Persistent Olfactory Dysfunction Caused by COVID-19 Affects Nearly One-Third of Patient Cohort

by Linda Kossoff •

What is the prevalence of long-term olfactory dysfunction (OD) caused by SARS-CoV-2 infection (2019–2020), and what are its predisposing factors?

BOTTOM LINE

COVID-19 produced persistent OD in 29% of cohort at a one-year follow-up evaluation, and phantosmia was associated with persistent OD one year after the disease.

BACKGROUND: OD is a common COVID-19 symptom that usually regresses spontaneously during the first two weeks, but recent evidence indicates that up to 20% of patients have persistent OD at six months after onset. To date, few studies include long-term follow-up of COVID-19 patients using self-reported symptoms and psychophysical testing.

STUDY DESIGN: Prospective cohort study.

SETTING: Otolaryngology Department, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile.

SYNOPSIS: Researchers enrolled 100 adult patients who received a positive COVID-19 diagnosis between April and August 2020. Olfactory function was assessed with the University of Pennsylvania Smell Identification Test (UPSIT) and a symptom survey at the onset of disease and 30 days later. Baseline smell loss was identified in 75% of patients. Thirty-nine patients had OD after 30 days from disease onset. Of these, 29 patients still had OD at the one-year re-evaluation. The presence of phantosmia was associated with a greater risk of persistent OD after one year from symptom onset and a decline in quantitative smell function measured by an identification odor. Authors note that 66% of patients reported normal olfactory function at one year, but the UPSIT score was abnormal at 80.5%, indicating that self-reported OD may be subject to patient bias, emphasizing the need for a psychophysical test to assess abnormal olfactory function. They add that a longer follow-up is required to determine the actual prevalence of persistent OD in COVID-19. Study limitations included the stoppage of follow-up in patients who recovered olfactory function after one month.

CITATION: Leung JS, Cordano VP, Fuentes-López E, et al. Phantosmia may predict long-term measurable olfactory dysfunction after COVID-19. Laryngoscope. 2022;132:2445-2452.