Chemosensory dysfunction often persistent after COVID-19

About half of patients with COVID-19 who experienced loss of smell during the initial illness had not regained their sense of smell 5 months later. Similarly, of patients losing their sense of taste, almost 40% still had not regained it after 5 months.

Chemosensory dysfunction (CD) is a key symptom of COVID-19. About 60% of patients experience alterations in smell and about 50% in taste. Moreover, persistent CD is reported in 20% of patients after viral upper respiratory tract infections [1]. In a cohort of 813 Quebec healthcare workers with a positive COVID-19 diagnosis (mean age 42 years, 84% female), the duration, severity, and trajectory of CD symptoms were evaluated [2]. Subjects were invited to complete a questionnaire on average 5 months after diagnosis, evaluating CD retrospectively during the acute phase, and at the time of questionnaire completion. Results were reported on a scale from 0 to 10 (0: no perception; 10: very strong perception). Additionally, a chemosensory dysfunction home test (CD-HT) was used to objectify olfactory and gustatory symptoms. Results were presented by Dr Nicolas Bussière (University of Quebec, Canada).

Average self-reported olfaction rates were 8.98/10 before the infection, 2.85/10 during the acute phase, and 7.41/10 at the time of answering the questionnaire. Rates for taste were 9.20/10, 3.59/10, and 8.05/10, respectively. Of 580 respondents with a compromised sense of smell during the acute phase, 297 (51.2%) had not regained olfactory functions at the time of completion. Of 527 participants who lost their sense of taste during the initial illness, 200 (38%) had not regained this sense when completing the questionnaire 5 months later. Assessed objectively with the CD-HT, 134 (17%) had persistent loss of smell and 73 subjects (9%) had persistent loss of taste. Dr Bussière mentioned that the possibility of recall bias and variability in CD-HT (product quality, expiration date, brand) are limitations of this study.

In conclusion, persistent CD occurred in approximately 1 out of 5 COVID-19 patients in this study. Reported chemosensory alterations differed between subjective and objective data collection.

1. Hajikhani B, et al. Physiol Rep. 2020;8(18):e14578.
2. Bussière N, et al. Persistent Chemosensory Dysfunction Associated with COVID-19 Infection in a Cohort of Over 700 Health Care Workers. S21.005, AAN 2021 Virtual Congress, 17-22 April.

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Posted on 16 June 2021