A follow-up on quantitative and qualitative olfactory dysfunction and other symptoms in patients recovering from COVID-19 smell loss

Kathrin Ohla, Maria G. Veldhuizen, Tomer Green, Mackenzie E. Hannum, Alyssa J. Bakke, Shima T. Moein, Arnaud Tognetti, Elbrich M. Postma, Robert Pellegrino, Daniel Liang Dar Hwang, Javier Albayay, Sachiko Koyama, Alissa A. Nolden, Thierry Thomas-Danguin, Carla Mucignat-Caretta, Nick S. Menger, Ilja Croijmans, Lina Öztürk, Hüseyin Yanık, Denis PierronVeronica Pereda-Loth, Alexia Nunez-Parra, Aldair M. Martinez Pineda, David Gillespie, Michael C. Farruggia, Cinzia Cecchetto, Marco A. Fornazieri, Carl Philpott, Vera Voznessenskaya, Keiland W. Cooper, Paloma Rohlfs Dominguez, Orietta Calcinoni, Jasper de Groot, Sanne Boesveldt, Surabhi Bhutani, Elisabeth M. Weir, Cara Exten, Paule V. Joseph, Valentina Parma, John E. Hayes, Masha Y. Niv

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Background: Sudden smell loss is a specific early symptom of COVID-19, which, prior to the emergence of Omicron, had estimated prevalence of ~40% to 75%. Chemosensory impairments affect physical and mental health, and dietary behavior. Thus, it is critical to understand the rate and time course of smell recovery. The aim of this cohort study was to characterize smell function and recovery up to 11 months post COVID-19 infection. Methods: This longitudinal survey of individuals suffering COVID-19-related smell loss assessed disease symptoms and gustatory and olfactory function. Participants (n=12,313) who completed an initial survey (S1) about respiratory symptoms, chemosensory function and COVID-19 diagnosis between April and September 2020, were invited to complete a follow-up survey (S2). Between September 2020 and February 2021, 27.5% participants responded (n=3,386), with 1,468 being diagnosed with COVID-19 and suffering co-occurring smell and taste loss at the beginning of their illness. Results: At follow-up (median time since COVID-19 onset ~200 days), ~60% of women and ~48% of men reported less than 80% of their pre-illness smell ability. Taste typically recovered faster than smell, and taste loss rarely persisted if smell recovered. Prevalence of parosmia and phantosmia was ~10% of participants in S1 and increased substantially in S2: ~47% for parosmia and ~25% for phantosmia. Persistent smell impairment was associated with more symptoms overall, suggesting it may be a key marker of long-COVID illness. The ability to smell during COVID-19 was rated slightly lower by those who did not eventually recover their pre-illness ability to smell at S2. Conclusions: While smell ability improves for many individuals who lost it during acute COVID-19, the prevalence of parosmia and phantosmia increases substantially over time. Olfactory dysfunction is associated with broader persistent symptoms of COVID-19, and may last for many months following acute COVID-19. Taste loss in the absence of smell loss is rare. Persistent qualitative smell symptoms are emerging as common long-term sequelae; more research into treatment options is strongly warranted given that even conservative estimates suggest millions of individuals may experience parosmia following COVID-19. Healthcare providers worldwide need to be prepared to treat post COVID-19 secondary effects on physical and mental health. Trial registration: This project was pre-registered at OSF 1.

Original languageEnglish
Pages (from-to)207-217
Number of pages11
Issue number3
Publication statusPublished - 2022


  • long COVID
  • olfaction disorders
  • parosmia
  • phantosmia
  • post-COVID
  • public health
  • smell

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