Anosmia, or the loss of sense of smell, has been brought to the forefront by the Covid-19 pandemic, affecting thousands of individuals and highlighting the importance of our olfactory system. Researchers are now working to better understand the causes of anosmia in order to improve treatments.
The sense of smell, often mistakenly viewed as a secondary sense in humans, is actually omnipresent and essential for our safety and pleasure. Every time we inhale, we sample odor molecules from the environment to detect potentially interesting odorous objects that may impact our protection, diet, or social interactions. Smells also have a strong emotional and affective component.
Various studies have estimated that between 5 and 20% of people worldwide experience olfactory disorders. In France, a study conducted by the CNRS in 2015 revealed that around 10% of the population, more than 6 million people, have olfactory deficits. These disorders can manifest in different ways, ranging from total loss of smell (anosmia) to partial loss (hyposmia) or even heightened sensitivity to odors (hyperosmia).
The Covid-19 pandemic has shed light on the role of viral infections in causing olfactory disorders. Infection with the SARS-CoV-2 virus can lead to inflammation and edema that block the upper part of the nasal cavity where the olfactory zone is located. The virus may also directly attack olfactory cells in the nasal epithelium, affecting the function of neurons. Additionally, studies suggest that the virus could infect the olfactory bulb in the brain.
Aside from viral infections, non-infectious conditions like cancer, Alzheimer’s disease, and metabolic disorders can also impact the sense of smell. For instance, 80% of Alzheimer’s patients experience olfactory dysfunction, which can serve as an early indicator of the disease. Recent research has also shown correlations between diabetes, obesity, and olfactory disorders.
Furthermore, emotional factors like stress and aging can influence our sense of smell. Early-life traumas can lead to depression in adulthood, which is often associated with disturbances in odor perception. Aging can also result in presbyosmia, where the ability to perceive pleasant odors diminishes.
Olfactory disorders can have significant implications for daily life, affecting one’s safety, well-being, and social interactions. Individuals with anosmia may face serious accidents or health risks due to the inability to detect dangers in their environment. Additionally, the loss of smell can impact personal relationships and lead to social isolation.
Rehabilitation of the sense of smell through olfactory training has shown promising results, with an estimated recovery rate of 80% in individuals who undergo at least three months of continuous training. This approach involves daily exposure to different odors to stimulate olfactory attention and reconnect the nose to the brain.
In cases where olfactory training is ineffective, alternative treatments such as surgical interventions or medication may be considered. Exciting research is also being conducted on the development of artificial olfactory devices to restore smell perception in anosmic patients.
While these innovative solutions may take time to become widely available, they offer hope for individuals who do not respond to traditional treatments. Ultimately, understanding the complexities of olfactory disorders is crucial for improving the quality of life for those affected by anosmia.