Olfactory dysfunction in patients after recovering from COVID-19

Abstract

Background: Smell and taste disorders occur in COVID-19 with a high prevalence, but little is known about the duration of the symptoms. In particular, studies using validated olfactory tests are very rare to date. Aims/Objectives: The aim of this study was to determine the olfactory function of COVID-19 recoveries by a detailed olfactory test. Methods: 91 patients with PCR-confirmed, past COVID-19 disease were included. Olfactory history was taken using a questionnaire. Olfactory function was evaluated with the sniffin' sticks test, tasting function with taste sprays. Results: 80 patients had experienced sudden olfactory loss during the course of disease and at the time of testing, 33 patients subjectively still had an impaired olfactory sense. Around 8 weeks had passed since the onset of symptoms. 45.1% of the tested individuals were still hyposmic according to the olfactory test while 53.8% showed an olfactory performance within the normal range. Patients' self-assessment correlated poorly with the measured olfactory performance. Conclusions and significance: Half of the patients with an olfactory loss as a symptom of COVID-19 still have olfactory impairments after two months, although not all of these patients subjectively notice a restriction. Long-term measurements must confirm whether all affected patients will make full recovery.

Gaining Back What Is Lost: Recovering the Sense of Smell in Mild to Moderate Patients After COVID-19

“…Our results still showed a portion of participants that remained hyposmic (27%) and similar to the 29% found by Le Bon et al (2020) . A higher percentage of hyposmic was found by Otte et al (2020) after 7 weeks after COVID-19 onset. Discrepancies could be due to several factors such as different study populations, sample size, duration of initial anosmia ( Le Bon et al 2020 ), and days since the onset.…”

Anosmia in the first coronavirus disease 2019 outbreak in Europe: functional recovery after eight months

“…The follow-up period, however, was very short and does not allow us to understand the longterm trend of the symptoms. The need for long-term observational results is supported by Otte et al, 8 who acknowledge that there is currently no literary work evaluating the trend of post-infectious olfactory disorder from SARS-CoV-2 several months after onset. In fact, the same authors followed a series of 80 patients for only two months.…”

“…4 Several studies have since demonstrated the association between anosmia and SARS-CoV-2 infection. [6][7][8][9] We observed an exponential increase of patients with olfactory deficit in the territory of southern Lombardy (the site of the first European Covid-19 outbreak) between the end of February and the beginning of March, and we consequently described the first series in Europe of patients affected by anosmia during SARS-CoV-2 infection. 3 Klapfenstein et al 6 conducted a study on 114 patients affected by Covid-19, in which 54 (47 per cent) were affected by anosmia.…”

“…The continuous succession of studies demonstrating the relationship between anosmia and SARS-CoV-2 infection [10][11][12] has led the World Health Organization (WHO) to consider anosmia as a specific symptom of Covid-19. 8 Once this association was clarified, researchers' efforts were directed towards understanding the pathogenetic mechanisms of anosmia, as described in a paper by Bilinska and Butowt. 13 The long-term evolution of neurological symptomsand of anosmia in particularassociated with Covid-19 remains to be understood.…”

“…13 The long-term evolution of neurological symptomsand of anosmia in particularassociated with Covid-19 remains to be understood. Several studies in the literature illustrate the trend of anosmia in the weeks following the infection, 8,12,14 but very few present long-term follow-up data. We collected data for the population of the first European outbreak and monitored the trend of olfactory disfunction, with an observational period of eight months.…”