Olfactory Dysfunction Research Articles

A Pilot Study of the Computerized Brief Smell Identification Test

Objectives: A self-administered Computerized Brief Smell Identification Test (cB-SIT) was developed recently to perform the olfactory identification test under computer control. The aim of this study was to evaluate the clinical applicability of the cB-SIT as compared with the traditional Brief Smell Identification Test (B-SIT). Methods: Sixty healthy volunteers with self-reported normal olfactory function, 30 hyposmic patients, and 30 anosmic patients were enrolled from June 2023 to May 2024. All enrolled participants received both B-SIT and cB-SIT in a random order to measure their odor identification ability. Thirty healthy volunteers took the second B-SIT and cB-SIT at least one week later. Results: The score was significantly different in both B-SIT and cB-SIT among healthy volunteers, hyposmic, and anosmic patients. The correct answer rate was significantly different in 10 items of the B-SIT and in 7 items of the cB-SIT among the three groups, but the post hoc test showed significant differences in correct answer rates between healthy volunteers and hyposmic patients in 7 items of both the B-SIT and cB-SIT. Test–retest results showed the score of the second B-SIT test was significantly higher than that of the first test, but the scores of the two tests of the cB-SIT were not significantly different. In the B-SIT, the lemon odorant had a higher correct answer rate in the second test than in the first test, but in the cB-SIT, the correct answer rate was not significantly different between the first and second tests in all 12 items. Conclusions: Our findings demonstrate that the cB-SIT was similar to the B-SIT and can be administered in the diagnosis of patients with olfactory dysfunction.

Effect of Intranasal Insulin on Olfactory Recovery in Patients with Anosmia .

Olfactory dysfunction, defined as either a complete or partial impairment of smell, is a common condition that may substantially affect a person’s quality of life and is frequently difficult to treat. Physical activity, heredity, nutrition, smoking, head trauma, medical treatments, and virus exposure all influence one’s capacity to smell. Hyposmia or anosmia, or loss of smell, affects 3% to 20% of the population. Intranasal insulin can improve cognitive performance, reduce food intake, and boost olfactory thresholds in healthy individuals. As people age, they are more likely to experience olfactory dysfunction, which may be affected by a variety of reasons, such as acute and chronic sino-nasal illness, upper respiratory infections, toxic chemical exposure, and degenerative diseases. About ten percent of those over 65 develop olfactory impairment, which can range from mild loss to total anosmia. Insulin resistance in the central nervous system has been linked to conditions like type II diabetes, Alzheimer’s disease, obesity, and poor odor identification. Reduced odor perception may contribute to reduced olfactory function in anosmic patients.

Association between urinary mixture metal levels and olfactory function in coal miners.

Exposure to occupational metallic mixtures has a potential impact on olfactory function. However, research evidence is limited on the potential impact of exposure to metallic mixtures and olfactory dysfunction. Furthermore, the coal dust generated contains multiple various metals during coal mining, and no study yet has focus on the olfactory dysfunction of coal miners. In this study, we evaluate the association between urinary metallic mixtures and olfactory function in coal miners, while also exploring the potential applicability of plasma olfactory marker protein (OMP) as a biomarker for assessing olfaction. From July to October 2023, coal workers from seven different coal mining enterprises were recruited for the survey when they come for the employee health checkup. Ultimately, 376 participants were met the inclusion criteria and, respectively, determined with the concentrations of urine (16 metals) and plasma (OMP). Meanwhile, applying UPSIT to access their olfactory function. Binary logistic regression and restricted cubic spline (RCS) model were used to estimate the association of individual metals with olfactory function. Bayesian kernel machine regression (BKMR) and Quantile g-computation (QG-C) regression were employed to assess the overall association between metal mixtures and olfactory function and identify the major contributing elements. In a single-metal model, two metals in urine were found to be significantly associated with olfactory function. RCS analysis further revealed that the association between Iron (Fe) and olfactory function was linear, while Lead (Pb) exhibited a non-linear. The BKMR model demonstrated a significant positive association between metal mixture concentration and olfactory function. Combined QG-C regression analysis suggested that metals Cr, Fe, Se, Sb, and Pb could impact the performance of the olfactory test (UPSIT), with Pb being identified as the most influential contributor. The correlation between plasma OMP protein levels and urinary metal concentrations was weak. Multiple metals are associated with olfactory function in the coal miners. A significant positive association was observed between metal mixture concentrations and olfactory function, with Pb being the most important contributor. In this study, plasma OMP has not been demonstrated to serve as a biomarker for olfactory function.

Unlocking the Secrets: Predictive Risk Factors for Long-term Olfactory Dysfunction in COVID-19 Patients

<b>Introduction:</b> COVID-19 is a multisystem disease that can severely impact overall health. It causes non-lethal complications that may significantly affect the quality of life, such as smell dysfunction, which has been identified as an essential and early indicator of infection. A substantial proportion suffer from prolonged or even permanent loss of smell.<b>Aim:</b> The study aims to identify key clinical and demographic risk factors that significantly predict the prognosis of such an olfactory loss in patients with COVID-19.<b>Materials and method:</b> A prospective, cross-sectional, descriptive study. Qualified patients were aged ≥ 18 years with a past COVID-19 infection confirmed by PCR. They all underwent thorough clinical assessments and nasoendoscopy to exclude other nasal pathologies. The Alcohol Threshold Test (ATT) was used to assess olfactory function and only patients with severe hyposmia and anosmia were included in the study. The Arabic version of the Kessler Psychological Distress Scale (K10) was used to assess the emotional impact on the patient.<b>Results:</b> The study included 100 patients suffering from severe smell loss. Sixty-two patients (62%) were ≥39 years and 38 (38%) were ≤ 40 years old. The mean age of the patients was 37.5 10.8 years. There were 62 females (62%). The mean duration of olfactory loss was 4.4 2.8 months. Sudden onset was reported in 98 patients. Only 2 patients (2%) had rhinorrhea. Eighty-one patients (81%) suffered from mild symptoms of COVID infection. There were 21 smokers (21%). Eighteen patients (18%) had comorbidities. Twenty-seven patients (27%) belonged to the low socioeconomic status. Severe hyposmia (TS of ATT = 4–5) was reported in 96 patients (96%) and anosmia (TS of ATT = 6) in 4 patients (4%). Kessler’s test indicated that 63 patients (63%) experienced moderate to severe distress.<b>Conclusions:</b> The following risk factors showed significant differences in the prognosis of olfactory loss: older age, long duration of loss, smoking, presence of comorbidities, low socioeconomic status, and increased severity of COVID-19. These factors may be important predictors of the persistence of olfactory loss. Factors like sex, onset type, nasal symptoms, severity of olfactory loss, and Kessler’s test score did not show significant differences.

Network pharmacology and experimental validation reveal the mechanisms of sniffing essential oil of Acori Tatarinowii rhizoma in treating olfactory dysfunction

Ethnopharmacological relevanceAcorus tatarinowii Rhizoma, a traditional Chinese medicine known for open the orifices and transform phlegm, is used in the treatment of brain disorders. The essential oil of Acorus tatarinowii Rhizoma (EOAT) has demonstrated neuroprotective properties clinically. However, research into its effect on Olfactory Dysfunction (OD) remains limited. Aim of the studyThis study aimed to investigate the effects and mechanisms of sniffing EOAT on improving olfactory function in a 3-Methylindole (3-MI)-induced OD mouse model. Materials and methodsThe research involved intraperitoneal injection of 3-MI to induce OD in mice. The effects of EOAT treatment were assessed on olfactory function, olfactory bulb (OB) pathology, inflammatory factors, olfactory marker protein (OMP), microglial activation, and related pathway proteins and mRNA. ResultsBased on the GC-MS analysis results of EOAT and network pharmacology studies, we predicted 18 targets associated with the treatment of OD. SLC6A3, MAOB, DRD1, and PTGS2 were identified as the core targets of EOAT against OD. Molecular docking and KEGG enrichment results indicated that EOAT may exert anti-inflammatory effects by acting on the core target PTGS2, with its anti-inflammatory mechanism possibly related to the PI3K/Akt signaling pathway. Subsequent animal experiments confirmed that inhalation of EOAT significantly increased the body weight of OD model mice, shortened the foraging time, enhanced the expression of OMP in OB, reduced damage to the OB cells, and improved olfactory function. Meanwhile, EOAT significantly alleviated the inflammatory response in OB of OD model mice, inhibited the activation of microglial cells, and suppressed the expression of PI3K/Akt signaling pathway proteins and mRNA. ConclusionEOAT inhalation could improve olfactory function in 3-MI-induced OD model. The underlying mechanism may be related to the modulation of the PI3K/Akt signaling pathway.

Factors Associated With Persisting Olfactory Dysfunction After COVID‐19

ABSTRACTBackgroundFortunately, the majority of COVID‐19 patients recover from olfactory dysfunction (OD) within the first couple of weeks. However, from approximately 5% up to 20% continue to suffer from OD even more than 1 year after the onset. Nonetheless, factors associated with long‐lasting OD are hardly known. The aim of this study was to identify favourable and disadvantageous markers of persisting OD in COVID‐19 patients.MethodologySixty‐six patients (46 female; mean age: 39.9 years) that suffer from OD longer than 6 months due to laboratory‐confirmed SARS‐CoV‐2 infection have participated in this longitudinal study. Participants completed comprehensive psychophysical chemosensory tests (i.e., Sniffin' Sticks = TDI) and questionnaires twice at our department—on average 219 ± 80 (T‐1) and 489 ± 89 (T‐2) days after the onset of symptoms, respectively. Olfactory recovery rates were associated with demographic factors and questionnaires using linear regression analysis.ResultsPatients below 40 years of age improved better (TDI: 4.1 ± 4.3 vs. 0.7 ± 5.8; p = 0.008) and achieved statistically significant higher scores (TDI: 31.5 ± 4.0 vs. 27.3 ± 6.7; p = 0.033) regarding psychophysical chemosensory tests. Furthermore, linear regression analysis revealed that parosmia was associated with worse orthonasal smell function (T‐1: β = −0.346, p = 0.004; T‐2: β = −0.384, p = 0.001), especially concerning identification subtest (T‐1: β = −0.395, p = 0.001; T‐2: β = −0.398, p < 0.001). Moreover, increasing parosmia between T‐1and T‐2 led to worse orthonasal olfactory function (β = −0.294, p = 0.016).ConclusionsOlder age and parosmia seem to be unfavourable factors of persisting OD in COVID‐19 patients.

Long-Term Effects of Auricular Medicine – A Key to the Future of Preventive Medicine?

Auricular medicine, based on the concept that the ear reflects the entire body, has gained recognition for treating various conditions through targeted acupuncture. Despite documented short-term benefits, such as pain relief and nervous system regulation, research into its long-term effects is limited. This editorial discusses the need for further long-term studies to explore whether regular auricular acupuncture can offer sustained health benefits and serve a preventive role. It summarizes two studies: one on auricular therapy with magnetic pearls for elderly insomnia and another on frequency-controlled ear acupuncture for COVID-19-related olfactory dysfunction. Both studies suggest potential benefits, underscoring the importance of continued research to fully understand and harness auricular medicine’s preventive and therapeutic potential.

Olfaction and thyroid hormones in patients with subjective cognitive decline, non-amnestic and amnestic mild cognitive impairment.

Thyroid hormones may affect olfaction in different stages of cognitive impairment: subjective cognitive decline (SCD), non-amnestic (naMCI) and amnestic mild cognitive impairment (aMCI). Additionally, biometric parameters, depression, and neuropsychological performance are considered as possible influencing factors. Aretrospective single-center data analysis was conducted during the observation period 2001-2023, with n = 495 (52.3% female) SCD, naMCI and aMCI subjects, aged ≥50years, at the General Hospital of Vienna. The criterion olfactory function was objectively measured by Sniffin' Sticks© odor identification and subjectively through the Assessment of Self-Reported Olfactory Functioning test. Serum thyroid hormone levels, mainly thyroid-stimulating hormone, as well as T3, T4, fT3, and fT4, were used to assess thyroid function. Statistical analyses using IBM SPSS® 29.0.0 covered adjusted multiple linear regression models with hierarchical blocks to predict olfactory performance considering β‑weights. Of the study participants, 4.2% had hypothyroidism and 2.4% had hyperthyroidism. The majority exhibited normal thyroid function. One third (33.5%; 95% confidence interval, CI 29.4-37.0%) were hyposmic. The results indicate no substantial association between thyroid and olfactory functions. Increasing age (β = 0.20), lower performance in the Neuropsychological Test Battery Vienna (NTBV) dimensions verbal memory (β = -0.33) and attention (β = -0.12) appear to be risk factors for lower olfaction. Adiscrepancy between subjective and objective olfaction was found. Thyroid and olfactory functions had no substantial relationship. Higher fT4 correlated weakly with lower odor identification. Increasing age and decreased performance in two out of six NTBV dimensions are relevant prognostic factors for olfactory dysfunction.

Genomic study of taste perception genes in African Americans reveals SNPs linked to Alzheimer’s disease

While previous research has shown the potential links between taste perception pathways and brain-related conditions, the area involving Alzheimer’s disease remains incompletely understood. Taste perception involves neurotransmitter signaling, including serotonin, glutamate, and dopamine. Disruptions in these pathways are implicated in neurodegenerative diseases. The integration of olfactory and taste signals in flavor perception may impact brain health, evident in olfactory dysfunction as an early symptom in neurodegenerative conditions. Shared immune response and inflammatory pathways may contribute to the association between altered taste perception and conditions like neurodegeneration, present in Alzheimer’s disease. This study consists of an exploration of expression-quantitative trait loci (eQTL), utilizing whole-blood transcriptome profiles, of 28 taste perception genes, from a combined cohort of 475 African American subjects. This comprehensive dataset was subsequently intersected with single-nucleotide polymorphisms (SNPs) identified in Genome-Wide Association Studies (GWAS) of Alzheimer’s Disease (AD). Finally, the investigation delved into assessing the association between eQTLs reported in GWAS of AD and the profiles of 741 proteins from the Olink Neurological Panel. The eQTL analysis unveiled 3,547 statistically significant SNP-Gene associations, involving 412 distinct SNPs that spanned all 28 taste genes. In 17 GWAS studies encompassing various traits, a total of 14 SNPs associated with 12 genes were identified, with three SNPs consistently linked to Alzheimer’s disease across four GWAS studies. All three SNPs demonstrated significant associations with the down-regulation of TAS2R41, and two of them were additionally associated with the down-regulation of TAS2R60. In the subsequent pQTL analysis, two of the SNPs linked to TAS2R41 and TAS2R60 genes (rs117771145 and rs10228407) were correlated with the upregulation of two proteins, namely EPHB6 and ADGRB3. Our investigation introduces a new perspective to the understanding of Alzheimer's disease, emphasizing the significance of bitter taste receptor genes in its pathogenesis. These discoveries set the stage for subsequent research to delve into these receptors as promising avenues for both intervention and diagnosis. Nevertheless, the translation of these genetic insights into clinical practice requires a more profound understanding of the implicated pathways and their pertinence to the disease's progression across diverse populations.

Age-related differences in olfactory training outcomes: A prospective cohort study.

While olfactory function decreases with age, it is unknown how age affects olfactory training (OT) efficacy. This study compared OT in two cohorts of subjects: aged ≤50 (younger cohort) and aged 51+ (older cohort) with olfactory dysfunction (OD) primarily from COVID-19 infection. Subjects with OD primarily secondary to COVID-19 infection were prospectively recruited and enrolled into an OT registry. Baseline data were collected and they were provided with a training kit and asked to complete OT at home twice daily for 6 months. Participants were asked to follow-up at 3 and 6 months during training for olfactory testing and quality-of-life surveys (Sino-Nasal Outcomes Test-22 [SNOT-22] and Questionnaire of Olfactory Disorders Negative Statements [QoD-NS]). Fifty-six participants completed OT (younger cohort: n=26, older cohort: n=30). There were no significant differences between cohorts' Affordable Rapid Olfactory Measurement Array (AROMA), QoD-NS, or SNOT-22 scores at any time point. Both cohorts showed significant AROMA score improvement of more than 16 points from baseline to 3 months (younger cohort: p=0.001; older cohort: p=0.008). The younger cohort had significant improvements in QoD-NS (p=0.008) and SNOT-22 (p=0.042) between baseline and 3 months while the older cohort improved from 3 to 6 months (QoD-NS: p=0.027, SNOT-22: p=0.049). Both cohorts demonstrated similar significant improvement in olfactory function after 3 months of OT. The timeline of subjective improvement was different between cohorts, with younger patients experiencing earlier improvement.

Dual blockade of IL-4 and IL-13 with dupilumab ameliorates sensorineural olfactory dysfunction in mice with eosinophilic sinonasal inflammation.

Dupilumab, an antibody that binds IL-4Rα and inhibits IL-4 and IL-13 signals, has demonstrated efficacy in chronic rhinosinusitis with nasal polyps (CRSwNP) primarily characterized by type 2 inflammation. Current evidence suggests that the rate of improvement in olfactory dysfunction with dupilumab exceeds that of nasal polyp reduction, yet the underlying mechanism remains undisclosed. We hypothesize that dupilumab may initially ameliorate sensorineural olfactory dysfunction. Male BALB/c mice were intranasally administered ovalbumin and Aspergillus protease for 12 weeks to induce eosinophilic sinonasal inflammation. Dupilumab treatment was also administered. The mice underwent histological assessment, olfactory behavioural test, and gene expression profiling to identify neuroinflammatory markers within the olfactory bulb. Dupilumab treatment resulted in a reduction in the number of mucosal protruding lesions, as well as decreased infiltration of eosinophils and neutrophils, along with a decrease in olfactory sensory neuron injury. Furthermore, there was a downregulation in the mRNA expression related to microglia activation and neuroinflammation in the olfactory bulb. Dupilumab improves the sensorineural pattern of olfactory dysfunction in mice, potentially explaining why olfaction improves more rapidly than polyp reduction in patients with CRSwNP.

In Response to Impact of Nutritional Status on COVID-19-Induced Olfactory Dysfunction.

In Response to Impact of Nutritional Status on COVID-19-Induced Olfactory Dysfunction.

Early detection of Alzheimer's disease using the MEMORIES mnemonic

AbstractThe rising incidence and death rates linked to Alzheimer's disease (AD) highlight an urgent issue. Genetic screening is celebrated as a significant advancement for its early detection capabilities, pinpointing those at risk before the emergence of symptoms. Yet, the limited availability of these technologies highlights a critical gap in widespread application. This review pivots to the potential of presymptomatic clinical assessments as a readily available, economical, and simple strategy for early detection. Traditionally, AD diagnosis relies on the late‐stage identification of cognitive deterioration, functional impairments, and neuropsychiatric symptoms, coinciding with advanced brain degeneration. Conversely, emerging research identifies early indicators preceding significant degeneration, manifesting years before clinical symptoms. We introduce a mnemonic, MEMORIES, to categorize these prodromal: Metabolism changes, Eye/visual impairments, March (refer to gait disturbances), Olfactory dysfunction, Rhythm (blood pressure and heart rate), Insensitivity of the tongue, Ears (hearing loss), and Stool alterations. Recognizing these prodromal through clinical examinations provides a valuable strategy for initiating preventative actions against brain degeneration. This approach advocates for broadening the screening lens beyond genetic screening to encompass clinical evaluations, enhancing early detection and intervention opportunities for AD.

Olfactory event-related potentials (OERPs) and trigeminal event-related potentials (TERPs) in subjects after Covid-19 infection: single-center prospective study.

Olfactory dysfunction (OD) is a common symptom associated with Covid-19. During the Covid-19 pandemic, the importance of psychophysical olfactory tests and electrophysiological olfactory assessment increased. The purpose of the study was to analyze the psychophysical olfactory tests and the post-covid curves of olfactory event-related potentials (OERPs) and trigeminal event-related potentials (TERPs). The prospective study included 98 subjects (62 females / 36 males). The average age was 42 years (range 21-84 years). Group I (n = 77) contained participants who had been infected with Covid-19. They were enrolled in the study at least 1 year after Covid-19. Group II (n = 21) was the healthy normosmic control group. In Group I, the OERPs of 18% participants were absent. Patients in Group I were statistically more likely to have an absence of OERPs (p = 0.036) than subjects in Group II. We did not detect a statistical difference in amplitudes and latencies of the OERPs between Group I and Group II. In Group I, N1 latency of the TERPs was significantly longer (p = 0.002) than in Group II. The amplitude of the N1-P2 interval of the TERPs was significantly lower (p = 0.025) in Group I than in Group II. According to the psychophysical Sniffin stick identification test, hyposmia was detected in 39% in Group I versus 0% in the control Group II. OD is a common post-covid symptom. The presence of OERPs is a significant prognostic factor for olfactory function after Covid 19. We detected a lower percentage of absence of OERPs after Covid-19 compared to the previously published studies of post-viral OD and post-infectious OD. For TERPs, we detected a longer N1 latency and a lower amplitude for the N1-P2 interval after Covid-19. OERPs and TERPs can be considered valid biomarkers to evaluate the progress of post-covid OD.

Brain perfusion alterations in patients and survivors of COVID‐19 infection using arterial spin labeling: A systematic review

AbstractCoronavirus disease (COVID‐19) has been shown to impact the central nervous system, leading to various neurological complications. Arterial spin labeling (ASL), a non‐invasive magnetic resonance imaging technique, enables the measurement of cerebral blood flow and perfusion abnormalities. This systematic review aims to synthesize ASL findings in patients with COVID‐19 and assess the potential role of ASL in diagnosing and managing neurological complications. A comprehensive search was conducted on PubMed and Scopus for studies related to ASL in individuals with COVID‐19 or post‐COVID‐19 syndrome published between December 2019 and August 2024. Extracted data encompassed study characteristics, ASL protocols, cognitive assessments, and principal findings. The most consistent observation across studies was hypoperfusion detected in various brain regions, particularly within the frontal lobes, which may correlate with cognitive impairment and olfactory dysfunction. Additionally, some investigations reported hyperperfusion localized to the leptomeninges. These results may reflect underlying mechanisms such as hypoxic–ischemic injury, inflammation, vascular dysfunction, and neuronal damage attributable to COVID‐19. In conclusion, ASL has emerged as a valuable tool for evaluating brain perfusion among patients affected by or recovering from COVID‐19 since it offers critical insights into cerebral hemodynamics and metabolism. Further research is warranted to validate these ASL findings and elucidate whether post‐COVID‐19 syndrome contributes to persistent brain perfusion issues.

Systems Thinking, Causal Loop Diagram, and Systems Dynamic in Public Health Challenges: Navigating Long COVID Syndrome and Sense of Smell in LGBTQIA+ Communities

ABSTRACTBackgroundThe coronavirus pandemic has profoundly affected global health, economic stability, and environmental sustainability. Despite these challenges, significant gaps in data remain, particularly in effectively assessing and engaging diverse communities such as color, LGBTQIA+ individuals, and low‐income groups. This shortage of comprehensive research limits our capacity to undertake sensitive studies, specifically in dealing with the complexities of long COVID, which some individuals continue to suffer from after their initial recovery.ObjectiveThis review delves into the ongoing repercussions of long‐term COVID‐19, a postinfectious syndrome marked by neurological symptoms such as cognitive deficits and sensory impairments, which may last well beyond the acute phase of the illness. These symptoms frequently overlap with mental health issues (e.g., anxiety and depression), which can aggravate the socioeconomic challenges faced by vulnerable populations, especially within the LGBTQA+ communities.MethodsTo tackle these complex interactions, we have introduced a novel public health framework: model‐based systems thinking (MBST), which incorporates System Dynamics and causal loop diagrams (CLD).Results and DiscussionThe articles were selected on the basis of their discussion of COVID‐19‐associated anosmia, exploration of olfactory dysfunction alongside neurocognitive disorders, and the challenges experienced in LGBQA+ communities. This approach offers a robust framework for dissecting the intricate ties between socioeconomic factors, health outcomes, and the extended recovery trajectories associated with long‐term COVID‐19, with a particular focus on olfactory dysfunction. We also explore strategies to make our models more accessible to healthcare providers and the LGBTQA+ communities, encouraging its broader adoption.ConclusionLong COVID's impact on public health and marginalized communities highlights the urgent need for adopting systems thinking models. Additionally, this article calls for a concerted effort from all experts to foster multidisciplinary, team‐based research and implement effective support measures for COVID‐19 survivors across all communities, mainly focusing on the scientific, social, and behavioral challenges LGBTQIA+ and low‐income individuals face.

Parosmia in patients with post-infectious olfactory dysfunction in the era of COVID-19-associated olfactory impairment.

Alarge number of patients with olfactory impairment are affected by parosmia or phantosmia. This study aimed to examine the demographic and clinical characteristics of parosmia. We performed aretrospective data analysis of patients consulting at our Smell and Taste Outpatient Clinic. Atotal of 297 patients were included (203 women, mean age44.4 ± 13.7years). Olfactory function was quantified using the "Sniffin' Sticks" composite TDI (odor threshold, determination, and identification) score. The presence of qualitative olfactory impairment was assessed trough medical history and aparosmia questionnaire. Most of the patients showed olfactory impairment after an infection with SARS-CoV‑2 (84%) and were diagnosed with parosmia (49%). Patients with parosmia (PAR) (n = 201) were significantly younger compared to the group without parosmia (noPAR; n = 92) (PAR 43.2 ± 13years vs. noPAR 47 ± 15.1 years, p = 0.03) and had aslightly shorter duration of disease, without reaching statistical significance (PAR 10.3 ± 4.9months, noPAR 13.6 ± 37.6 months, p = 0.23). They also had higher TDI scores (PAR 24.3 ± 7points, noPAR 21.4 ± 8.2points, p = 0.003). Patients affected by parosmia were younger and had abetter olfactory function compared to patients without parosmia.

Resistance to high-fat diet-induced weight gain in transgenic mice overexpressing human wild-type α-synuclein: A model for metabolic dysfunction in Parkinson's disease.

Unintentional weight loss, primarily due to the loss of fat mass rather than muscle mass, is common among patients with Parkinson's disease (PD) and is associated with poor quality of life and accelerated disease progression. Since transgenic mice overexpressing human wild-type α-synuclein (α-Syn mice) are modestly leaner than control mice, and since diabetes, a metabolic disorder, is a major risk factor for PD, we reasoned that high-fat diet-induced diabetes/metabolic dysregulation in α-Syn mice may serve as a robust tool for exploring how early α-synuclein pathology contributes to metabolic dysregulation, leading to weight loss in PD. Thus, α-Syn and age-matched controls were fed a high-fat diet (HFD) chow (60% fat calories) ad libitum for four months. Compared with controls on HFD (control-HFD), α-Syn mice on HFD (α-Syn-HFD) were dramatically leaner. The resistance to gaining weight in α-Syn-HFD mice was accompanied by improved glucose tolerance, a dramatic decrease in fat mass, and an increase in energy expenditure. Despite this leaner phenotype and better glucose tolerance, the mortality was much higher in male α-Syn-HFD mice than in all controls, but was unaffected in females, suggesting protective effects of female sex hormones, as well as lower α-synuclein levels. Immunoblot analysis of insulin signaling in the olfactory bulb, the proposed initial seeding site of α-synuclein pathology, revealed a decrease of IGF-IRβ, p GSK, and p mTOR in α-Syn-HFD mice. Since GSK-3β and mTOR regulate synaptic plasticity, we assessed levels of PSD-95 and synaptophysin in the olfactory bulb. As anticipated, we observed a significant decrease in the levels of PSD-95, along with a potentially compensatory increase in synaptophysin levels. Our results show that α-Syn mice, when challenged with diet-induced diabetes/metabolic dysregulation, clearly reveal a profile of robust metabolic dysfunction, thus providing a sensitive tool for assessing the underlying mechanism of metabolic dysfunction and its impact on weight loss and disease progression in PD. We propose a role for olfactory dysfunction in PD-related unintentional weight loss and suggest that strategies aimed at increasing body weight/BMI will improve the quality of life and prognosis for people living with PD.

Pathological Findings of Post-Viral Olfactory Dysfunction: A Systematic Review

Pathological Findings of Post-Viral Olfactory Dysfunction: A Systematic Review

Authors' Reply: The Role of Malnutrition and Psychiatric Illnesses in Olfactory Dysfunction Post-Kidney Transplantation.

Authors' Reply: The Role of Malnutrition and Psychiatric Illnesses in Olfactory Dysfunction Post-Kidney Transplantation.