Multidimensional benefits of olfactory training for chronic COVID-19-related olfactory dysfunction: a systematic...

Olfactory dysfunction is commonly observed in patients with COVID-19 infection. Chronic olfactory dysfunction can have a profound effect on one’s quality of life. Olfactory training (OT) is a rehabilitation therapy, which has emerged as a viable treatment for COVID-19-related olfactory dysfunction. Our primary objective was to assess the effectiveness of OT for individuals with chronic COVID-19-related olfactory dysfunction.

A search was performed on the Cochrane Library, Embase, PubMed, Scopus, and Web of Science databases from their inception through Feb 24, 2024. Eligible studies included those with sufficient information for meta-analysis pertaining to the effectiveness of OT performed for more than 8 weeks in treating chronic (duration > 16 weeks) COVID-19-related olfactory dysfunction.

After a systematic review of all relevant articles, 9 studies qualified for inclusion. A total of 179 patients within 7 studies had eligible Sniffin' Sticks test data. The pooled results showed significant post-OT increases in TDI score, threshold, discrimination, and identification. Two studies documented qualified UPSIT scores in 63 patients. Pooled results of all identification tests revealed significant improvement.

OT demonstrates benefits in treating chronic COVID-19-related olfactory dysfunction, as evidenced by multidimensional evaluations. These findings suggest the involvement of both top-down and bottom-up mechanisms in the recovery process.