Olfactory training and nasal microbiota: two paths to recovery from covid-related loss of smell?
Loss of smell is a classic symptom of Covid-19. Particularly troubling for patients, this disorder is also a serious disability. Studies combining daily olfactory training and an analysis of the nasal microbiota are currently under way to help patients regain their sense of smell.
About this article
Loss of smell (anosmia) and taste (ageusia): Covid-19 disturbs our senses. Almost half of symptomatic patients present such disorders1, with strong variations according to ethnicity (e.g. the incidence in Caucasian populations is three times that of Asians)2. Sensory changes are severe in those affected. In a multilingual survey of 4,039 Covid-19 cases worldwide, patients reported an average loss of 80% of their sense of smell and 70% of their sense of taste3.
Daily practice to recover sense of smell
Unfortunately, anosmia is not limited to the often transient cases related to Covid-19. Head trauma, nasal inflammation, allergies and even old age can lead to a loss of smell. The cause? A deterioration in the sensory cells that line the nasal cavities and are responsible for detecting odors. To counteract anosmia, Austrian researchers train their patients to smell and visualize various odors (lemon, rose, etc.) twice a day. The results are positive, with patients regaining their sense of smell after six months of training. Furthermore, MRI imaging shows that the brain areas dedicated to smell are partially restored.
Focus on the nasal microbiota
In addition to this training, the researchers also sought to determine the influence of the microorganisms living in the nasal cavity. They were on the right scent, since they observed a higher diversity of bacteria in the noses of patients with a reduced sense of smell. One bacterium in particular is suspected of altering olfactory performance. Encouraged by these results, the team is taking a close look at whether patient training also modifies the balance of the nasal microbiota. The results are not yet known, but the study raises significant hopes of finding key microbes that are capable of restoring patients’ sense of smell and directing them towards the most appropriate treatment for the disorder.
1. Olfactory dysfunction (43.0%), taste dysfunction (44.6%) and overall chemosensory dysfunction (47.4%).
2. von Bartheld CS, Hagen MM, Butowt R. Prevalence of Chemosensory Dysfunction in COVID-19 Patients: A Systematic Review and Meta-analysis Reveals Significant Ethnic Differences. ACS Chem Neurosci. 2020 Oct 7;11(19):2944-2961. doi: 10.1021/acschemneuro.0c00460.
3. Parma V, Ohla K, Veldhuizen MG et al. More Than Smell—COVID-19 Is Associated With Severe Impairment of Smell, Taste, and Chemesthesis. Chem Senses. 2020 Oct 9;45(7):609-622. doi: 10.1093/chemse/bjaa041.
Scilog. Training can help recover from lost sense of smell. 11 Jan 2021:
Florian Ph. S. Fischmeister: