Olfactory training for olfactory dysfunction in COVID-19: A promising mitigation amidst looming neurocognitive sequelae of the pandemic

Abstract

Olfactory dysfunction (OD) is a recognized symptom of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is independently associated with neurodegenerative disorders. Moreover, the central nervous system manifestations in patients infected with the coronavirus-2019 (COVID-19) have demonstrated cognitive decline and neuropsychiatric manifestations. Hence, OD in COVID-19 necessitates perusal of its mechanism and available treatment options to avert possible development of neurocognitive sequelae of the pandemic. The article presents a literature review organized from the published information about olfactory training (OT) for OD during COVID-19. The methodology comprised retrieval of available literature from database searches and subsequent scrutinization of relevant information. Inferentially, injury to the sustentacular cells, possessing angiotensin-converting enzyme 2 (ACE-2) receptors, is an important mechanism causing OD in COVID-19. Olfactory dysfunction may be prolonged in severe cases of anosmia predisposing to neurodegenerative and cognitive impairment in COVID-19 infection. Olfactory training demonstrates an effective treatment for OD based on human and animal-derived evidence through recent studies. It curtails the progression of OD, besides inducing neural rearrangement and changes in functional connectivity in patients receiving OT. Additionally, contemporary reports support that the administration of OT for COVID-induced anosmia is effective and encompasses no significant adverse effects. The present review highlights the prominence of olfactory training as a recommended intervention for OD in COVID-19. This review can guide the clinicians in curbing neurological repercussions of COVID besides enhancing cognitive rehabilitation through olfactory training.