Residual olfactory dysfunction in coronavirus disease 2019 patients after long term recovery

Abstract

Introduction Hyposmia is among the most common symptoms of COVID-19 patients. Previous research has mainly described this issue at the disease’s early stages. Because olfactory impairment can indicate neurological degeneration, we investigated the possibility of permanent olfactory damage by assessing hyposmia during the late recovery stage of COVID-19 patients. Methods Ninety-five patients were assessed with the Brief Smell Identification Test for Chinese (B-SITC) and Hyposmia Rating Scale (HRS) after 16 weeks from disease onset. Five weeks later, 41 patients were retested with B-SITC. Results At the first visit, hyposmia was identified in 26/82 (31.7%) and 22/95 (23.2%) of participants by HRS (HRS score ≤22) and B-SITC (B-SITC score <8), respectively. The rates of hyposmia in patients who performed B-SITC after 14–15 weeks, 16–17 weeks, and ≥18 weeks from disease onset were 7/25 (28%), 8/35 (23%) and 7/35 (20%), respectively, which demonstrated a trend of olfaction improvement as recovery time prolonging. Hyposmia percentages decreased from the first visit (34.1%) to the second visit (24.4%) for the 41 patients who completed 2 visits. B-SITC scores of the first-visit hyposmia participants increased significantly at the second visit (5.29 ± 2.02 to 8.29 ± 2.40; n = 14, P = 0.001). Severe cases tended to recover less than common cases. Conclusions Hyposmia was present in up to one-third of COVID-19 patients after about 3 months from disease onset. Notable recovery of olfactory function was observed at a next 5-weeks follow-up. Clinical severity had little influence on olfactory impairment and recovery.

Analysis of Prevalence and Predictive Factors of Long-Lasting Olfactory and Gustatory Dysfunction in COVID-19 Patients

“…The majority of patients (82.6%) showed an altered smell function in the UPSIT test, a considerably higher proportion than the 41.1% found in [ 55 ]. Other groups that quantified the smell through different olfactometry tests, such as the Sniffin’ Sticks test and the Brief Smell Identification test, showed rates for hyposmia from 25.4% to 72.5% [ 23 , 56 ] and 76% [ 57 ], respectively, compared with the 75.3% obtained in our study. The prevalence of anosmia in our study (7.2%) ( Table 9 ) was also higher than rates previously published between 0% and 4% [ 55 , 56 ].…”

“…Another limitation of our study may be due to the appearance or worsening of chemosensory dysfunction caused by other (non-controlled) upper respiratory tract infections during the follow-up period. Although this confusion factor could have led to a selection bias, we should highlight that the protection and isolation measures used for respiratory tract infections during the pandemic helped prevent infections from all respiratory viruses [ 57 , 61 ], and consequently, we can claim that the long-lasting chemosensory impairment seen in our study at the 12-month follow-up may be mostly attributed to the primary SARS-CoV-2 infection.…”

Late neurological consequences of SARS-CoV-2 infection: New challenges for the neurologist

“…Then, SARS-CoV-2 via the olfactory nerve can spread to the olfactory bulb (Desforges et al, 2019 ; Beltrán-Corbellini et al, 2020 ). Clinicians should be alert regarding olfactory disorders which may mark the onset of some neurodegenerative diseases (Zhu et al, 2021 ).…”

Correlation between Post-COVID-19, Chemosensitive Function, Blood Group, and Oral Health-Related Quality of Life

“…In terms of hyposmia, the proportion reported in this work is much higher than that reported in similar studies. About 32% of hyposmia conditions are declared in Chinese patients when assessed objectively three months after hospitalization [ 33 ]. An Israelian study assessed post-COVID-19 hyposmia among 112 patients between 6 weeks to 6 months after symptoms proclaimed 15% smell change [ 34 ].…”