Prevalence of smell and taste dysfunction in different clinical severity groups of COVID-19 patients

BACKGROUND: Studies on the long-term prevalence of smell and taste impairment concerned with severe disease in the acute phase of COVID-19 are limited. The aim of our study was to assess and compare psychophysical testing and self-reported smell and taste disturbances and recovery between three patient groups suffering from critical, severe, or mild COVID-19 in a follow-up at six-months after the acute phase. METHODOLOGY: The prospective controlled study of 227 participants comprised 72 intensive-care-unit-treated (ICU-treated), 53 pulmonology- or infectious-diseases-ward-treated (WARD-treated), and 48 home-isolated patients (HOME) with preceding COVID-19, and 54 individuals with no history of COVID-19 (CONTROL). All participants visited a follow-up clinic for a sense-of-smell screening and underwent Magnetic Resonance Imaging (MRI) of the brain, olfactory bulbs and sinonasal area at six months after acute disease. Before the follow-up visit, the participants received a questionnaire concerning smell and taste function. We sent a supplementary questionnaire including questions about phantosmia and parosmia and taste recovery at a median of 502.5 days after the acute phase. RESULTS: We found no statistically significant differences between the groups in the incidence of smell and taste dysfunction, recovery, or the occurrence of parosmia or phantosmia. There were no statistically significant differences in semi-objective smell performance across the different study groups and controls. The olfactory bulb volume was normal in all patients and controls. Mucosal thickening in paranasal sinuses was rare. CONCLUSIONS: We found no difference in a six-month follow-up in the subjective or semi-objective senses of smell and taste between three severity groups of COVID-19 and controls.