How smell relates to hearing

Jul 6 2023

In 2021 Dr Rachel Herz surveyed over 400 people about how highly they valued their sense of smell, compared to a whole range of other things.

One surprising revelation was: about 20% of people would rather give up their sense of smell, than their mobile phone.

However when you talk to people who did lose their smell when they got COVID, they will tell you they have a new found appreciation for it.

Hearing is related to smell - a comprehensive Japanese study on the Relationship between tinnitus and olfactory dysfunction showed some interesting correlations. Using your senses, be it hearing, smell or site have a dramatic effect on how you age.
We have seen anecdotal evidence of the decline in cognitive function in people with hearing loss. Refer our article: Ageing, Hearing Loss, Dementia and Hearing Care.

Methods used in the hearing smell comparison

Sensory tests including hearing and visual examinations were conducted with 510 individuals (295 women and 215 men) in Yakumo Japan.

"The participants completed a self-reported questionnaire on subjective tinnitus, olfactory function, and hearing function, as well as their lifestyle. The health check-up included smell, hearing, vision, and blood examinations."

Read some of the latest research on Tinnitus

Results of the comparison

"After adjusting for age and sex, the presence of tinnitus was significantly associated with subjective olfactory dysfunction, poor olfactory test results, hearing deterioration, vertigo, and headache."
"Subjective smell dysfunction and poor smell test results were significantly associated with tinnitus complaints."

Developing your sense of smell

Professor Thomas Hummel suggests there is a link between the sense of smell and experiences of depression.

He also conducted a study where some participants in their 70s did smell training for six months to strengthen their ability to smell things, while other participants did Sudoku tasks.

"We asked people about the cognitive age how they felt, and they said they would feel on average like six years younger."

Dr Rachel Herz:
There are neurological diseases like Alzheimer's and Parkinson's disease that are very much connected to smell function and losing your sense of smell. It is often decades before other symptoms appear. The first warning sign of the fact that this is happening to you. And so if you are, let's say, from the age of 40 onward, you really should be paying attention to how well you can smell and if you suddenly notice that or other people are noticing that you aren't able to detect or identify smells, well, then you should potentially get neurologically checked. But in addition to that, maintaining healthy cognition, just maintaining good memory, good thinking skills, good sort of whole functioning of your brain, especially as we get older is very much tied to having a good sense of smell. And this seems to be basically part of the whole neuroplasticity story where the more activation you have, the more input you have from your environment, the better your brain health and your cognition is going to be overall.

Odor recognition and identification, and in particular its failure, is a critical factor in human health. Data from a representative sample of over 3000 US community dwelling adults 57 years and older, recently revealed that those who were dysfunctional at odor identification were four times more likely to die within a five year period than their same age peers with normal olfactory abilities. Impairment of odor identification is also a hallmark early symptom and predictor of several neurological disorders, most notably Alzheimer’s disease and Parkinson’s disease."

Emotions and smell

The relationship between smell and emotions is quite clear. Think of the smell of coffee. This association is believed to be due to the parts of the brain that analyse smell, sit very closely to the parts of the brain associated with memory formation, and the processing of fear. It's a very direct anatomical connection and explains the very clear effects that the sense of smell has on our emotions.

In addition to links between smell, memory, and good and bad emotional reactions, researchers also believe there may be an association between a good sense of smell and good cognitive function.

Good cognitive function is a requirement to hear well in your later years. It is often the processing power of your brain that determines how much of a conversation you process. Even with hearing aids people who have a declining cognitive function do not appear to hear as well due to their lack of processing power.

"There's a direct pathway between smell, and emotion. So the smell sensors are located behind our nose, and the Amygdala is behind that again, and the Hippocampus is behind that again. So whilst most sensory modalities go to the Hippocampus first and then the Amygdala, Smell goes in the opposite direction.