Therapeutic effects of olfactory training and systemic vitamin A in patients with COVID-19-related olfactory dysfunction: a double-blinded randomized controlled clinical trial

Abstract

Objectives: The new corona virus infection, has a wide range of clinical manifestations. Fever and cough are the most common symptoms. The olfactory function may be also affected with COVID-19. In this randomized clinical trial, we wanted to evaluate the therapeutic effect of olfactory training with and without oral vitamin A for COVID-19-related olfactory dysfunction. Methods: Patients answered to the standard Persian version of anosmia reporting tool and performed the quick smell test before and after 12 weeks and at the end of the 12 months follow up. The patients were randomly allocated to three groups; Group A treatment with olfactory training, Group B treatment with oral vitamin A and olfactory training, and Group C as control group which only underwent nasal irrigation twice a day. Patients were treated for 3 months and followed up for 12 months. Results: Totally 90 patients were included in three groups. After interventions, 76.9% of patients in Group A, 86.7% of patients in Group B, and 26.7% of patients in Group C completely improved. The average intervention time was statistically significant in relationship with the final olfactory status of the patients in the 12 months follow-up. The olfactory training has significantly improved the smell alteration at the end of 3- and 12- months follow-up in A and B groups. Conclusion: A three-months olfactory training is effective for improvement of COVID-19-related olfactory dysfunction. Adding daily oral vitamin A to olfactory training did not lead to better results in improving olfactory dysfunction. Level of evidence: Step 2 (Level 2*): Randomized trial.

Keywords

• COVID-19
• Anosmia
• Olfactory training
• Olfactory impairment
• Vitamin A