High prevalence of long-term olfactory disorders in healthcare workers after COVID-19: A case-control study

  1. Johannes Frasnelli
  2. Arnaud Tognetti
  3. Anja L. Winter
  4. Evelina Thunell
  5. Mats J. Olsson
  6. Nina Greilert
  7. Jonas K. Olofsson
  8. Sebastian Havervall
  9. Charlotte Thålin
  10. Johan N. Lundström

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Abstract

More than a year after recovering from COVID-19, a large proportion of individuals, many of whom work in the healthcare sector, still report olfactory dysfunctions. However, olfactory dysfunction was common already before the COVID-19 pandemic, making it necessary to also consider the existing baseline prevalence of olfactory dysfunction. To establish the adjusted prevalence of COVID-19 related olfactory dysfunction, we assessed smell function in healthcare workers who had contracted COVID‐19 during the first wave of the pandemic using psychophysical testing.

Methods

Participants were continuously tested for SARS‐CoV‐2 IgG antibodies since the beginning of the pandemic. To assess the baseline rate of olfactory dysfunction in the population and to control for the possibility of skewed recruitment of individuals with prior olfactory dysfunction, consistent SARS-CoV‐2 IgG naïve individuals were tested as a control group.

Results

Fifteen months after contracting COVID‐19, 37% of healthcare workers demonstrated a quantitative reduction in their sense of smell, compared to only 20% of the individuals in the control group. Fifty-one percent of COVID‐19‐recovered individuals reported qualitative symptoms, compared to only 5% in the control group. In a follow-up study 2.6 years after COVID-19 diagnosis, 24% of all tested recovered individuals still experienced parosmia.

Conclusions

In summary, 65% of healthcare workers experienced parosmia/hyposmia 15 months after contracting COVID-19. When compared to a control group, the prevalence of olfactory dysfunction in the population increased by 41 percentage points. Parosmia symptoms were still lingering two-and-a half years later in 24% of SARS-CoV-2 infected individuals. Given the amount of time between infection and testing, it is possible that the olfactory problems may not be fully reversible in a plurality of individuals.

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  1. Version published to 10.1371/journal.pone.0306290
  2. Version published to 10.1101/2022.01.20.22269490v3 on medRxiv
  3. Version published to 10.1101/2022.01.20.22269490v2 on medRxiv
  4. ScreenIT

    SciScore for 10.1101/2022.01.20.22269490: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsConsent: Informed consent was obtained, and all aspects approved by the Swedish Ethical Review Authority.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    BlindingParticipants were blindfolded during the threshold and discrimination tests.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    All participants are tested for SARS-CoV-2 IgG antibodies every four months since the start of the pandemic in Sweden3.
    SARS-CoV-2 IgG
    suggested: None

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a protocol registration statement.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  5. Version published to 10.1101/2022.01.20.22269490v1 on medRxiv