Prevalence of Alpha-Synuclein Seeding Activity in the Olfactory Mucosa following SARS-CoV-2 Infection - Results from a Pilot Study

Prevalence of Alpha-Synuclein Seeding Activity in the Olfactory Mucosa following SARS-CoV-2 Infection - Results from a Pilot Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Prevalence of Alpha-Synuclein Seeding Activity in the Olfactory Mucosa following SARS-CoV-2 Infection - Results from a Pilot Study Werner Poewe, Beatrice Heim, Klaus Seppi, Nicolas De Cleene, Matilde Bongianni, and 9 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8855629/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Olfactory dysfunction (OD) is a hallmark of SARS-CoV-2-infection where it is believed to result from neuroinflammation induced by viral invasion via the olfactory mucosa (OM). Hyposmia also affects the majority of patients with Parkinson’s disease (PD) where it is caused by α-synuclein (aSyn) pathology in the olfactory system, and aSyn-seeding-activity can be detected in the OM using aSyn-seeding-amplification-assays (aSyn-SAA). The present pilot study aimed to investigate whether SARS-CoV-2-infection induces local aSyn-misfolding and -aggregation in OM samples using aSyn-SAA. Methods We conducted an observational study including PD patients (n = 51), individuals with a history of documented symptomatic SARS-CoV-2-infection (post-COVID; n = 98), and healthy controls (HC; n = 42). Post-COVID-participants were stratified based on persistent OD (COVID + OD; n = 44) or normal olfaction (COVID–OD; n = 54) using Sniffin’-Sticks-Identification (SSI) and -Discrimination (SSD) tests. OM samples were obtained by ENT specialists and analyzed by aSyn-SAA at the University of Verona. Clinical phenotyping included MDS-UPDRS, MoCA, and the Innsbruck-RBD-Inventory. Results OM-SAA positivity rates were significantly different between PD and both post-COVID-participants and HCs (80.4% vs 23.4% vs 11.9%; p < 0.001). Within the post-COVID-group, positivity rates were higher in COVID + OD vs COVID–OD (34.1% vs 14.8%; p = 0.038), and COVID + OD differed from HC (p = 0.038), while COVID–OD did not (p = 0.679). Among post-COVID-participants, aSyn-SAA positivity was associated with lower SSI (p = 0.005) and SSD (p = 0.003) scores, but not with MDS-UPDRS, MoCA, or RBD measures. Conclusions OM-SAA-positivity was enriched among individuals with persistent post-COVID-OD and correlated with olfactory impairment. These findings support the hypothesis that neuroinflammation following SARS-COV-2-infection might promote local aSyn-aggregation. The biological and prognostic relevance of OM-SAA positivity is unknown and needs further prospective investigation. Health sciences/Neurology/Neurological disorders/Neurodegenerative diseases/Parkinson's disease Health sciences/Risk factors COVID-19 olfaction olfactory mucosa α-synuclein RT-QuIC Parkinson’s disease hyposmia Introduction Loss of smell is among the most frequent and distinctive symptoms of SARS-CoV-2 infection. Hyposmia is also a characteristic non-motor feature of Parkinson’s Disease (PD) which often precedes the onset of motor symptoms by years or decades, and it has been suggested that α-synuclein (aSyn) pathology in PD may start in the olfactory system and spread via cell-to-cell transmission along interconnected neural circuits. 1 – 7 SARS-CoV-2 may reach the nervous system via olfactory routes, and experimental data indicate that viral neuroinvasion and inflammation can promote aSyn misfolding. 8 – 11 This has raised concerns about a potential of SARS-CoV-2 infections to induce PD and several case reports were published suggesting such a mechanism. 12 Recent studies have reported aSyn seeding activity using seeding amplification assays (SAAs) on olfactory mucosa (OM) samples in subjects with PD and Dementia with Lewy Bodies (DLB) and also in individuals with isolated REM sleep behaviour Disorder (iRBD) who are at risk for either of these diseases. 13 , 14 This pilot study was designed to compare the rates of positive aSyn seeding activity as assessed by SAA in OM samples (OM-SAA) from individuals with a recent history of serologically confirmed COVID-19 and healthy controls without a history of SARS-Cov-2 infection. In addition, a group of patients with clinically established PD were studied as positive controls. We further examined associations between OM-SAA status, olfactory performance, parkinsonian features, cognitive function, and a history of REM sleep behavior disorder (RBD). Methods Study design and participants This observational pilot study included four groups: PD patients (positive control), individuals with prior SARS-CoV-2 infection and a history persistent olfactory dysfunction for ≥ 3 months (COVID + OD), individuals with prior SARS-CoV-2 infection with no or transient (less than three months post infection) olfactory dysfunction (COVID–OD), and healthy controls (HC). For both post-COVID groups, inclusion required documented SARS-CoV-2 infection and an age- and sex-adjusted Sniffin’ Sticks Identification (SSI) score below (OD+ group) or above the 10th percentile (OD- group) at inclusion into this study 15 . General exclusion criteria were pre-existing neurological disorders and any history of subjective hyposmia prior to COVID-19. Participants with COVID + OD were referred from the specialized post-COVID outpatient clinic of our department. Only individuals with Sniffin’ Sticks confirmed persistent OD were invited to participate. COVID–OD and HC participants were recruited through personal contacts and word of mouth among hospital staff and their relatives. Eligibility criteria for HC included age < 75 years, absence of PD symptoms, cognitive impairment, or signs suggestive of RBD, no history of SARS-CoV-2 infection, and no evidence of OD. 15 Patients meeting established clinical diagnostic criteria for PD, 16 were recruited from the movement disorders outpatient clinic and served as a positive control group for the RT-QuIC assay, excluding subjects with dementia or contraindications to olfactory mucosa sampling. All participants provided written informed consent and between April 2021 and January 2024. Clinical assessments All participants underwent a standardized neurological examination, including an assessment of non-motor symptoms of PD, performed by study investigators (BH, KS, NDC, FJ, CC) under the supervision of trained movement-disorder specialists (BH, KS). Motor and non-motor symptoms were assessed using the Movement Disorder Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS, Parts I–III). In addition, cognitive function was screened using the Montreal Cognitive Assessment (MoCA), 17 and the Innsbruck REM Sleep Behavior Disorder Inventory (RBD-I) was used to identify symptoms suggestive of RBD, with a cutoff score of ≥ 0.25 indicating probable RBD. 18 Olfactory function was assessed using the Identification (SSI) and Discrimination (SSD) subtests of Sniffin’ Sticks test battery (Burghart Medizintechnik, Wedel, Germany). To minimize cross-infection risk during the COVID-19 pandemic, odors were presented using a single-use paper sheet to which the tip of the reusable odor pen had been applied, in accordance with the recommendations of the German Society of Otorhinolaryngology, Head and Neck Surgery; consequently, the threshold subtest was omitted because it could not be safely administered under these conditions. 19 Age- and sex-adjusted normative reference values were used, applying the 10th percentile of the Identification subtest as the cut-off for hyposmia screening. 15 OM sampling and RT-QuIC Olfactory mucosa (OM) samples were collected by ENT specialists medial of the middle nasal turbinate in the direction of the superior nasal turbinate using FLOQ-Brushes (Copan Italia). 20 Following the OM collection, swabs were stored at 4°C, and shipped on dry ice to the University of Verona for processing and aSyn-SAA analysis, as previously published. 13 , 14 In particular, recombinant full-length human α-synuclein (aSyn; amino acids 1–140) was prepared in-house. aSyn cDNA was cloned into pET-28a and expressed in E. coli BL21 (DE3). After induction with 0.1 mM IPTG, the periplasmic fraction was isolated, subjected to ammonium sulfate precipitation, and further purified via anion-exchange chromatography (Q-Sepharose, GE Healthcare). Protein purity was verified by SDS-PAGE, and aliquots were dialyzed into 10 mM sodium phosphate buffer (pH 7.4) and stored at − 80°C. For aSyn-SAA, 2 µL of diluted OM homogenate was incubated in 98 µL reaction buffer (100 mM phosphate buffer, pH 8.2; 10 µM Thioflavin T; 0.1 mg/mL recombinant aSyn; 0.004% SDS) containing ~ 37 mg of 0.5 mm glass beads. Reactions were run in triplicate at 30°C in a FLUOstar® Omega plate reader under cycles of shaking (1 min at 200 rpm, double orbital) and rest (14 min), with fluorescence recorded every 45 min (excitation 450 ± 10 nm, emission 480 ± 10 nm). A reaction was considered positive if fluorescence exceeded 10% of the plate’s maximum signal. OM samples were classified as positive if ≥ 2 of 3 replicates crossed this threshold within 50 h, negative if none did, and inconclusive if one of three was positive. Inconclusive samples were reanalyzed and, if results persisted, classified as negative. 14 Statistics All statistical analyses were performed using IBM SPSS Statistics (version 29.0; IBM Corp., Armonk, NY, USA). Age, sex and OM-SAA results were compared among people with PD, individuals with post-COVID-19, and HC. Group comparisons were performed using chi-square tests with Benjamini–Hochberg FDR-corrected post-hoc analyses, and a univariate ANOVA followed by Šidák-corrected post-hoc tests. As the PD cohort was included as a positive control group for the OM-SAA, the PD cohort was not included for further group comparisons. Chi-square tests were applied to assess differences in categorical variables (e.g., sex, persistent hyposmia, OM-SAA positivity) among COVID + OD, COVID-OD, and HC. Group differences in OM-SAA positivity were analyzed using contingency-table statistics. Counts of OM-SAA–positive and –negative individuals were cross-tabulated across three groups (COVID + OD, COVID-OD, and HC). The overall association between group and OM-SAA status was assessed using a two-sided chi-square test of independence (2×3 design), with post-hoc comparisons corrected using the Benjamini–Hochberg FDR procedure; expected cell counts satisfied assumptions for χ² approximation. Effect size was reported as Cramer’s V. To complement these analyses, column-proportion tests with z-statistic annotation were applied for descriptive pairwise comparisons, where groups sharing the same subset label did not differ significantly at p < 0.05. To account for age differences across groups, we conducted a multivariable logistic regression predicting OM-SAA positivity, entering age and sex as covariates. Model significance was assessed using the omnibus χ² statistic, and effects are expressed as odds ratios (95% CI). Additionally, OM-SAA positivity was modelled using multivariable logistic regression for those contrasts identified as significant in the chi-square analysis, with age and sex included as covariates and p-values adjusted via Benjamini–Hochberg FDR correction. Continuous outcomes (e.g., MoCA and MDS-UPDRS scores) were analyzed using analysis of covariance (ANCOVA) models controlling for age and sex, with post-hoc comparisons corrected using the Šidák procedure. Within the post-COVID cohort, differences between participants with and without positive OM-SAA results, were assessed for key demographic and clinical measures. To account for potential confounding by age and sex, analysis of covariance (ANCOVA) models was applied to these continuous outcomes. Demographic and clinical variables were summarized as means ± standard deviations (SD) for continuous measures and as absolute and relative frequencies for categorical variables. Adjusted means from the ANCOVA models are reported with 95% confidence intervals (CI). Due to the lack of existing prevalence data regarding OM-SAA of COVID-19 patients and significant uncertainty regarding their prevalence in HC, a formal power calculation was not conducted. The study was designed as an exploratory pilot to inform future research. The significance threshold was set at p < 0.05 (two-sided, unless stated otherwise). For multiple comparisons, Benjamini–Hochberg FDR correction was applied to chi-square and multivariable logistic regression analyses, and the Šidák procedure was used for ANOVA and ANCOVA, with all p-values referring to the adjusted level unless otherwise stated. Results A total of 191 participants were included: 51 PD patients, 98 post-COVID-19 participants (44 with COVID + OD: n = 44, and COVID–OD: n = 54), and 42 HC. Table 1 summarizes demographic and OM-SAA results for all study groups. OM-SAA was positive in 80.4% of PD, 23.5% of post-COVID, and 11.9% of HC participants (p < 0.001). PD differed significantly from both post-COVID and HC (both p < 0.001), whereas the difference between post-COVID and HC was not significant. Table 1 Demographic and OM-SAA results across study groups. HC (n = 42) COVID-19 (n = 98) PD (n = 51) p-value* Sex (m:f) a 20:22 47:51 32:19 0.190: 0.971/0.216/0.258 Age b 44.83±12.64 49.37±17.95 69.37±9.45 < 0.001: 0.278/<0.001/<0.001 OM-SAA positivity (%) a 5 (11.91) 23 (23.47) 41 (80.39) < 0.001: 0.117/<0.001/<0.001 The significance level is set at p < 0.05. Post-hoc p-values were adjusted using Benjamini–Hochberg FDR correction for chi-square and Šidák correction for ANOVA; all reported p-values are adjusted. * p-value for overall group comparison: HC versus COVID-19/HC versus PD/COVID-19 versus PD. a Chi-square test. b univariate one-way analysis of variance, ANOVA. Clinical and OM-SAA outcomes in the post-COVID-19 cohorts (Table 2 ) Table 2 Demographic and Clinical Variables as well as OM-SAA results in the post-COVID cohorts and healthy controls. HC (n = 42) COVID-OD (n = 54) COVID + OD (n = 44) p-value* Sex (m:f) a 20:22 25:29 22:22 0.935: 0.897 /0.897 /0.897 Age b 44.83±12.64 43.30±16.58 56.82±16.87 < 0.001: 0.951/ 0.002/ <0.001 Months since COVID-19 c NA 16.89±10.54 17.39±9.21 0.806 OM-SAA positivity (%) a 5 (11.9) 8 (14.8.5) 15 (34.1) 0.018: 0.679/0.038/0.038 mean±SD mean adj (96%CI) mean±SD mean adj (96%CI) mean±SD mean adj (96%CI) SSI d 14.76±1.03 14.65 (14.27–15.02) 14.80±1.14 14.62 (14.29–14.95) 8.48±1.78 8.38 (8.42–9.19) < 0.001: 0.999/ <0.001/ <0.001 SSD d 14.83±1.19 14.72 (14.12–15.33) 13.83±2.04 13.67 (13.14–14.21) 10.32±2.55 10.62 (10.00-11.23) < 0.001: 0.030/ <0.001/ <0.001 MoCA d 29.33±0.90 29.17 (28.77–29.57) 28.88±1.55 28.65 (28.29-29.00) 27.93±1.90 28.38 (27.98–28.78) 0.021: 0.142/ 0.022/ 0.710 MDS-UPDRS I d 0.50±1.07 0.71 (-0.35-1.77) 1.70±3.28 2.02 (1.08–2.96) 3.55±5.13 2.96 (1.88–4.03) 0.060: 0.188/ 0.013/ 0.509 MDS-UPDRS II d 0.00±0.00 0.12 (-0.50-0.73) 0.35±1.78 0.52 (-0.03-1.07) 1.25±3.12 0.93 (0.30–1.56) 0.199: 0.697/ 0.204/ 0.719 MDS-UPDRS III d 0.60±1.56 0.95 (-0.33-2.22) 1.15±3.08 1.66 (0.52–2.78) 4.09±7.19 3.13 (1.83–4.43) 0.066: 0.797/ 0.064/ 0.279 MDS-UPDRS total d 1.02±1.96 1.70 (-0.88-4.28) 3.20±7.11 4.19 (1.89–6.49) 8.89±13.85 7.03 (4.40–9.65) 0.021: 0.391/ 0.017 0.320 RBD-I score d 0.10±0.29 0.13 (-0.09-0.34) 0.19±0.55 0.23 (0.04–0.42) 0.45±1.09 0.37 (0.15–0.59) 0.598: 0.851/ 0.735/ 0.328 The significance level is set at p < 0.05. Post-hoc p-values were adjusted using Benjamini–Hochberg FDR correction for chi-square and logistic regression analyses and Šidák correction for ANOVA/ANCOVA; all reported p-values are adjusted. * p-value for overall group comparison: HC versus COVID-OD/HC versus COVID + OD/COVID-OD versus COVID + OD. a Chi-square test. b univariate one-way analysis of variance, ANOVA. c independent two-sample t-test. d univariate analysis of covariance (ANCOVA) corrected for age and sex (mean adj , adjusted mean derived from univariate ANCOVA with age and sex as covariates). Table 2 summarizes demographic, clinical and olfactory data as well as OM-SAA results between HC and the post-COVID-19 groups. Across the 140 individuals from the HC and post-COVID-19 cohorts, OM-SAA positivity was detected in 20.0% of cases (28/140). OM-SAA positivity rates differed across groups, with 11.9% in HC, 34.1% in COVID + OD, and 14.8% in COVID-OD. A chi-square test of independence confirmed a significant overall association between diagnostic group and OM-SAA status (χ²(2) = 8.09, p = 0.018), corresponding to a small-to-medium effect (Cramer’s V = 0.24). OM-SAA positivity was significantly higher in COVID + OD compared with both, HC and COVID-OD (both p = 0.038), while no difference was observed in COVID-OD relative to HC. After applying Benjamini–Hochberg FDR adjustment, only contrasts involving COVID + OD remained significant. Post-hoc z-based column-proportion tests reproduced this pattern, indicating higher positivity exclusively in COVID + OD, while HC and COVID-OD did not differ. Moreover, when comparing COVID + OD participants with COVID − OD participants and HC, olfactory dysfunction remained significantly associated with OM-SAA positivity after adjustment for age and sex (omnibus χ²(4) = 9.91, p = 0.042, R²=0.108). Group allocation was the only significant predictor in the overall model, with higher odds of OM-SAA positivity in COVID + OD relative to HC (OR = 3.84, 95% CI 1.17–12.57, β = 1.35, SE = 0.61, p = 0.026) and COVID + OD (OR = 2.95, 95% CI 1.02–8.52, β = 1.08, SE = 0.54, p = 0.046), whereas age and sex showed no effects. Additionally, OD remained significantly associated with OM-SAA positivity after adjustment for age and sex when comparing COVID + OD with HC (OR = 3.58, 95% CI 1.05–12.25; β = 1.25, SE = 0.63) and when comparing COVID + OD with COVID–OD participants (OR = 3.07, 95% CI 1.03–9.12; β = 1.12, SE = 0.56), with both comparisons yielding p = 0.044. These results are consistent with the categorical analyses, indicating that OM-SAA positivity is selectively elevated in the COVID + OD group. To test whether there were group differences in the continuous clinical variables between healthy controls and post-COVID groups, we conducted univariate ANCOVAs with age and sex as covariates. After adjustment, MoCA scores differed significantly between groups (F = 3.97, p = 0.021, partial η²=0.056; overall model fit: R²=0.376, adjusted R²=0.357). Age showed a strong association with MoCA performance (F = 49.78, p < 0.001, partial η²=0.269), whereas sex did not (F = 2.31, p = 0.131). Post-hoc comparisons indicated that this effect was driven by lower MoCA scores in the COVID + OD compared to the HC group (p = 0.022). Similarly, after adjustment, there was a significant association of MDS-UPDRS-total scores (F = 3.95, p = 0.021, partial η²=0.055; overall model fit: R²=0.241; adj. R²=0.218) with groups. Age was strongly associated with MDS-UPDRS-total scores (F = 21.78, p < 0.001, partial η²=0.139), whereas sex was not (F = 1.38, p = 0.242). Post-hoc comparisons indicated that this effect was driven by higher MDS-UPDRS-total scores in the COVID + OD relative to the healthy control group (p = 0.017). This was driven by higher MDS-UPDRS I scores in the COVID + OD cohort (F = 4.29, p = 0.016, partial η²=0.060; see Table 2 ), while MDS-UPDRS-II (F = 1.63, p = 0.199) and -III (F = 2.78, p = 0.066) did not differ between groups. Olfactory and Clinical Outcomes by OM-SAA Positivity (Table 3) Table 3 Post-COVID Participants With vs. Without Positive OM SAA Activity. aSyn-SAA negative (n = 75) aSyn-SAA positive (n = 23) p-value Sex (m:f) a 32:43 15:8 0.058 age b 48.33±17.78 52.74±18.47 0.306 mean±SD mean adj (96%CI) mean±SD mean adj (96%CI) SSI c 12.53±3.20 12.42 (11.77–13.09) 10.09±3.74 10.43 (9.23–11.64) 0.005 SSD c 12.73±2.56 12.68 (12.12–13.24) 10.70±3.30 10.87 (9.84–11.90) 0.003 MDS-UPDRS I c 2.31±4.41 2.40 (1.46–3.34) 3.26±3.88 2.95 (1.24–4.67) 0.580 MDS-UPDRS II c 0.84±2.81 0.87 (0.33–1.42) 0.48±1.04 0.37 (-0.63-1.37) 0.388 MDS-UPDRS III c 2.55±6.13 2.58 (1.46–3.70) 2.22±2.61 2.12 (0.07–4.17 0.700 MDS-UPDRS total c 5.69±12.19 5.85 (3.55–8.15) 5.96±5.69 5.44 (1.25–9.64) 0.867 MoCA c 28.63±1.65 28.55 (28.22–28.87) 27.91±2.07 28.18 (27.58–28.78) 0.292 RBD score c 0.24±0.73 0.26 (0.07–0.45) 0.52±0.84 0.47 (0.12–0.81) 0.294 The significance level is set at p < 0.05. a Chi-square test. b univariate one-way analysis of variance, ANOVA. c univariate analysis of covariance (ANCOVA) corrected for age and sex (mean adj , adjusted mean derived from univariate ANCOVA with age and sex as covariates). Abbreviations: aSyn, alpha-synuclein; COVID-OD, post-covid cohort without persistent olfactory dysfunction; COVID + OD, post-COVID cohort with persistent olfactory dysfunction; HC, healthy controls; MDS-UPDRS, Movement Disorders Unified Disease Parkinson’s Rating Scale; MoCA, Montreal Cognitive Assessment; n, number; OM-SAA, olfactory mucosa seeding amplification assay; RBD-I, Innsbruck RBD Inventory; SD, standard deviation; SSD, Sniffin’ Sticks Discrimination test; SSI, Sniffin’ Sticks Identification test. To test whether OM-SAA positivity was associated with olfactory function, we conducted a univariate ANCOVA with age and sex as covariates. After adjustment, OM-SAA positive participants showed significantly lower Sniffin’ Sticks Identification scores than OM-SAA negative individuals (F = 8.18, p = 0.005, partial η²=0.080; overall model fit: R²=0.345, adjusted R²=0.324). Age was strongly associated with Sniffin’ Sticks Identification performance (F = 35.92, p < 0.001, partial η²=0.276), whereas sex was not (F = 0.03, p = 0.874). For Sniffin’ Sticks discrimination, OM-SAA positive individuals likewise showed significantly lower scores than OM-SAA negative participants (F = 9.23, p = 0.003, partial η²=0.089; overall model fit: R²=0.296; adjusted R²=0.274). Age was again a strong predictor of performance (F = 27.27, p < 0.001, partial η²=0.225), whereas sex showed no significant association (F = 0.69, p = 0.409). As summarized in Table 3 , no significant associations were observed between OM-SAA positivity and MDS-UPDRS total or subscores, MoCA, or RBD-I scores. Discussion In this pilot study OM aSyn seeding activity was detected in approximately one-third of individuals with persistent OD after COVID-19, while OM-SAA positivity rates in post-COVID participants without OD were similar to HC (14.8% vs 11.9%) and thus overall consistent with previous studies. 13 , 14 As expected, OM-SAA positivity rate was high in participants with PD (80.4%) and well within the upper range of previously reported studies using the OM matrix. 14 Although overall OM-SAA positivity did not differ significantly between the entire post-COVID cohort and HC, the higher rate among participants with persistent OD suggests that SARS-CoV-2–related injury to the olfactory mucosa may trigger local aSyn misfolding in the context of inflammation. Whether such peripheral aSyn aggregation can persist and propagate centrally and eventually cause clinically manifest PD or other synucleinopathy remains speculative. Moreover, COVID + OD participants showed lower MoCA and higher MDS-UPDRS total scores, with the latter being most plausibly driven by increased MDS-UPDRS-I scores. While causality cannot be inferred from the present data, this pattern may be compatible with reports suggesting that persistent post-COVID OD can co-occur with broader neuropsychiatric sequelae — including fatigue, affective symptoms, sleep disturbances, and cognitive impairment. 21 , 22 , 23 , 24 , 25 Experimental studies have shown detrimental effects of SARS-CoV-2 on substantia nigra dopaminergic neurons as well as stem cell derived dopaminergic neurons, 26–28 and SARS-CoV-2 induced neuroinflammation has been suggested to trigger aSyn misfolding and aggregation with a potential to aggravate or induce a-synucleinopathies. 29 , 30 , 31 Although the observation of increased rates of OM-SAA positivity in post-COVID-19 subjects with persistent OD seems biologically plausible given SARS-CoV-2 olfactory tropism and the pro-aggregatory potential of neuroinflammation, 8,10,11 the present results are insufficient to conclude on the prognostic relevance of this finding. Longterm follow-up will be needed to shed light on this evidence and to determine whether post-infectious OM-SAA positivity represents a transient observation or a persistent finding. While the assessment of OM-SAA positivity in individuals with a history of SARS-CoV-2 infection together with objective olfactory and clinical phenotyping are strengths of this study; it is still limited by the small sample size of post-COVID subjects, the difficulty of recruiting COVID-naïve HC due to the increasing prevalence of SARS-CoV-2 exposure and previous infections in the general population over time, and the cross-sectional design. Furthermore, we cannot fully exclude that some HC may have had an unrecognized (‘silent’) prior SARS-CoV-2 infection, since nucleocapsid antibody testing—which would allow discrimination between infection- and vaccination-induced seroreactivity—was introduced at our institution only after HC recruitment had been completed. Conclusions OM-SAA positivity was enriched among individuals with persistent post-COVID OD and correlated with olfactory impairment. Whether this finding reflects a transient post-infectious phenomenon or an early synucleinopathy signature remains to be determine. Abbreviations COVID-OD post-covid cohort without persistent olfactory dysfunction COVID + OD post-COVID cohort with persistent olfactory dysfunction HC healthy controls MDS-UPDRS Movement Disorders Unified Disease Parkinson’s Rating Scale MoCA Montreal Cognitive Assessment n number OM-SAA olfactory mucosa seeding amplification assay RBD-I Innsbruck RBD Inventory SD standard deviation SSD Sniffin’ Sticks Discrimination test SSI Sniffin’ Sticks Identification test. Declarations Funding Austrian Science Fund (FWF) Clinical Research project KLI 1037-B . Author contributions WP conceived the study, initiated the research idea, and substantially contributed to the conceptual design in early discussions with collaborators. BH directed the study, coordinated its implementation, and supervised data collection. KS made major contributions to the research idea, contributed to study design, clinical oversight, and patient phenotyping. JS and TG performed the ENT procedures and OM sampling. MB, EB, and GZ conducted and supervised the RT-QuIC analyses in Verona. BH, NDC, KS, and CC managed, curated, and organized the clinical and laboratory data. BH, KS, NDC, FJ, PK, and JLR contributed to clinical assessments, recruitment, and data acquisition. GW provided infectious-disease expertise and oversight during recruitment and clinical characterization. Acknowledgments The authors are grateful to all participants for their personal commitment to make this study possible Data availability All de-identified data supporting the findings of this study will be made openly available in a public data repository upon publication. A persistent link and DOI will be provided in the final version of the manuscript. 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CNS Neurosci Ther 26:499–501. 10.1111/cns.13372 Epub 2020 Apr 7 Brundin P, Nath A, Beckham JD, Is (2020) COVID-19 a Perfect Storm for Parkinson's Disease? Trends Neurosci 43:931–933. 10.1016/j.tins.2020.10.009 Epub 2020 Oct 21 Stefani A, Iranzo A, Holzknecht E et al Alpha-synuclein seeds in olfactory mucosa of patients with isolated REM sleep behaviour disorder. Brain 144, 1118–1126 (2921). 10.1093/brain/awab005 Bongianni M, Catalan M, Perra D et al (2022) Olfactory swab sampling optimization for α-synuclein aggregate detection in patients with Parkinson's disease. Transl Neurodegener 37. 10.1186/s40035-022-00311-3 Oleszkiewicz A, Schriever VA, Croy I, Hähner A, Hummel T (2019) Updated Sniffin' Sticks normative data based on an extended sample of 9139 subjects. Eur Arch Otorhinolaryngol 276:719–728. 10.1007/s00405-018-5248-1 Epub 2018 Dec 15 Postuma RB, Berg D, Stern M et al (2015) MDS clinical diagnostic criteria for Parkinson's disease. Mov Disord 30:1591–1601. 10.1002/mds.26424 Nasreddine ZS, Phillips NA, Bédirian V et al (2005) The Montreal Cognitive Assessment, MoCA: a brief screening tool for mild cognitive impairment. J Am Geriatr Soc 53:695–699. 10.1111/j.1532-5415.2005.53221.x Frauscher B, Ehrmann L, Zamarian L et al (2012) Validation of the Innsbruck REM sleep behavior disorder inventory. Mov Disord 27:1673–1678. 10.1002/mds.25223 https:// smelltest.eu/wp-content/uploads/2020/04/Handlungsempfehlungen_HNO-Elektiveingriffe_Corona_28-4-20.pdf Bongianni M, Orrù C, Groveman BR et al (2017) Diagnosis of Human Prion Disease Using Real-Time Quaking-Induced Conversion Testing of Olfactory Mucosa and Cerebrospinal Fluid Samples. JAMA Neurol 74:155–162. 10.1001/jamaneurol.2016.4614 Paranhos ACM, Dias ARN, Mendes EAR et al (2025) Persistent olfactory dysfunction as an indicator of cognitive impairment in long COVID-19 syndrome: implications for monitoring and rehabilitation. Eur Arch Psychiatry Clin Neurosci Epub ahead print. 10.1007/s00406-025-02116-7 Vilarello BJ, Jacobson PT, Tervo JP et al (2023) Olfaction and neurocognition after COVID-19: a scoping review. Front Neurosci 17:1198267. 10.3389/fnins.2023.1198267 Alqahtani AS, Aldhahi MI, Alqahtani F, Altamimi M, Alshehri MM (2022) Impact of the loss of smell on the sleep quality and fatigue level in COVID–19 survivors. Eur Arch Otorhinolaryngol 279:4443–4449. 10.1007/s00405-022-07381-z Yoo JH, Kim TS, Kim JS, Lee SH, Seo MY (2025) Subjective distress mediates the association between olfactory dysfunction duration and depression in post COVID 19 patients. Sci Rep 15:22216. 10.1038/s41598-025-07953-z Saak TM, Tervo JP, Vilarello BJ, Jacobson PT et al (2024) Depression, Anxiety, and Neuropsychiatric Symptom Burden in a Longitudinal Cohort with Persistent Psychophysical Post-COVID Olfactory Dysfunction. Brain Sci 14:1277. 10.3390/brainsci14121277 Pokharel BR, Majumdar N, Williams F et al (2025) SARS-CoV-2 infection of substantia nigra pars compacta induces expression of miR-330-5p at 10 days post-infection. J Gen Virol 106:002149. 10.1099/jgv.0.002149 Yang L, Kim TW, Han Y et al (2024) SARS-CoV-2 infection causes dopaminergic neuron senescence. Cell Stem Cell 31:196–211e6. 10.1016/j.stem.2023.12.012 Lee B, Choi HN, Che YH et al (2024) SARS-CoV-2 infection exacerbates the cellular pathology of Parkinson's disease in human dopaminergic neurons and a mouse model. Cell Rep Med 5:101570. 10.1016/j.xcrm.2024.101570 Motyl JA, Gromadzka G, Czapski GA, Adamczyk A (2024) SARS-CoV-2 Infection and Alpha-Synucleinopathies: Potential Links and Underlying Mechanisms. Int J Mol Sci 25:12079. 10.3390/ijms252212079 Boura I, Qamar MA, Daddoveri F et al (2023) SARS-CoV-2 and Parkinson's Disease: A Review of Where We Are Now. Biomedicines 11:2524. 10.3390/biomedicines11092524 Li H, Qian J, Wang Y et al (2024) Potential convergence of olfactory dysfunction in Parkinson's disease and COVID-19: The role of neuroinflammation. Ageing Res Rev 97:102288. 10.1016/j.arr.2024.102288 Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8855629","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":590996115,"identity":"0d60df28-b22b-4bb8-a80a-fb6d0462af2d","order_by":0,"name":"Werner 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Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Beatrice","middleName":"","lastName":"Heim","suffix":""},{"id":590996117,"identity":"80ed9e5b-f926-4177-ab30-acef628c04ce","order_by":2,"name":"Klaus Seppi","email":"","orcid":"","institution":"Innsbruck Medical University","correspondingAuthor":false,"prefix":"","firstName":"Klaus","middleName":"","lastName":"Seppi","suffix":""},{"id":590996118,"identity":"4284ea2b-91ea-4c65-8c9f-4d878bd67663","order_by":3,"name":"Nicolas De Cleene","email":"","orcid":"","institution":"Medical University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Nicolas","middleName":"","lastName":"De Cleene","suffix":""},{"id":590996119,"identity":"bfed4a94-7684-4f39-80c7-b5479e1a0713","order_by":4,"name":"Matilde Bongianni","email":"","orcid":"","institution":"University of Verona","correspondingAuthor":false,"prefix":"","firstName":"Matilde","middleName":"","lastName":"Bongianni","suffix":""},{"id":590996120,"identity":"10e61745-6da6-4ffb-8af1-49d91310f66f","order_by":5,"name":"Erika Bronzato","email":"","orcid":"","institution":"University of Verona","correspondingAuthor":false,"prefix":"","firstName":"Erika","middleName":"","lastName":"Bronzato","suffix":""},{"id":590996121,"identity":"15bf6972-8d2d-4128-9306-8e7c2f1c1703","order_by":6,"name":"Clancy Cerejo","email":"","orcid":"","institution":"Medical Universtiy of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Clancy","middleName":"","lastName":"Cerejo","suffix":""},{"id":590996122,"identity":"bcf14102-df39-4ba7-aae7-8278f36127ae","order_by":7,"name":"Frank Jagusch","email":"","orcid":"","institution":"Medical University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Frank","middleName":"","lastName":"Jagusch","suffix":""},{"id":590996123,"identity":"6fbdda45-0d9f-4883-9082-46d87479eead","order_by":8,"name":"Philipp Kindl","email":"","orcid":"","institution":"Medical University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Philipp","middleName":"","lastName":"Kindl","suffix":""},{"id":590996124,"identity":"a3e0e432-970a-4c73-b670-e0909db2051a","order_by":9,"name":"Judith Löffler-Ragg","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Judith","middleName":"","lastName":"Löffler-Ragg","suffix":""},{"id":590996125,"identity":"ab44086f-6858-41fd-8c79-e8b811bc5340","order_by":10,"name":"Günter Weiss","email":"","orcid":"https://orcid.org/0000-0003-0709-2158","institution":"Department of Internal Medicine II, Medical University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Günter","middleName":"","lastName":"Weiss","suffix":""},{"id":590996126,"identity":"34eac321-27d4-4e56-8e14-7e7f0a520876","order_by":11,"name":"Timo Gottfried","email":"","orcid":"","institution":"Medical University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Timo","middleName":"","lastName":"Gottfried","suffix":""},{"id":590996127,"identity":"0a8ad927-9ecc-4b69-b0e3-f935b5f5d381","order_by":12,"name":"Joachim Schmutzhard","email":"","orcid":"","institution":"Medical University of Innsbruck","correspondingAuthor":false,"prefix":"","firstName":"Joachim","middleName":"","lastName":"Schmutzhard","suffix":""},{"id":590996128,"identity":"419c6fce-7845-401d-8bbb-717b20e19bc4","order_by":13,"name":"Gianluigi Zanusso","email":"","orcid":"","institution":"University of Verona","correspondingAuthor":false,"prefix":"","firstName":"Gianluigi","middleName":"","lastName":"Zanusso","suffix":""}],"badges":[],"createdAt":"2026-02-11 21:15:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8855629/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8855629/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107707271,"identity":"5f09fff4-dd80-4822-85fc-f89c05329003","added_by":"auto","created_at":"2026-04-24 09:19:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":356737,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8855629/v1/b2a8dab2-74bd-4b1c-ba19-1e2ec92715a7.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Prevalence of Alpha-Synuclein Seeding Activity in the Olfactory Mucosa following SARS-CoV-2 Infection - Results from a Pilot Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLoss of smell is among the most frequent and distinctive symptoms of SARS-CoV-2 infection. Hyposmia is also a characteristic non-motor feature of Parkinson\u0026rsquo;s Disease (PD) which often precedes the onset of motor symptoms by years or decades, and it has been suggested that α-synuclein (aSyn) pathology in PD may start in the olfactory system and spread via cell-to-cell transmission along interconnected neural circuits.\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3 CR4 CR5 CR6\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eSARS-CoV-2 may reach the nervous system via olfactory routes, and experimental data indicate that viral neuroinvasion and inflammation can promote aSyn misfolding.\u003csup\u003e\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e This has raised concerns about a potential of SARS-CoV-2 infections to induce PD and several case reports were published suggesting such a mechanism.\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eRecent studies have reported aSyn seeding activity using seeding amplification assays (SAAs) on olfactory mucosa (OM) samples in subjects with PD and Dementia with Lewy Bodies (DLB) and also in individuals with isolated REM sleep behaviour Disorder (iRBD) who are at risk for either of these diseases.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e This pilot study was designed to compare the rates of positive aSyn seeding activity as assessed by SAA in OM samples (OM-SAA) from individuals with a recent history of serologically confirmed COVID-19 and healthy controls without a history of SARS-Cov-2 infection. In addition, a group of patients with clinically established PD were studied as positive controls. We further examined associations between OM-SAA status, olfactory performance, parkinsonian features, cognitive function, and a history of REM sleep behavior disorder (RBD).\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and participants\u003c/h2\u003e \u003cp\u003eThis observational pilot study included four groups: PD patients (positive control), individuals with prior SARS-CoV-2 infection and a history persistent olfactory dysfunction for \u0026ge;\u0026thinsp;3 months (COVID\u0026thinsp;+\u0026thinsp;OD), individuals with prior SARS-CoV-2 infection with no or transient (less than three months post infection) olfactory dysfunction (COVID\u0026ndash;OD), and healthy controls (HC). For both post-COVID groups, inclusion required documented SARS-CoV-2 infection and an age- and sex-adjusted Sniffin\u0026rsquo; Sticks Identification (SSI) score below (OD+ group) or above the 10th percentile (OD- group) at inclusion into this study\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. General exclusion criteria were pre-existing neurological disorders and any history of subjective hyposmia prior to COVID-19.\u003c/p\u003e \u003cp\u003eParticipants with COVID\u0026thinsp;+\u0026thinsp;OD were referred from the specialized post-COVID outpatient clinic of our department. Only individuals with Sniffin\u0026rsquo; Sticks confirmed persistent OD were invited to participate. COVID\u0026ndash;OD and HC participants were recruited through personal contacts and word of mouth among hospital staff and their relatives.\u003c/p\u003e \u003cp\u003eEligibility criteria for HC included age\u0026thinsp;\u0026lt;\u0026thinsp;75 years, absence of PD symptoms, cognitive impairment, or signs suggestive of RBD, no history of SARS-CoV-2 infection, and no evidence of OD.\u003csup\u003e15\u003c/sup\u003e\u003c/p\u003e \u003cp\u003ePatients meeting established clinical diagnostic criteria for PD,\u003csup\u003e16\u003c/sup\u003e were recruited from the movement disorders outpatient clinic and served as a positive control group for the RT-QuIC assay, excluding subjects with dementia or contraindications to olfactory mucosa sampling.\u003c/p\u003e \u003cp\u003e All participants provided written informed consent and between April 2021 and January 2024.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eClinical assessments\u003c/h3\u003e\n\u003cp\u003eAll participants underwent a standardized neurological examination, including an assessment of non-motor symptoms of PD, performed by study investigators (BH, KS, NDC, FJ, CC) under the supervision of trained movement-disorder specialists (BH, KS). Motor and non-motor symptoms were assessed using the Movement Disorder Society Unified Parkinson\u0026rsquo;s Disease Rating Scale (MDS-UPDRS, Parts I\u0026ndash;III). In addition, cognitive function was screened using the Montreal Cognitive Assessment (MoCA),\u003csup\u003e17\u003c/sup\u003e and the Innsbruck REM Sleep Behavior Disorder Inventory (RBD-I) was used to identify symptoms suggestive of RBD, with a cutoff score of \u0026ge;\u0026thinsp;0.25 indicating probable RBD.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e Olfactory function was assessed using the Identification (SSI) and Discrimination (SSD) subtests of Sniffin\u0026rsquo; Sticks test battery (Burghart Medizintechnik, Wedel, Germany). To minimize cross-infection risk during the COVID-19 pandemic, odors were presented using a single-use paper sheet to which the tip of the reusable odor pen had been applied, in accordance with the recommendations of the German Society of Otorhinolaryngology, Head and Neck Surgery; consequently, the threshold subtest was omitted because it could not be safely administered under these conditions.\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eAge- and sex-adjusted normative reference values were used, applying the 10th percentile of the Identification subtest as the cut-off for hyposmia screening.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003ch3\u003eOM sampling and RT-QuIC\u003c/h3\u003e\n\u003cp\u003eOlfactory mucosa (OM) samples were collected by ENT specialists medial of the middle nasal turbinate in the direction of the superior nasal turbinate using FLOQ-Brushes (Copan Italia).\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e Following the OM collection, swabs were stored at 4\u0026deg;C, and shipped on dry ice to the University of Verona for processing and aSyn-SAA analysis, as previously published.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eIn particular, recombinant full-length human α-synuclein (aSyn; amino acids 1\u0026ndash;140) was prepared in-house. aSyn cDNA was cloned into pET-28a and expressed in E. coli BL21 (DE3). After induction with 0.1 mM IPTG, the periplasmic fraction was isolated, subjected to ammonium sulfate precipitation, and further purified via anion-exchange chromatography (Q-Sepharose, GE Healthcare). Protein purity was verified by SDS-PAGE, and aliquots were dialyzed into 10 mM sodium phosphate buffer (pH 7.4) and stored at \u0026minus;\u0026thinsp;80\u0026deg;C.\u003c/p\u003e \u003cp\u003eFor aSyn-SAA, 2 \u0026micro;L of diluted OM homogenate was incubated in 98 \u0026micro;L reaction buffer (100 mM phosphate buffer, pH 8.2; 10 \u0026micro;M Thioflavin T; 0.1 mg/mL recombinant aSyn; 0.004% SDS) containing\u0026thinsp;~\u0026thinsp;37 mg of 0.5 mm glass beads. Reactions were run in triplicate at 30\u0026deg;C in a FLUOstar\u0026reg; Omega plate reader under cycles of shaking (1 min at 200 rpm, double orbital) and rest (14 min), with fluorescence recorded every 45 min (excitation 450\u0026thinsp;\u0026plusmn;\u0026thinsp;10 nm, emission 480\u0026thinsp;\u0026plusmn;\u0026thinsp;10 nm).\u003c/p\u003e \u003cp\u003eA reaction was considered positive if fluorescence exceeded 10% of the plate\u0026rsquo;s maximum signal. OM samples were classified as positive if\u0026thinsp;\u0026ge;\u0026thinsp;2 of 3 replicates crossed this threshold within 50 h, negative if none did, and inconclusive if one of three was positive. Inconclusive samples were reanalyzed and, if results persisted, classified as negative.\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003ch3\u003eStatistics\u003c/h3\u003e\n\u003cp\u003eAll statistical analyses were performed using IBM SPSS Statistics (version 29.0; IBM Corp., Armonk, NY, USA). Age, sex and OM-SAA results were compared among people with PD, individuals with post-COVID-19, and HC. Group comparisons were performed using chi-square tests with Benjamini\u0026ndash;Hochberg FDR-corrected post-hoc analyses, and a univariate ANOVA followed by Šid\u0026aacute;k-corrected post-hoc tests. As the PD cohort was included as a positive control group for the OM-SAA, the PD cohort was not included for further group comparisons.\u003c/p\u003e \u003cp\u003eChi-square tests were applied to assess differences in categorical variables (e.g., sex, persistent hyposmia, OM-SAA positivity) among COVID\u0026thinsp;+\u0026thinsp;OD, COVID-OD, and HC. Group differences in OM-SAA positivity were analyzed using contingency-table statistics. Counts of OM-SAA\u0026ndash;positive and \u0026ndash;negative individuals were cross-tabulated across three groups (COVID\u0026thinsp;+\u0026thinsp;OD, COVID-OD, and HC). The overall association between group and OM-SAA status was assessed using a two-sided chi-square test of independence (2\u0026times;3 design), with post-hoc comparisons corrected using the Benjamini\u0026ndash;Hochberg FDR procedure; expected cell counts satisfied assumptions for χ\u0026sup2; approximation. Effect size was reported as Cramer\u0026rsquo;s V. To complement these analyses, column-proportion tests with z-statistic annotation were applied for descriptive pairwise comparisons, where groups sharing the same subset label did not differ significantly at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. To account for age differences across groups, we conducted a multivariable logistic regression predicting OM-SAA positivity, entering age and sex as covariates. Model significance was assessed using the omnibus χ\u0026sup2; statistic, and effects are expressed as odds ratios (95% CI). Additionally, OM-SAA positivity was modelled using multivariable logistic regression for those contrasts identified as significant in the chi-square analysis, with age and sex included as covariates and p-values adjusted via Benjamini\u0026ndash;Hochberg FDR correction. Continuous outcomes (e.g., MoCA and MDS-UPDRS scores) were analyzed using analysis of covariance (ANCOVA) models controlling for age and sex, with post-hoc comparisons corrected using the Šid\u0026aacute;k procedure.\u003c/p\u003e \u003cp\u003eWithin the post-COVID cohort, differences between participants with and without positive OM-SAA results, were assessed for key demographic and clinical measures. To account for potential confounding by age and sex, analysis of covariance (ANCOVA) models was applied to these continuous outcomes.\u003c/p\u003e \u003cp\u003eDemographic and clinical variables were summarized as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviations (SD) for continuous measures and as absolute and relative frequencies for categorical variables. Adjusted means from the ANCOVA models are reported with 95% confidence intervals (CI).\u003c/p\u003e \u003cp\u003eDue to the lack of existing prevalence data regarding OM-SAA of COVID-19 patients and significant uncertainty regarding their prevalence in HC, a formal power calculation was not conducted. The study was designed as an exploratory pilot to inform future research. The significance threshold was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 (two-sided, unless stated otherwise). For multiple comparisons, Benjamini\u0026ndash;Hochberg FDR correction was applied to chi-square and multivariable logistic regression analyses, and the Šid\u0026aacute;k procedure was used for ANOVA and ANCOVA, with all p-values referring to the adjusted level unless otherwise stated.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 191 participants were included: 51 PD patients, 98 post-COVID-19 participants (44 with COVID\u0026thinsp;+\u0026thinsp;OD: n\u0026thinsp;=\u0026thinsp;44, and COVID\u0026ndash;OD: n\u0026thinsp;=\u0026thinsp;54), and 42 HC. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes demographic and OM-SAA results for all study groups. OM-SAA was positive in 80.4% of PD, 23.5% of post-COVID, and 11.9% of HC participants (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). PD differed significantly from both post-COVID and HC (both p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), whereas the difference between post-COVID and HC was not significant.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographic and OM-SAA results across study groups.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHC\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCOVID-19\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;98)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePD\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;51)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep-value*\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (m:f) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20:22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e47:51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32:19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.190:\u003c/p\u003e \u003cp\u003e0.971/0.216/0.258\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44.83\u0026plusmn;12.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e49.37\u0026plusmn;17.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e69.37\u0026plusmn;9.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001:\u003c/p\u003e \u003cp\u003e0.278/\u0026lt;0.001/\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOM-SAA positivity (%) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (11.91)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23 (23.47)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e41 (80.39)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001:\u003c/p\u003e \u003cp\u003e0.117/\u0026lt;0.001/\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eThe significance level is set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. Post-hoc p-values were adjusted using Benjamini\u0026ndash;Hochberg FDR correction for chi-square and Šid\u0026aacute;k correction for ANOVA; all reported p-values are adjusted.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e* p-value for overall group comparison: HC versus COVID-19/HC versus PD/COVID-19 versus PD.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003csup\u003ea\u003c/sup\u003e Chi-square test.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003csup\u003eb\u003c/sup\u003e univariate one-way analysis of variance, ANOVA.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eClinical and OM-SAA outcomes in the post-COVID-19 cohorts (Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographic and Clinical Variables as well as OM-SAA results in the post-COVID cohorts and healthy controls.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eHC (n\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eCOVID-OD (n\u0026thinsp;=\u0026thinsp;54)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eCOVID\u0026thinsp;+\u0026thinsp;OD (n\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep-value*\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (m:f) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e20:22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e25:29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e22:22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.935:\u003c/p\u003e \u003cp\u003e0.897 /0.897 /0.897\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e44.83\u0026plusmn;12.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e43.30\u0026plusmn;16.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e56.82\u0026plusmn;16.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001:\u003c/p\u003e \u003cp\u003e0.951/ 0.002/ \u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMonths since COVID-19 \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eNA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e16.89\u0026plusmn;10.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e17.39\u0026plusmn;9.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.806\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOM-SAA positivity (%) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e5 (11.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e8 (14.8.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e15 (34.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.018:\u003c/p\u003e \u003cp\u003e0.679/0.038/0.038\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003emean\u0026plusmn;SD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003emean\u003c/b\u003e\u003csub\u003e\u003cb\u003eadj\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(96%CI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003emean\u0026plusmn;SD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003emean\u003c/b\u003e\u003csub\u003e\u003cb\u003eadj\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(96%CI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003emean\u0026plusmn;SD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003emean\u003c/b\u003e\u003csub\u003e\u003cb\u003eadj\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(96%CI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSSI \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.76\u0026plusmn;1.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.65\u003c/p\u003e \u003cp\u003e(14.27\u0026ndash;15.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.80\u0026plusmn;1.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14.62\u003c/p\u003e \u003cp\u003e(14.29\u0026ndash;14.95)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.48\u0026plusmn;1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.38\u003c/p\u003e \u003cp\u003e(8.42\u0026ndash;9.19)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001:\u003c/p\u003e \u003cp\u003e0.999/ \u0026lt;0.001/ \u0026lt;0.001\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSSD \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.83\u0026plusmn;1.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.72\u003c/p\u003e \u003cp\u003e(14.12\u0026ndash;15.33)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13.83\u0026plusmn;2.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e13.67\u003c/p\u003e \u003cp\u003e(13.14\u0026ndash;14.21)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10.32\u0026plusmn;2.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10.62\u003c/p\u003e \u003cp\u003e(10.00-11.23)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001:\u003c/p\u003e \u003cp\u003e0.030/ \u0026lt;0.001/ \u0026lt;0.001\u003c/p\u003e\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMoCA \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29.33\u0026plusmn;0.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29.17\u003c/p\u003e \u003cp\u003e(28.77\u0026ndash;29.57)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e28.88\u0026plusmn;1.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28.65\u003c/p\u003e \u003cp\u003e(28.29-29.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e27.93\u0026plusmn;1.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28.38\u003c/p\u003e \u003cp\u003e(27.98\u0026ndash;28.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.021:\u003c/p\u003e \u003cp\u003e0.142/ 0.022/ 0.710\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS I \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.50\u0026plusmn;1.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.71\u003c/p\u003e \u003cp\u003e(-0.35-1.77)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.70\u0026plusmn;3.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.02\u003c/p\u003e \u003cp\u003e(1.08\u0026ndash;2.96)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.55\u0026plusmn;5.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.96\u003c/p\u003e \u003cp\u003e(1.88\u0026ndash;4.03)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.060:\u003c/p\u003e \u003cp\u003e0.188/ 0.013/ 0.509\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS II \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.00\u0026plusmn;0.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003cp\u003e(-0.50-0.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.35\u0026plusmn;1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003cp\u003e(-0.03-1.07)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.25\u0026plusmn;3.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.93\u003c/p\u003e \u003cp\u003e(0.30\u0026ndash;1.56)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.199:\u003c/p\u003e \u003cp\u003e0.697/ 0.204/ 0.719\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS III \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.60\u0026plusmn;1.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.95\u003c/p\u003e \u003cp\u003e(-0.33-2.22)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.15\u0026plusmn;3.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.66\u003c/p\u003e \u003cp\u003e(0.52\u0026ndash;2.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.09\u0026plusmn;7.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.13\u003c/p\u003e \u003cp\u003e(1.83\u0026ndash;4.43)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.066:\u003c/p\u003e \u003cp\u003e0.797/ 0.064/ 0.279\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS total \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.02\u0026plusmn;1.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.70\u003c/p\u003e \u003cp\u003e(-0.88-4.28)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.20\u0026plusmn;7.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.19\u003c/p\u003e \u003cp\u003e(1.89\u0026ndash;6.49)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.89\u0026plusmn;13.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.03\u003c/p\u003e \u003cp\u003e(4.40\u0026ndash;9.65)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.021:\u003c/p\u003e \u003cp\u003e0.391/ 0.017 0.320\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRBD-I score \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.10\u0026plusmn;0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003cp\u003e(-0.09-0.34)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.19\u0026plusmn;0.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003cp\u003e(0.04\u0026ndash;0.42)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.45\u0026plusmn;1.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003cp\u003e(0.15\u0026ndash;0.59)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.598:\u003c/p\u003e \u003cp\u003e0.851/ 0.735/ 0.328\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eThe significance level is set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. Post-hoc p-values were adjusted using Benjamini\u0026ndash;Hochberg FDR correction for chi-square and logistic regression analyses and Šid\u0026aacute;k correction for ANOVA/ANCOVA; all reported p-values are adjusted.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e* p-value for overall group comparison: HC versus COVID-OD/HC versus COVID\u0026thinsp;+\u0026thinsp;OD/COVID-OD versus COVID\u0026thinsp;+\u0026thinsp;OD.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003csup\u003ea\u003c/sup\u003e Chi-square test.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003csup\u003eb\u003c/sup\u003e univariate one-way analysis of variance, ANOVA.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003csup\u003ec\u003c/sup\u003e independent two-sample t-test.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003csup\u003ed\u003c/sup\u003e univariate analysis of covariance (ANCOVA) corrected for age and sex (mean\u003csub\u003eadj\u003c/sub\u003e, adjusted mean derived from univariate ANCOVA with age and sex as covariates).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e summarizes demographic, clinical and olfactory data as well as OM-SAA results between HC and the post-COVID-19 groups.\u003c/p\u003e \u003cp\u003eAcross the 140 individuals from the HC and post-COVID-19 cohorts, OM-SAA positivity was detected in 20.0% of cases (28/140). OM-SAA positivity rates differed across groups, with 11.9% in HC, 34.1% in COVID\u0026thinsp;+\u0026thinsp;OD, and 14.8% in COVID-OD. A chi-square test of independence confirmed a significant overall association between diagnostic group and OM-SAA status (χ\u0026sup2;(2)\u0026thinsp;=\u0026thinsp;8.09, p\u0026thinsp;=\u0026thinsp;0.018), corresponding to a small-to-medium effect (Cramer\u0026rsquo;s V\u0026thinsp;=\u0026thinsp;0.24). OM-SAA positivity was significantly higher in COVID\u0026thinsp;+\u0026thinsp;OD compared with both, HC and COVID-OD (both p\u0026thinsp;=\u0026thinsp;0.038), while no difference was observed in COVID-OD relative to HC. After applying Benjamini\u0026ndash;Hochberg FDR adjustment, only contrasts involving COVID\u0026thinsp;+\u0026thinsp;OD remained significant. Post-hoc z-based column-proportion tests reproduced this pattern, indicating higher positivity exclusively in COVID\u0026thinsp;+\u0026thinsp;OD, while HC and COVID-OD did not differ. Moreover, when comparing COVID\u0026thinsp;+\u0026thinsp;OD participants with COVID\u0026thinsp;\u0026minus;\u0026thinsp;OD participants and HC, olfactory dysfunction remained significantly associated with OM-SAA positivity after adjustment for age and sex (omnibus χ\u0026sup2;(4)\u0026thinsp;=\u0026thinsp;9.91, p\u0026thinsp;=\u0026thinsp;0.042, R\u0026sup2;=0.108). Group allocation was the only significant predictor in the overall model, with higher odds of OM-SAA positivity in COVID\u0026thinsp;+\u0026thinsp;OD relative to HC (OR\u0026thinsp;=\u0026thinsp;3.84, 95% CI 1.17\u0026ndash;12.57, β\u0026thinsp;=\u0026thinsp;1.35, SE\u0026thinsp;=\u0026thinsp;0.61, p\u0026thinsp;=\u0026thinsp;0.026) and COVID\u0026thinsp;+\u0026thinsp;OD (OR\u0026thinsp;=\u0026thinsp;2.95, 95% CI 1.02\u0026ndash;8.52, β\u0026thinsp;=\u0026thinsp;1.08, SE\u0026thinsp;=\u0026thinsp;0.54, p\u0026thinsp;=\u0026thinsp;0.046), whereas age and sex showed no effects. Additionally, OD remained significantly associated with OM-SAA positivity after adjustment for age and sex when comparing COVID\u0026thinsp;+\u0026thinsp;OD with HC (OR\u0026thinsp;=\u0026thinsp;3.58, 95% CI 1.05\u0026ndash;12.25; β\u0026thinsp;=\u0026thinsp;1.25, SE\u0026thinsp;=\u0026thinsp;0.63) and when comparing COVID\u0026thinsp;+\u0026thinsp;OD with COVID\u0026ndash;OD participants (OR\u0026thinsp;=\u0026thinsp;3.07, 95% CI 1.03\u0026ndash;9.12; β\u0026thinsp;=\u0026thinsp;1.12, SE\u0026thinsp;=\u0026thinsp;0.56), with both comparisons yielding p\u0026thinsp;=\u0026thinsp;0.044. These results are consistent with the categorical analyses, indicating that OM-SAA positivity is selectively elevated in the COVID\u0026thinsp;+\u0026thinsp;OD group.\u003c/p\u003e \u003cp\u003eTo test whether there were group differences in the continuous clinical variables between healthy controls and post-COVID groups, we conducted univariate ANCOVAs with age and sex as covariates. After adjustment, MoCA scores differed significantly between groups (F\u0026thinsp;=\u0026thinsp;3.97, p\u0026thinsp;=\u0026thinsp;0.021, partial η\u0026sup2;=0.056; overall model fit: R\u0026sup2;=0.376, adjusted R\u0026sup2;=0.357). Age showed a strong association with MoCA performance (F\u0026thinsp;=\u0026thinsp;49.78, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, partial η\u0026sup2;=0.269), whereas sex did not (F\u0026thinsp;=\u0026thinsp;2.31, p\u0026thinsp;=\u0026thinsp;0.131). Post-hoc comparisons indicated that this effect was driven by lower MoCA scores in the COVID\u0026thinsp;+\u0026thinsp;OD compared to the HC group (p\u0026thinsp;=\u0026thinsp;0.022). Similarly, after adjustment, there was a significant association of MDS-UPDRS-total scores (F\u0026thinsp;=\u0026thinsp;3.95, p\u0026thinsp;=\u0026thinsp;0.021, partial η\u0026sup2;=0.055; overall model fit: R\u0026sup2;=0.241; adj. R\u0026sup2;=0.218) with groups. Age was strongly associated with MDS-UPDRS-total scores (F\u0026thinsp;=\u0026thinsp;21.78, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, partial η\u0026sup2;=0.139), whereas sex was not (F\u0026thinsp;=\u0026thinsp;1.38, p\u0026thinsp;=\u0026thinsp;0.242). Post-hoc comparisons indicated that this effect was driven by higher MDS-UPDRS-total scores in the COVID\u0026thinsp;+\u0026thinsp;OD relative to the healthy control group (p\u0026thinsp;=\u0026thinsp;0.017). This was driven by higher MDS-UPDRS I scores in the COVID\u0026thinsp;+\u0026thinsp;OD cohort (F\u0026thinsp;=\u0026thinsp;4.29, p\u0026thinsp;=\u0026thinsp;0.016, partial η\u0026sup2;=0.060; see Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), while MDS-UPDRS-II (F\u0026thinsp;=\u0026thinsp;1.63, p\u0026thinsp;=\u0026thinsp;0.199) and -III (F\u0026thinsp;=\u0026thinsp;2.78, p\u0026thinsp;=\u0026thinsp;0.066) did not differ between groups.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eOlfactory and Clinical Outcomes by OM-SAA Positivity (Table 3)\u003c/h3\u003e\n\u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePost-COVID Participants With vs. Without Positive OM SAA Activity.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eaSyn-SAA negative (n\u0026thinsp;=\u0026thinsp;75)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eaSyn-SAA positive (n\u0026thinsp;=\u0026thinsp;23)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ep-value\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (m:f) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e32:43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e15:8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.058\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eage \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e48.33\u0026plusmn;17.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e52.74\u0026plusmn;18.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.306\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emean\u0026plusmn;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003emean\u003csub\u003eadj\u003c/sub\u003e (96%CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003emean\u0026plusmn;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003emean\u003csub\u003eadj\u003c/sub\u003e (96%CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSSI \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.53\u0026plusmn;3.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.42 (11.77\u0026ndash;13.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.09\u0026plusmn;3.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.43 (9.23\u0026ndash;11.64)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSSD \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.73\u0026plusmn;2.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.68 (12.12\u0026ndash;13.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.70\u0026plusmn;3.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.87 (9.84\u0026ndash;11.90)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS I \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.31\u0026plusmn;4.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.40 (1.46\u0026ndash;3.34)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.26\u0026plusmn;3.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.95 (1.24\u0026ndash;4.67)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.580\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS II \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.84\u0026plusmn;2.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.87 (0.33\u0026ndash;1.42)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.48\u0026plusmn;1.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.37 (-0.63-1.37)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.388\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS III \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.55\u0026plusmn;6.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.58 (1.46\u0026ndash;3.70)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.22\u0026plusmn;2.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.12 (0.07\u0026ndash;4.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.700\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMDS-UPDRS total \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.69\u0026plusmn;12.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.85 (3.55\u0026ndash;8.15)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.96\u0026plusmn;5.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.44 (1.25\u0026ndash;9.64)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.867\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMoCA \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28.63\u0026plusmn;1.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e28.55 (28.22\u0026ndash;28.87)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27.91\u0026plusmn;2.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28.18 (27.58\u0026ndash;28.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.292\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRBD score \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.24\u0026plusmn;0.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.26 (0.07\u0026ndash;0.45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.52\u0026plusmn;0.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.47 (0.12\u0026ndash;0.81)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.294\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eThe significance level is set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u003csup\u003ea\u003c/sup\u003e Chi-square test.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u003csup\u003eb\u003c/sup\u003e univariate one-way analysis of variance, ANOVA.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u003csup\u003ec\u003c/sup\u003e univariate analysis of covariance (ANCOVA) corrected for age and sex (mean\u003csub\u003eadj\u003c/sub\u003e, adjusted mean derived from univariate ANCOVA with age and sex as covariates).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eAbbreviations: aSyn, alpha-synuclein; COVID-OD, post-covid cohort without persistent olfactory dysfunction; COVID\u0026thinsp;+\u0026thinsp;OD, post-COVID cohort with persistent olfactory dysfunction; HC, healthy controls; MDS-UPDRS, Movement Disorders Unified Disease Parkinson\u0026rsquo;s Rating Scale; MoCA, Montreal Cognitive Assessment; n, number; OM-SAA, olfactory mucosa seeding amplification assay; RBD-I, Innsbruck RBD Inventory; SD, standard deviation; SSD, Sniffin\u0026rsquo; Sticks Discrimination test; SSI, Sniffin\u0026rsquo; Sticks Identification test.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTo test whether OM-SAA positivity was associated with olfactory function, we conducted a univariate ANCOVA with age and sex as covariates. After adjustment, OM-SAA positive participants showed significantly lower Sniffin\u0026rsquo; Sticks Identification scores than OM-SAA negative individuals (F\u0026thinsp;=\u0026thinsp;8.18, p\u0026thinsp;=\u0026thinsp;0.005, partial η\u0026sup2;=0.080; overall model fit: R\u0026sup2;=0.345, adjusted R\u0026sup2;=0.324). Age was strongly associated with Sniffin\u0026rsquo; Sticks Identification performance (F\u0026thinsp;=\u0026thinsp;35.92, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, partial η\u0026sup2;=0.276), whereas sex was not (F\u0026thinsp;=\u0026thinsp;0.03, p\u0026thinsp;=\u0026thinsp;0.874). For Sniffin\u0026rsquo; Sticks discrimination, OM-SAA positive individuals likewise showed significantly lower scores than OM-SAA negative participants (F\u0026thinsp;=\u0026thinsp;9.23, p\u0026thinsp;=\u0026thinsp;0.003, partial η\u0026sup2;=0.089; overall model fit: R\u0026sup2;=0.296; adjusted R\u0026sup2;=0.274). Age was again a strong predictor of performance (F\u0026thinsp;=\u0026thinsp;27.27, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, partial η\u0026sup2;=0.225), whereas sex showed no significant association (F\u0026thinsp;=\u0026thinsp;0.69, p\u0026thinsp;=\u0026thinsp;0.409). As summarized in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, no significant associations were observed between OM-SAA positivity and MDS-UPDRS total or subscores, MoCA, or RBD-I scores.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this pilot study OM aSyn seeding activity was detected in approximately one-third of individuals with persistent OD after COVID-19, while OM-SAA positivity rates in post-COVID participants without OD were similar to HC (14.8% vs 11.9%) and thus overall consistent with previous studies.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e As expected, OM-SAA positivity rate was high in participants with PD (80.4%) and well within the upper range of previously reported studies using the OM matrix.\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e Although overall OM-SAA positivity did not differ significantly between the entire post-COVID cohort and HC, the higher rate among participants with persistent OD suggests that SARS-CoV-2\u0026ndash;related injury to the olfactory mucosa may trigger local aSyn misfolding in the context of inflammation. Whether such peripheral aSyn aggregation can persist and propagate centrally and eventually cause clinically manifest PD or other synucleinopathy remains speculative.\u003c/p\u003e \u003cp\u003eMoreover, COVID\u0026thinsp;+\u0026thinsp;OD participants showed lower MoCA and higher MDS-UPDRS total scores, with the latter being most plausibly driven by increased MDS-UPDRS-I scores. While causality cannot be inferred from the present data, this pattern may be compatible with reports suggesting that persistent post-COVID OD can co-occur with broader neuropsychiatric sequelae \u0026mdash; including fatigue, affective symptoms, sleep disturbances, and cognitive impairment.\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eExperimental studies have shown detrimental effects of SARS-CoV-2 on substantia nigra dopaminergic neurons as well as stem cell derived dopaminergic neurons,\u003csup\u003e26\u0026ndash;28\u003c/sup\u003e and SARS-CoV-2 induced neuroinflammation has been suggested to trigger aSyn misfolding and aggregation with a potential to aggravate or induce a-synucleinopathies.\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eAlthough the observation of increased rates of OM-SAA positivity in post-COVID-19 subjects with persistent OD seems biologically plausible given SARS-CoV-2 olfactory tropism and the pro-aggregatory potential of neuroinflammation,\u003csup\u003e8,10,11\u003c/sup\u003e the present results are insufficient to conclude on the prognostic relevance of this finding. Longterm follow-up will be needed to shed light on this evidence and to determine whether post-infectious OM-SAA positivity represents a transient observation or a persistent finding.\u003c/p\u003e \u003cp\u003eWhile the assessment of OM-SAA positivity in individuals with a history of SARS-CoV-2 infection together with objective olfactory and clinical phenotyping are strengths of this study; it is still limited by the small sample size of post-COVID subjects, the difficulty of recruiting COVID-na\u0026iuml;ve HC due to the increasing prevalence of SARS-CoV-2 exposure and previous infections in the general population over time, and the cross-sectional design. Furthermore, we cannot fully exclude that some HC may have had an unrecognized (\u0026lsquo;silent\u0026rsquo;) prior SARS-CoV-2 infection, since nucleocapsid antibody testing\u0026mdash;which would allow discrimination between infection- and vaccination-induced seroreactivity\u0026mdash;was introduced at our institution only after HC recruitment had been completed.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOM-SAA positivity was enriched among individuals with persistent post-COVID OD and correlated with olfactory impairment. Whether this finding reflects a transient post-infectious phenomenon or an early synucleinopathy signature remains to be determine.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCOVID-OD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003epost-covid cohort without persistent olfactory dysfunction\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCOVID\u0026thinsp;+\u0026thinsp;OD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003epost-COVID cohort with persistent olfactory dysfunction\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eHC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ehealthy controls\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMDS-UPDRS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMovement Disorders Unified Disease Parkinson\u0026rsquo;s Rating Scale\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMoCA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMontreal Cognitive Assessment\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003en\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003enumber\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eOM-SAA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eolfactory mucosa seeding amplification assay\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eRBD-I\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInnsbruck RBD Inventory\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003estandard deviation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSSD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSniffin\u0026rsquo; Sticks Discrimination test\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSSI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSniffin\u0026rsquo; Sticks Identification test.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eAustrian Science Fund (FWF) Clinical Research project \u003cb\u003eKLI 1037-B\u003c/b\u003e.\u003c/p\u003e\u003ch2\u003eAuthor contributions\u003c/h2\u003e \u003cp\u003eWP conceived the study, initiated the research idea, and substantially contributed to the conceptual design in early discussions with collaborators. BH directed the study, coordinated its implementation, and supervised data collection. KS made major contributions to the research idea, contributed to study design, clinical oversight, and patient phenotyping. JS and TG performed the ENT procedures and OM sampling. MB, EB, and GZ conducted and supervised the RT-QuIC analyses in Verona. BH, NDC, KS, and CC managed, curated, and organized the clinical and laboratory data. BH, KS, NDC, FJ, PK, and JLR contributed to clinical assessments, recruitment, and data acquisition. GW provided infectious-disease expertise and oversight during recruitment and clinical characterization.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThe authors are grateful to all participants for their personal commitment to make this study possible\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eAll de-identified data supporting the findings of this study will be made openly available in a public data repository upon publication. A persistent link and DOI will be provided in the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBraak H, Del Tredici K, R\u0026uuml;b U et al (2003) Staging of brain pathology related to sporadic Parkinson's disease. 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Int J Mol Sci 25:12079. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/ijms252212079\u003c/span\u003e\u003cspan address=\"10.3390/ijms252212079\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBoura I, Qamar MA, Daddoveri F et al (2023) SARS-CoV-2 and Parkinson's Disease: A Review of Where We Are Now. Biomedicines 11:2524. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/biomedicines11092524\u003c/span\u003e\u003cspan address=\"10.3390/biomedicines11092524\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi H, Qian J, Wang Y et al (2024) Potential convergence of olfactory dysfunction in Parkinson's disease and COVID-19: The role of neuroinflammation. Ageing Res Rev 97:102288. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.arr.2024.102288\u003c/span\u003e\u003cspan address=\"10.1016/j.arr.2024.102288\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"COVID-19, olfaction, olfactory mucosa, α-synuclein, RT-QuIC, Parkinson’s disease, hyposmia","lastPublishedDoi":"10.21203/rs.3.rs-8855629/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8855629/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eOlfactory dysfunction (OD) is a hallmark of SARS-CoV-2-infection where it is believed to result from neuroinflammation induced by viral invasion via the olfactory mucosa (OM). Hyposmia also affects the majority of patients with Parkinson\u0026rsquo;s disease (PD) where it is caused by α-synuclein (aSyn) pathology in the olfactory system, and aSyn-seeding-activity can be detected in the OM using aSyn-seeding-amplification-assays (aSyn-SAA). The present pilot study aimed to investigate whether SARS-CoV-2-infection induces local aSyn-misfolding and -aggregation in OM samples using aSyn-SAA.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eWe conducted an observational study including PD patients (n\u0026thinsp;=\u0026thinsp;51), individuals with a history of documented symptomatic SARS-CoV-2-infection (post-COVID; n\u0026thinsp;=\u0026thinsp;98), and healthy controls (HC; n\u0026thinsp;=\u0026thinsp;42). Post-COVID-participants were stratified based on persistent OD (COVID\u0026thinsp;+\u0026thinsp;OD; n\u0026thinsp;=\u0026thinsp;44) or normal olfaction (COVID\u0026ndash;OD; n\u0026thinsp;=\u0026thinsp;54) using Sniffin\u0026rsquo;-Sticks-Identification (SSI) and -Discrimination (SSD) tests. OM samples were obtained by ENT specialists and analyzed by aSyn-SAA at the University of Verona. Clinical phenotyping included MDS-UPDRS, MoCA, and the Innsbruck-RBD-Inventory.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eOM-SAA positivity rates were significantly different between PD and both post-COVID-participants and HCs (80.4% vs 23.4% vs 11.9%; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Within the post-COVID-group, positivity rates were higher in COVID\u0026thinsp;+\u0026thinsp;OD vs COVID\u0026ndash;OD (34.1% vs 14.8%; p\u0026thinsp;=\u0026thinsp;0.038), and COVID\u0026thinsp;+\u0026thinsp;OD differed from HC (p\u0026thinsp;=\u0026thinsp;0.038), while COVID\u0026ndash;OD did not (p\u0026thinsp;=\u0026thinsp;0.679). Among post-COVID-participants, aSyn-SAA positivity was associated with lower SSI (p\u0026thinsp;=\u0026thinsp;0.005) and SSD (p\u0026thinsp;=\u0026thinsp;0.003) scores, but not with MDS-UPDRS, MoCA, or RBD measures.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eOM-SAA-positivity was enriched among individuals with persistent post-COVID-OD and correlated with olfactory impairment. These findings support the hypothesis that neuroinflammation following SARS-COV-2-infection might promote local aSyn-aggregation. The biological and prognostic relevance of OM-SAA positivity is unknown and needs further prospective investigation.\u003c/p\u003e","manuscriptTitle":"Prevalence of Alpha-Synuclein Seeding Activity in the Olfactory Mucosa following SARS-CoV-2 Infection - Results from a Pilot Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-04 09:18:42","doi":"10.21203/rs.3.rs-8855629/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b18c095a-3884-410b-bc8b-35657ec0e8bd","owner":[],"postedDate":"March 4th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":62895430,"name":"Health sciences/Neurology/Neurological disorders/Neurodegenerative diseases/Parkinson's disease"},{"id":62895431,"name":"Health sciences/Risk factors"}],"tags":[],"updatedAt":"2026-04-23T16:35:40+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-04 09:18:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8855629","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8855629","identity":"rs-8855629","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}