Almost 90% of subjects who experience COVID-19-linked taste or smell dysfunction fully recover after two years

By Shanet Susan AlexAug 9 2022Reviewed by Aimee Molineux

In a recent article published in JAMA Otolaryngology Head & Neck Surgery, researchers explored the recovery rate and prevalence of coronavirus disease 2019 (COVID-19)-associated taste and smell impairments after two years across patients with mild symptoms.

Background

Taste and smell dysfunction were some of the often-documented manifestations of mildly symptomatic COVID-19 before the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron strain. Furthermore, 7% of patients had functional anosmia one-year post-SARS-CoV-2 infection, making smell or taste impairment frequent long-lasting COVID-19 symptoms. It is crucial to determine the long-term durability of these symptoms, considering the high COVID-19 case rates.

The present study's authors have previously described the frequency of an altered sense of taste or smell in COVID-19 patients with mild symptoms at initiation, four weeks, eight weeks, and six months after infection.

About the study

In the present work, the researchers analyzed the same group of mildly symptomatic COVID-19 patients they had previously evaluated at onset, four weeks, eight weeks, and six months following SARS-CoV-2 infection to determine the two-year recovery rate and prevalence of taste or smell dysfunction.

The team obtained verbal informed consent from the study participants via telephone interviews. The study volunteers were 18 or older individuals sequentially evaluated at Treviso General Hospital, tested SARS-CoV-2-positive by polymerase chain reaction (PCR) on swab tests conducted following World Health Organization (WHO) recommendations between 19 March and 22 March 2020, and who were deemed fit for home management.

The subjects were evaluated in the acute stage of infection and contacted again after four weeks, eight weeks, six months, and two years. During successive interviews, the volunteers were analyzed using the same inquiries from the baseline. Symptoms were evaluated using structured questionnaires, such as the Sino-nasal Outcome Test 22 and the Acute Respiratory Tract Infection Questionnaire. Symptom prevalence was expressed as a percentage of all participants, and the 95% confidence intervals (CIs) were determined using the Clopper-Pearson technique. In addition, software R, version 3.6, was used to conduct statistical analyses.

Results

The study results indicated that 174, i.e., 86.1%, of the 202 SARS-CoV-2 patients who completed the baseline survey responded to every follow-up interview. Three patients were omitted from the study due to a documented SARS-CoV-2 reinfection, and three were removed due to late-onset, i.e., more than three months, smell or taste dysfunction, indicating possible reinfection. Hence, there were 168, or 83.2%, eligible subjects with a median age of 55, ranging from 20 to 89 years, 90, i.e., 53.6% of whom were women.

Of the eligible study volunteers, 108 or 64.3%, 64 or 38.1%, 29 or 17.3%, 27 or 16.1%, and 14 or 8.3% documented a changed sense of smell or taste with a Sino-nasal Outcome Test 22 score above zero at baseline, four weeks, eight weeks, six months, and two years, respectively. A changed perception of smell or taste was reported initially when the swab screening for SARS-CoV-2 infection was still positive after a four-week follow-up among 11 patients.

Across the 119 patients who experienced smell or taste dysfunction associated with COVID-19 within four weeks, 105 or 88.2% reported complete recovery at two years, 11 or 9.2% reported a decline in severity, and 3 or 2.5% documented the symptom was worse or unchanged. In addition, 13 patients, or 10.9%, experienced a late recovery more than six months following the onset.

At a two-year follow-up, fatigue was the most prevalent non-chemosensory complaint, reported by 31 or 18.5% of participants, succeeded by shortness of breath by 18 or 10.7% of study volunteers. Indeed, 47 patients, or 28%, stated that at least one COVID-19 symptom was still present after two years.

Conclusions

Overall, the study findings showed that over 88% of subjects who experienced COVID-19-linked taste or smell dysfunction fully recovered after two years. Further, about 11% of patients experienced a delayed recovery. 

The current findings require careful interpretation, considering the study's limitations such as outcomes not confirmed for olfactory loss, self-reported data from a cross-sectional survey, lack of a psychophysical assessment of the chemosensory function, small sample size, absence of subjects with severe symptoms, geographical restriction, and lack of information on potential treatments for chemosensory damage. However, unlike the frequent reports, the team mentioned SARS-CoV-2 patients should be informed that recovery of smell or taste impairment may persist for several months from the onset.

Moreover, the study data apply to individuals who contracted the SARS-CoV-2 infection before the emergence of the Omicron variant. Indeed, the chemosensory functions are less commonly and severely affected by COVID-19 associated with the SARS-CoV-2 Omicron strain.