Lost in a World Without Scents: The Hidden Danger of Prolonged Anosmia After COVID-19

The human sense of smell may have more utility than just “sniffing.” The book focuses on olfaction and olfactory disorders, which have recently been actively studied in fields such as brain science, and presents the potential. “Not being able to smell” could tell us more about our brains.

Some people lose their sense of smell. In fact, many people have reported loss of smell as a side effect during the COVID-19 pandemic. In some cases, symptoms return quickly, but in other cases, these symptoms persist for a long time. It is often considered a secondary symptom to pain such as cough, fever, shortness of breath, or headache, but if you look closely, it could be a sign of a larger illness.

In a 2019 study, the author, a physician, neuroscientist, and professor of anatomy at the University of Quebec in Canada, found that among those who had olfactory disorders for 6 to 12 months and recovered their function, many patients suffered from depression or anxiety disorders. The author is investigating the hypothesis that there may be a link between smell and depression, not simply for psychological reasons, but due to damage to the brain center. Human emotions and olfactory information are processed together in the limbic system, the oldest part of the brain. If this area is damaged due to a concussion, etc., you may not be able to smell and may also develop depression and anxiety disorders. The author predicts that if this hypothesis is proven, there will be the possibility of determining the risk of depression early through an olfactory test.

The author also notes that the deterioration of the sense of smell can be a sign of Alzheimer’s disease or Parkinson’s disease. It is said that over 90% of these neurodegenerative diseases, which progress without obvious symptoms, are accompanied by olfactory disorders in the early stages. The exact cause of both diseases has not been revealed and it has been reported that protein deformation occurs in nerve cells. Since the disease cannot be completely prevented or cured, early diagnosis is important and the sense of smell can be an indicator.

Of course, there are various causes of smell impairment. Just because you have a sense of smell, you don’t necessarily suspect Alzheimer’s or depression. In fact, the damage to brain and nerve cells is serious and is most often caused by diseases of the nasal mucosa such as rhinosinusitis. In some cases, such as COVID-19, the sense of smell is affected by a viral infection. However, the author says, “the loss of smell can be seen as an ‘early warning symptom’” and “not only helps in the early diagnosis of diseases, but also helps in understanding how these diseases develop.”

In addition to research on olfactory disorders and diseases, the author covers various characteristics of smell that have a significant impact on human evolution, memory, and behavior. Furthermore, just as a sommelier distinguishes wine through aroma and taste, the sense of smell can also be trained through training. We also introduce the interesting fact that their entorhinal cortex is thicker than that of ordinary people. It is also noted that humans, who are omnivores, perceive the scents of fruit better than dogs, who are carnivores, and have a better ability to interpret odors.