Gustatory Dysfunction and Long COVID in Chinese Patients with COVID-19 Infected with the Omicron Variant: Results from a 6-Month Prospective Follow-Up Study

Background: Gustatory dysfunction is a key syndrome of long COVID in patients with SARS-CoV-2 infection and significantly affects patients' quality of life, however, when and whether the syndrome of gustatory dysfunction persistent in patients is less evaluated. Thus, we prospectively evaluated the incidence, time of onset, recovery time, and associated risk factors of gustatory dysfunction and long COVID-19 in Chinese patients.Methods: We conducted a cross-sectional study including 1304 patients with SARS-CoV-2 Omicron infection at Changxing Mobile Cabin Hospital in Shanghai, China, from March to May 2022. During hospitalization patients’ clinical gustatory dysfunction information was systematically assessed using an electronic questionnaire, covering the incidence and time of onset. A prospective follow-up of 241 patients with gustatory dysfunction was conducted by telephone interviews at 6 months after discharge. The recovery time of gustatory dysfunction was assessed.Findings: Of all 1304 patients, 241 (18.48%) reported gustatory dysfunction, predominantly mild to moderate gustatory dysfunction (87.14%). The median time of onset was 1 day (Q1–Q3, -5–6 days) after presentation of typical COVID-19 symptoms. A history of gustatory dysfunction increased the chance of developing it after COVID-19 infection by 28-fold (OR, 28.803; 95%CI, 11.992 – 69.178; P < 0.001). The 6-month follow-up response rate was 89.63% (216/241) and 94.44% (n=204) of patients reported taste sensation recovery. The median recovery time was 14 (the first quartile–the third quartile, 9–23) days and most patients (74.02%) recovered their taste sense within 1–3 weeks. 20.37% of patients (44/216) presented with long COVID. Having multiple taste impairment (OR, 2.364; 95% CI, 1.286 – 4.348; P = 0.006) and having moderate gustatory dysfunction (OR, 1.978; 95% CI, 1.053 – 3.716; P = 0.034) were associated with a higher risk of gustatory dysfunction with long COVID. Having received a COVID-19 vaccine booster was significantly associated with taste sensation recovery (HR, 1.344; 95% CI, 1.012 – 1.785; P = 0.041) and significantly reduced the recovery time by a mean of 6.232 days (β, -6.232; 95% CI, -11.293 – -1.171; P = 0.016).Interpretation: Nearly one in five patients with COVID-19 might develop long COVID of gustatory dysfunction and 5% with persisting change in their sense of taste. Luckily, most patients recovered taste sensations within 1-3 weeks after COVID-19 symptom onset and receiving a booster shot of the COVID-19 vaccine also presented a protective effect on the recovery of taste sensation. Funding: his work was supported by the Innovative research team of high-level local universities in Shanghai (Grant Number-SHSMU-ZLCX20212401). Declaration of Interest: The authors have no relevant conflicts of interest to declare.Ethical Approval: The present study conforms to principles of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline for observational studies. The protocol was approved by the Ethics Committee of Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (XHEC-C-2022-039-1) and all participants provided informed consent electronically.