Objective assessment of long-term impact of COVID-19 on multiple sensory functions

This ongoing study investigates the impact of post-acute sequelae of SARS-CoV-2 infection (PASC) on broad sensory functions.

Sixty subjects aged 27-78 years were recruited who had contracted COVID-19 between 1/17/2020 and 12/21/2023 and had persistent symptoms (4.3-52.9, median = 27.48 months). Quantitative sensory assessments included (1) smell: 9-Item NIH toolbox odor identification, detection threshold to phenyl-ethyl alcohol, and retronasal candy test; (2) taste: modified NIH toolbox; (3) chemesthesis: nasal menthol lateralization thresholds and oral capsaicin identification; (4) hearing: pure-tone audiometry, otoacoustic emissions, words-in-noise recognition, and Dichotic Digits Test; (5) vestibular/balance: video head impulse testing, Subjective Visual Vertical, vestibular perceptual thresholds, and modified Romberg balance test; and (6) cognitive assessment: The Self-Administered Gero-Cognitive Exam, Digit Symbol Substitution Test, and Trail-Making Test.

Overall, subjects self-reported high and overlapping dysfunctions: 67.3% smell, 63.6% taste, 56.5% balance and dizziness, 31.8% auditory, and 51.3% brain fog or cognitive dysfunctions, with varying discrepancy to the measured and confirmed deficits (smell 65.5%, taste 16%, vestibular 31.6%, hearing 53.4%, and cognition 19.1%). Significant associations were found between confirmed vestibular and auditory impairments (p = 0.04), and cognitive impairments with central components of vestibular (p = 0.03) and auditory (p = 0.01) impairments, but not with their peripheral components. Similarly, strong associations were found between identification components of smell and taste tests (p = 0.003), which may involve more central processing, but not with threshold tests (a more peripheral process). Hospitalization significantly associated with smell (p = 0.05), cognitive (p = 0.009), vestibular (p = 0. 001), and peripheral auditory (p = 0.01) dysfunctions. Age significantly associated with auditory (p = 0.02), vestibular (p = 0.01) and central olfactory (p = 0.03) dysfunctions.

COVID-19 impacts sensory systems broadly and differently, both peripherally and centrally, driven in part by aging, initial disease severity, and underlying post-COVID cognitive dysfunctions. Subjective symptoms may not always be corroborated by measured deficits.