UCSF

Objective

Coronavirus disease 2019 (COVID-19) is associated with olfactory dysfunction, but the evolution of the olfactory loss and timeline to recovery are largely unknown. This study examines changes in smell sensitivity in COVID-19-positive (COVID+) and COVID-19-negative (COVID-) viral illness during the initial weeks after infection.

Study design

Cross-sectional cohort comparison.

Setting

National anonymous surveys.

Methods

Survey participants were queried about smell sensitivity and general health status at the time of COVID-19 testing and in the weeks that followed.

Results

In total, 375 (174 COVID+, 201 COVID-) participants completed the survey and 132 (62 COVID+, 70 COVID-) participants completed the 2-week follow-up survey. Normal smell in the COVID+ cohort was less frequent at the time of testing and at follow up (P < .05). Dynamic changes in smell sensitivity in the COVID+ cohort were more frequent in the initial weeks (P < .001). In those with normosmia at the start of infection, 38% of the COVID+ cohort reported worsening smell compared to only 8% in the COVID- cohort (P < .05). Recovery of overall health was associated with normosmia at the time of infection and improvement of smell sensitivity within weeks of infection.

Conclusion

The COVID+ cohort showed greater dynamic change in smell sensitivity and a higher rate of persistent olfactory dysfunction in the weeks after infection. Normal smell at the time of COVID-19 infection may still worsen before recovery. Overall health recovery after viral illness is associated with improvement in smell sensitivity and the absence of initial anosmia or hyposmia.