With the Covid-19 pandemic, it’s right under our noses: diseases can indeed affect our sense of smell. It is possible to lose it suddenly and recover it just as quickly – or not. And the phenomenon has a far-reaching impact on everyday life. The only people who might secretly welcome this unexpected publicity are the “anosmics”, who already suffered from this disorder before the epidemic and often found it impossible to make their voices heard, let alone receive treatment: “There’s nothing we can do” (which is not true), “It may go away by itself” (it does in some cases, but not necessarily), or “It’s not important for humans” (totally false!). And there are many in this situation.
In fact, olfactory dysfunctions, or dysosmias, are quite widespread. It is estimated that between one and five percent of the population in Western countries suffers from anosmia – total loss of smell – while another 20 to 25% experience partial loss, or hyposmia. A survey that we conducted in France between November 2014 and January 2015 tested the olfactory capacities of 3,685 participants of all ages, from every part of the country. Based on scratch-and-sniff cards comprising eight odours, the study allowed us to establish the average dysosmia rate at 17%, and to show that this percentage varies with age, reaching nearly 30% among people over 60.
A study carried out in France in 2014-2015, well before the Covid-19 outbreak, establishes the average dysosmia rate at 17%. This percentage varies with age, reaching nearly 30% among people over 60.
This prevalence has undeniably increased since the emergence of the SARS-CoV-2 virus, for which a loss of the senses of taste and smell was quickly identified as one of the most indicative symptoms. More than 2 million cases of Covid-19 have been documented in France so far, and several studies have estimated that 46 to 86% of sufferers experienced olfactory disorders.12 These symptoms, when they are induced by infections, are known to be of highly variable duration, fleeting for some patients, who recover in a few days, but more lasting or even permanent for others. An experiment conducted by our laboratory has confirmed this variability for Covid-19 patients. In the period between 8 April and 8 May, 2020 alone, at the height of the epidemic, half of the patients reporting olfactory loss had not recovered their sense of smell, in some cases for as long as two months.
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