability to listen and communicate. However, we now know that hearing loss also accompanies a decline in cognition — for example, difficulty remembering things, difficulty controlling our thinking, and difficulty using words or language. Alarmingly, research over the last 15 years has shown that hearing loss raises the risk for dementia and mild cognitive impairment (Livingston et al. 2020, The Lancet 396(10248):413-46). In other words, you are more likely to be diagnosed with dementia if you have lower hearing ability in mid- to late-life. No current research has definitively found that hearing loss causes dementia (risk in the medical jargon does not mean a causal effect), but their coincidence is well-established. Research is required to better understand the link between hearing and cognition, especially if treatment of hearing loss is a viable strategy to delay or avoid age-related cognitive decline.
Why is hearing loss related to cognitive decline? There are several competing explanations, or hypotheses, for why hearing loss and cognitive decline are related. Perhaps there is a common cause that leads to decline in both hearing and cognition, such as poor cerebral blood flow. Other researchers reason that social isolation due to hearing loss could lead to cognitive decline, because if people withdraw from others due to listening problems, thinking and remembering may get worse.
A final explanation considers the demand that hearing loss places on our brain’s capacity to deal with complexity of everyday life. When a person has hearing loss, the act of listening alone consumes many “cognitive resources,” or the limited ability we have to understand things in our environment and meet our goals. This is because the auditory signals that the person receives are strongly degraded, and listening thus requires more concentration. If too few resources are left over, then we can’t perform other tasks that are important in everyday life. For example, a person with hearing loss may have problems remembering what someone said, because they were too concentrated on just the act of listening. Even worse, depleted resources can impact our abilities in other senses. Consider a situation when a person is operating a motor vehicle. If a person with hearing loss is trying to understand what a passenger is saying, then it may become more difficult to coordinate their hands, feet, and eyes to safely drive a car.
What can we do? Currently we are collaborating with Rotman Research Institute, a world-renowned facility for aging and health care, to do research on cognitive decline in hearing. We are using EEG and behavioural testing to understand how long-term memory processes are affected by aging. Stay tuned as this exciting collaboration develops.
Example publications on hearing and cognitive ability
Paul, B. T., Chen, J., Le., T., Lin, V. & Dimitrijevic, A. (2021). Cortical alpha oscillations in cochlear implant users reflect subjective ratings of listening effort during speech-in-noise perception. PLoS ONE 16(7): e0254162. doi:10.1371/journal.pone.0254162
Prince, P., Paul, B. T., Chen, J., Le., T., Lin, V. & Dimitrijevic, A. (2021). Neural correlates of visual stimulus encoding and verbal working memory differ between cochlear implant users and normal-hearing controls. European Journal of Neuroscience, 54 (3), 5016-5037. doi:10.1111/ejn.15365
Paul, B. T., Uzelac, M., Chan, E., & Dimitrijevic, A. (2020). Poor early cortical differentiation of speech predicts perceptual difficulties of severely hearing-impaired listeners in multi-talker environments. Scientific Reports, 10:6141. doi:10.1038/s41598-020-63103-7
Paul, B. T., Bruce, I, C., Bosnyak, D. J., Thompson, D. C., & Roberts, L. E. (2014). Modulation of electrocortical brain activity by attention in individuals with and without tinnitus. Neural Plasticity, vol. 2014, Article ID 127824. doi:10.1155/2014/127824.
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