Evaluation of long-term results of olfactory training for persistent olfactory dysfunction after COVID-19 infection

Objectives: The study aimed to evaluate the effect of long-term olfactory training (OT) in patients with persistent olfactory dysfunction (OD) following coronavirus disease 2019 (COVID-19) infection. Patients and Methods: The study included patients who developed OD after COVID-19 infection between March 2021 and January 2022. Following the initial examination, olfactory Visual Analog Scale (VAS) scores were recorded before treatment and at 3, 6, and 12 months after treatment. Olfactory training was applied for a period of 12 months to all the patients diagnosed with persistent OD. The procedure was explained in a written document, and four intense smells (phenyl ethyl alcohol [rose], eucalyptol [eucalyptus], citronella [lemon], and eugenol [cloves]) in amber-colored jars were used. The OT scoring was interpreted as follows: 9-10 points, full recovery; 7-8 points, almost full recovery; 5-6 points, semi-recovery; 3-4 points, partial recovery; 1-2 points, no recovery. Kruskal-Wallis one-way analysis of variance was used to compare patients’ VAS scores, with post hoc analysis with Bonferroni correction. Results: Eighty-three patients (57 females, 26 males; mean age: 30.6±11.3 years; range, 17 to 62 years) were included in the analyses. The VAS score of all the patients was 0 before treatment. The mean VAS scores were 6.95±2.3 at three months, 7.59±2.13 at six months, and 7.96±1.97 at 12 months (p=0.0001). Full recovery of OD was obtained with OT in 41 (50%) patients, and one patient showed no recovery. Conclusion: Long-term OT is an effective treatment for persistent OD that developed after COVID-19 infection.