Intensive Olfactory Training in Post-COVID-19 Patients: A Multicenter Randomized Clinical Trial

Abstract

Background Olfactory dysfunction (OD)—including anosmia and hyposmia—is a common symptom of COVID-19. Previous studies have identified olfactory training (OT) as an important treatment for postinfectious OD; however, little is known about its benefits and optimizations after SARS-CoV-2 infection. Objective This study aimed to assess whether olfactory training performance can be optimized using more fragrances over a shorter period of time in patients with persistent OD after COVID-19. In addition, we determined the presence of other variables related to OD and treatment response in this population. Methods This multicenter randomized clinical trial recruited 80 patients with persistent OD and prior COVID-19 infection for less than 3 months. The patients were divided into 2 groups receiving either 4 or 8 essences over 4 weeks. Subjective assessments and the University of Pennsylvania Smell Identification Test (UPSIT) were performed before and after the treatment. Results Significant olfactory improvement was measured subjectively and using the UPSIT in both groups; however, no significant differences between the groups were observed. Additionally, the presence of olfactory fluctuations was associated with higher UPSIT scores. Conclusion These data suggest that training intensification by increasing the number of essences for 4 weeks does not show superiority over the classical method. Moreover, fluctuant olfaction seems to be related to a higher score on the UPSIT.

Use of platelet‐rich plasma for COVID‐19–related olfactory loss: a randomized controlled trial

“…The strongest evidence for the treatment of COVID‐19 OD recommends olfactory training. 7 , 8 , 9 , 10 , 11 Other proposed therapies based on prepandemic evidence involve the use of topical intranasal medications 12 , 13 , 14 and oral anti‐inflammatory/neuroprotective agents. 15 , 16 , 17 , 18 However, the efficacy remains moderate at best among all current proposed therapeutics.…”

“…While a Cochrane review last updated in December 2020 found no definitive treatments for persistent COVID‐19 OD, 6 there are multiple ongoing clinical trials and a few recently published studies. The strongest evidence for the treatment of COVID‐19 OD recommends olfactory training 7–11 . Other proposed therapies based on prepandemic evidence involve the use of topical intranasal medications 12–14 and oral anti‐inflammatory/neuroprotective agents 15–18 .…”

Two-Year Follow-Up on Chemosensory Dysfunction and Adaptive Immune Response after Infection with SARS-CoV-2 in a Cohort of 44 Healthcare Workers

“…Furthermore, olfactory training has been proven to be helpful in postinfectious olfactory loss and can induce neural reorganization processes [ 68 , 69 , 70 , 71 ]. Research on treatment options for chemosensory dysfunction in the context of SARS-CoV-2 is growing [ 19 , 72 , 73 ] and will become more and more important in lessening the impact of long-COVID.…”

Assessing Efficacy Using Variations of Olfactory Training for COVID-19–Related Smell Loss—Would a Rose by Any Other Scent Smell as Strong?

“…This study 1 joins several other recently published studies investigating the use of OT for COVID-19 olfactory dysfunction. [4][5][6] While evidence exists to support OT in non-COVID-19 postviral olfactory loss, 7 its efficacy in COVID-19-related chemosensory dysfunction is less obvious. While 1 study found a clinically meaningful improvement with OT, 4 the results were equivocal in another.…”