Prevalence and 6-month recovery of olfactory dysfunction: a multicentre study of 1363 COVID-19 patients

Objective: To investigate prevalence and recovery of olfactory dysfunction (OD) in COVID-19 patients according to the disease severity. Methods: From 22 March to 3 June 2020, 2581 COVID-19 patients were identified from 18 European hospitals. Epidemiological and clinical data were extracted at baseline and within the 2-month post-infection. Results: The prevalence of OD was significantly higher in mild form (85.9%) compared with moderate-to-critical forms (4.5–6.9%; P = 0.001). Of the 1916 patients with OD, 1363 completed the evaluations (71.1%). A total of 328 patients (24.1%) did not subjectively recover olfaction 60 days after the onset of the dysfunction. The mean duration of self-reported OD was 21.6 ± 17.9 days. Objective olfactory evaluations identified hyposmia/anosmia in 54.7% and 36.6% of mild and moderate-to-critical forms, respectively (P = 0.001). At 60 days and 6 months, 15.3% and 4.7% of anosmic/hyposmic patients did not objectively recover olfaction, respectively. The higher baseline severity of objective olfactory evaluations was strongly predictive of persistent OD (P < 0.001). Conclusion: OD is more prevalent in mild COVID-19 forms than in moderate-to-critical forms. OD disappeared in 95% of patients regarding objective olfactory evaluations at 6 months.