Are essential oils beneficial for patients with COVID-19-related loss of smell? JAMA Study provide insights

In the study, Amish M. Khan and colleagues aimed to examine the efficacy of bimodal visual-olfactory training (OT) and patient-preferred scents versus unimodal olfactory training and physician-assigned odours in COVID-19 olfactory loss.

The researchers did not find any difference between intervention arms based on the changes in the UPSIT (University of Pennsylvania Smell Identification Test) score. Still, they found an association between active intervention and more significant improvement than controls, with a potential benefit of bimodal intervention when exploring within-patient change in UPSIT and self-reported impression of improvement.

There has been a considerable increase in cases of 'loss of smell' because of the COVID-19 pandemic. Therefore, it is essential to identify therapies that aid and accelerate recovery.

The researchers enrolled 275 people aged 18 to 71 years old (mean age 41 years; 86% were female) with current olfactory loss (defined as a UPSIT score of less than 35 for women and less than 34 for men and duration of 3 months or longer) in randomized, single-blinded trial with a 2-by-2 factorial design and an independent control group. The olfactory loss was diagnosed initially within two weeks of the viral infection.

Participants in the physician-assigned odor arms were trained with clove, eucalyptus, lemon, and rose. Patients assigned to the patient-prefered arms chose 4 out of 24 available scents. Participants assigned to the bimodal arm were also shown digital images of the scents (essential oil) they were sniffing. Participants sniffed four essential oils for 15 seconds with a rest of 30 seconds in between odors for three months.

The study led to the following findings:

• The change in UPSIT scores from pre-intervention to post-intervention was comparable between the study arms.
• The marginal mean difference for UPSIT scores change from preintervention to postintervention between people randomized to patient-preferred versus physician-assigned olfactory training was 0.73, and between participants randomized to bimodal versus unimodal olfactory training was 1.10.
• 24% of participants in the control arm had clinically meaningful improvement on UPSIT compared with 53% in the bimodal, patient-preferred arm, for a difference of 29%.
• 19% of participants in the control group self-reported improvement on CGI-I compared with 35% in the bimodal, patient-preferred arm, for a difference of 16%.
• The mean change in ODOR (Olfactory Dysfunction Outcomes Rating) score from preintervention to postintervention was 11.6 points, which was not deemed clinically necessary nor significantly different between arms.

"For patients with olfactory loss, the results failed to show the benefit of olfactory training as measured by UPSIT," the researchers wrote. "Many patients, however, experienced and self-reported clinically significant improvement in olfaction, indicating that patients with COVID-19-related loss of smell may benefit from OT.

"The addition of a visual component to olfactory training may impart potential benefit," they explained. "While natural improvement does occur, the noninvasive nature, low-cost, and minimal OT risk suggests that this treatment should be recommended to patients with postviral olfactory dysfunction (PVOD), as it may give an incremental benefit."

"Future studies should be centred on the identification of population strata for whom olfactory training is probable to be beneficial alone or in combination with other potential treatments," the team concluded.

Reference:

Khan AM, Piccirillo J, Kallogjeri D, Piccirillo JF. Efficacy of Combined Visual-Olfactory Training With Patient-Preferred Scents as Treatment for Patients With COVID-19 Resultant Olfactory Loss: A Randomized Clinical Trial. JAMA Otolaryngol Head Neck Surg. Published online December 29, 2022. doi:10.1001/jamaoto.2022.4112