Phantosmia May Predict Long-Term Measurable Olfactory Dysfunction After COVID-19.

Objectives: Persistent olfactory dysfunction (OD) after 6 months caused by SARS-CoV-2 infection has been reported with a variable prevalence worldwide. This study aimed to determine the prevalence of long-term OD and identify predisposing factors.

Methods: A prospective cohort study was conducted on 100 adults with COVID-19. Olfactory function was assessed with the University of Pennsylvania Smell Identification Test and a symptom survey at the onset of disease and 30 days later. Patients with persistent quantitative OD at the second assessment were reevaluated after 1 year. Demographic variables, symptoms, and the degree of smell loss were analyzed.

Results: Participants included 100 patients. The mean age was 42.2 ± 15.6 years, 55 (55%) were female, and 56 (56%) were outpatients. Baseline smell loss was identified in 75/100 (75%) patients, decreasing to 39/95 (40%) after 1 month, and persisting in 29 patients after 1 year. Phantosmia at baseline was the only risk factor identified for persistent OD after 1 year (relative risk 2.51; 95% confidence interval 1.53-4.12; p < 0.001). Regardless of the outcome in smell function, a significant decline in olfaction was associated with the presence of phantosmia at 1 month (β = -12.39; 95% CI -19.82 to -4.95; p < 0.01).

Conclusions: SARS-CoV-2 (2019-2020 variants) produced a highly frequent OD that persisted in 29% of the patients after 1 year. The presence of phantosmia at baseline and 1 month was associated with a worse evolution, but phantosmia may interfere with the performance in an identification smell test. A longer follow-up is required in these patients.

Level Of Evidence: 2 Laryngoscope, 132:2445-2452, 2022.