The long-term effect of COVID-19 infection on olfaction and taste; a prospective analysis

Abstract

Purpose: To estimate long-term prognosis of chemosensory dysfunctions among patients recovering from COVID-19 disease.

Methods: Between April 2020 and July 2022, we conducted a prospective, observational study enrolling 48 patients who experienced smell and/or taste dysfunction during the acute-phase of COVID-19. Patients were evaluated for chemosensory function up to 24 months after disease onset.

Results: During the acute-phase of COVID-19, 80% of patients reported anosmia, 15% hyposmia, 63% ageusia, and 33% hypogeusia. At two years' follow-up, 53% still experienced smell impairment, and 42% suffered from taste impairment. Moreover, 63% of patients who reported parosmia remained with olfactory disturbance. Interestingly, we found a negative correlation between visual analogue scale scores for smell and taste impairments during the acute-phase of COVID-19 and the likelihood of long-term recovery.

Conclusion: Our study sheds light on the natural history and long-term follow-up of chemosensory dysfunction in patients recovering from COVID-19 disease. Most patients who initially suffered from smell and/or taste disturbance did not reach full recovery after 2 years follow-up. The severity of impairment may serve as a prognostic indicator for full recovery.

Keywords: Ageusia; Anosmia; COVID-19; Chemosensory function; Parosmia; Smell.

Fig. 1

Subjective assessment of olfactory function. A Longitudinal changes in the mean VAS for olfactory function. B Initial mean VAS during acute COVID-19, comparing ‘Recovers’ and ‘Non-recovers’ groups, significant differences noted (p < 0.01)

Fig. 2

Subjective assessment of gustatory function. A Longitudinal changes in the mean VAS for gustatory function. B Initial mean VAS during acute COVID-19, comparing ‘Recovers’ and ‘Non-recovers’ groups, significant differences noted (p < 0.01)