High prevalence of long-term olfactory, gustatory, and chemesthesis dysfunction in post-COVID-19 patients: a matched case-control study with one-year follow-up using a comprehensive psychophysical evaluation.

BACKGROUND

Using an age and gender matched-pair case-control study, we aimed to estimate the long-term prevalence of psychophysical olfactory, gustatory , and chemesthesis impairment at least one year after SARS-CoV-2 infection considering the background of chemosensory dysfunction in non-COVID-19 population.

METHODOLOGY

This case-controlled study included 100 patients who were home-isolated for mildly symptomatic COVID-19 between March and April 2020. One control regularly tested for SARS-CoV-2 infection and always tested negative was matched to each case according to gender and age. Chemosensory function was investigated by a comprehensive psychophysical evaluation including ortho- and retronasal olfaction and an extensive assessment of gustatory function. Differences in chemosensory parameters were evaluated through either Fisher’s exact test or Kruskal-Wallis test.

RESULTS

The psychophysical assessment of chemosensory function took place after a median of 401 days from the first SARS-CoV-2 positive swab. The evaluation of orthonasal smell identified 46% and 10% of cases and controls, respectively, having olfactory dysfunction, with 7% of COVID-19 cases being functionally anosmic. Testing of gustatory function revealed a 27% of cases versus 10% of controls showing a gustatory impairment. Nasal trigeminal sensitivity was significantly lower in cases compared to controls. Persistent chemosensory impairment was associated with emotional distress and depression.

CONCLUSION

More than one year after the onset of COVID-19, cases exhibited an excess of olfactory, gustatory , and chemesthesis disturbances compared to matched-pair controls with these symptoms being associated to emotional distress and depression.