Incomplete and Late Recovery of Sudden Olfactory Dysfunction in COVID-19

Introduction: Sudden olfactory dysfunction is a new symptom related to COVID-19, with little data on its duration or recovery rate.

Objective: To characterize patients with sudden olfactory dysfunction during the COVID-19 pandemic, especially their recovery data.

Methods: An online survey was conducted by the Brazilian Society of Otorhinolaryngology and Cervico-Facial Surgery, and Brazilian Academy of Rhinology, including doctors who assessed sudden olfactory dysfunction patients starting after February 1st, 2020. Participants were posteriorly asked by e-mail to verify data on the recovery of sudden olfactory loss and test for COVID-19 at the end of the data collection period.

Results: 253 sudden olfactory dysfunction patients were included, of which 59.1% were females with median age of 36 years, with a median follow-up period of 31 days. 183 patients (72.3%) had been tested for COVID-19, and of those 145 (79.2%) tested positive. Patients that tested positive for COVID-19 more frequently showed non-specific inflammatory symptoms (89.7% vs. 73.7%; p=0.02), a lower rate of total recovery of sudden olfactory dysfunction (52.6% vs. 70.3%; p=0.05) and a longer duration to achieve total recovery (15 days vs. 10 days; p=0.0006) than the ones who tested negative for COVID-19. Considering only positive-COVID-19 patients, individuals with sudden hyposmia completely recovered more often than the ones with sudden anosmia (68.4% vs. 50.0%; p=0.04).

Conclusion: Positive-COVID-19 patients with sudden olfactory dysfunction showed lower total recovery rate and longer duration than negative-COVID-19 patients. Additionally, total recovery was seen more frequently in positive-COVID-19 patients with sudden hyposmia than the ones with sudden anosmia.