Human beings only realize the importance of smell and taste when they lose them. And covid-19 has clearly confronted us with this miserable ordeal. Some patients with Covid-19 had dysfunction in their senses (smell and taste) during infection and struggled to recover while others saw this loss continue after recovery.
The covid-19 pandemic has therefore brought smell and taste disorders into the spotlight due to the functional impact and severe distress caused by the loss of these senses, their fundamental diagnostic value, and, more recently, the high rate of long-term dysfunction advances a recent study published in the British Medical Journal (BMJ).
Thus, the meta-analysis carried out by the authors of this work gives a clear picture of the challenge that humans face. Thus, about 5% of people report smell and taste dysfunction six months after covid-19.
And, given that approximately 550 million cases of covid-19 have been reported worldwide as of July 2022, large numbers of patients will seek treatment for these crippling morbidities, the study said, noting that health care systems healthcare must therefore be prepared to provide support to these patients who often report feeling isolated when their symptoms are ignored by clinicians.
« More than the other senses, smell and taste include emotional and affective elements of experience. These meanings cannot be communicated through social media like ideas, imagery and music. Sharing them requires coexistence. The loss of smell and taste affects the quality of life by depriving the people concerned of several daily pleasures and social ties.“, explains the study which specifies that people can also suffer from anorexia, food aversions, malnutrition, anxiety and depression following this loss.
All these disturbances, continues the same source, can be greatly amplified by the appearance of qualitative alterations, in particular by parosmia. This, explains the study, is a fluctuating and distorted olfactory perception, is a common sequela of olfactory dysfunction associated with covid-19, occurring on average three months after infection with SARS-CoV-2.
« For the overwhelming majority, parosmia transforms a pleasant smell into an unpleasant smell, and everyday activities such as smelling coffee and smelling the flavor of food can become disgusting and emotionally distressing.“, supports the study.
Thus, the meta-analysis studies by Tan and colleagues shared in this review were conducted by interviewing patients. Using pen-like odor delivery devices, these psychophysical tests can measure odor thresholds as well as olfactory discrimination and identification abilities.
The same source explains that in a recent case-control study of patients one year after covid-19, it was observed that participants who reported having completely resolved their loss of smell had statistically significant psychophysical olfactory scores lower than those of people with no history of covid-19 matched on sex and age.
« Although an unconscious alteration of the sense of smell does not impact quality of life, it exposes people to potential risks. In addition to eating behavior, nutrition and social communication, smell and taste are crucial for vital functions such as warning of environmental hazards including fires, toxic fumes, gas leaks and spoiled food“, warns the study.
Thus, the study indicates that there is a need to know the pathogenetic mechanisms of SARS-CoV-2-induced olfactory loss, in order to provide us with a stronger basis for the development of new treatment strategies. But the main target for treatment of post-covid-19 anosmia, according to the study, should be the olfactory neuroepithelium.
« Olfactory training, started as soon as possible after symptom onset, is the only disease-specific intervention with evidence of efficacy for the treatment of post-infectious olfactory dysfunction. First proposed by Thomas Hummel in 2009, olfactory training harnesses the unique regenerative abilities of the olfactory neuroepithelium. Patients are advised to sniff and try to identify a sequence of four strong odors – usually rose, eucalyptus, lemon and clove for 15 seconds twice a day for several months“, advocates the study.
In addition to the use of nasal steroids, which aim to resolve SARS-CoV-2-induced inflammation, the study suggests that other treatments which have shown some, albeit marginal, benefit in small clinical trials include intranasal vitamin A and supplements of alpha-lipoic acid and omega-3 fatty acids.
In conclusion, the study believes that health officials, policy makers and research funders should realize the extraordinary importance of good chemo-sensory function for human well-being, allocate adequate resources to support chemo-sensory research and support medical specialists faced with an exceptional number of patients suffering from smell and taste dysfunction.