Efeitos do treinamento olfatório e do ácido alfa-lipoico na perda de olfato pós-COVID-19: um ensaio clínico randomizado

Abstract

Objectives: Olfactory loss is a recognized long-term dysfunction after Coronavirus Disease 2019 (COVID-19) infection. This investigation aimed to assess the effect of alpha-lipoic acid as an adjuvant treatment of olfactory training on the improvement of smell loss in post-COVID-19 patients. Methods: This randomized controlled trial included 128 adult outpatients who had persistent smell loss for more than 3-months after COVID-19 infection. The participants were randomly allocated into two groups: the intervention treatment group, which received alpha-lipoic acid associated to olfactory training, and comparison treatment group, which received placebo pills associated to olfactory training. The participants were followed-up for 12-weeks. Olfactory dysfunction was assessed in terms of Visual Analog Scale (VAS), and the Connecticut Chemosensory Clinical Research Center (CCCRC) test for the Brazilian population.

Results: A total of 100 participants completed the follow-up period and were analyzed in thisstudy. Both groups have improved CCCRC score (p = 0.000), olfactory threshold (p = 0.000), iden-tification score (p = 0.000) and VAS score (p = 0.000) after 12-weeks follow-up. No significantdifferences were determined between the intervention and comparison treatment groups inCCCRC score (p = 0.63), olfactory threshold (p = 0.50), identification score (p = 0.96) and VASscore (p = 0.97). In all these criteria, comparison treatment group went slightly worse. At theendpoint of the study, the frequency of anosmia reduced to 2% in the intervention treatmentgroup and to 7.8% in the comparison treatment group. Also, 16.8% of the intervention group’subjects, and 15.7% of comparison treatment group’s patients reached normosmia.

Conclusions: Overall, there was a strongly significant difference in olfactory function betweenbaseline and endpoint for both groups. However, based on the lack of significant differencebetween the intervention treatment and the comparison treatment groups in terms of olfactorychanges, our study appoints that the alpha-lipoic acid is not better than olfactory training aloneto treat olfactory loss after COVID-19.