One-year longitudinal cohort study of chemosensory recovery and plasma biomarker dynamics in SARS-CoV-2 survivors

This study examined the recovery of smell and taste after SARS-CoV-2 viral-clearance and explored biological factors associated with chemosensory outcomes. Participants were enrolled at 3, 6, or 12 months (Group 1, 2 and 3) after viral-clearance (Visit 1) and re-evaluated three months later (Visit 2). Chemosensory functional tests were performed, and biomarkers related to protein aggregation and neurodegeneration, astroglial activation, neuronal injury, and oxidative stress were measured. 120 participants were recruited. In the cohort, gustatory function had largely normalised at the first visit across all groups and remained stable at follow-up. In contrast, significant improvement in olfactory function was observed within 3-6 months post-viral clearance (Group 1), while Groups 2 and 3 exhibited stable olfactory performance at subsequent follow-up assessments. Biomarker α-synuclein is significantly correlated with olfactory performance, however, plasma concentration did not exhibit a significant decline until approximately one-year post-recovery (Group 3), suggesting a delayed biomarker response relative to clinical symptom resolution. These findings suggest that protein aggregation-related processes or underlying susceptibility may be associated with SARS-CoV-2-related olfactory dysfunction. Further long-term mechanistic studies are warranted.