ArticleBrain sciences2022
Olfactory Dysfunction, Headache, and Mental Clouding in Adults with Long-COVID-19: What Is the Link between Cognition and Olfaction? A Cross-Sectional Study.
Article in Brain sciences, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 37 papers, 2 of them syntheses that pooled it.
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Who cites it
37 citing papers in PubMed, 2 syntheses or guidelines pooled it, 55 citations in OpenAlex.
- [Cognition and Long COVID: A PRISMA Systematic Review of Longitudinal Studies].Revista de neurologia · 2025Pooled it
- The assessment of qualitative olfactory dysfunction in COVID-19 patients: a systematic review of tools and their content validity.Frontiers in psychology · 2023Pooled it
- Persistent COVID-19 parosmia and olfactory loss post olfactory training: randomized clinical trial comparing central and peripheral-acting therapeutics.European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery · 2024Trial
- Treatment of COVID-19 olfactory dysfunction with olfactory training, palmitoylethanolamide with luteolin, or combined therapy: a blinded controlled multicenter randomized trial.European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery · 2023Trial
- Trial
- Neurological Manifestations of Long COVID: Current Evidence, Emerging Concepts, and Future Perspectives.Journal of clinical medicine · 2026Review
- Comparisons between anosmia and ageusia with neurological symptoms and cardiorespiratory fitness among post-COVID-19 individuals: a cross-sectional study.Acta neurologica Belgica · 2026Article
- Review
- Functional olfactory impairment and fatigue in post-COVID-19 syndrome including ME/CFS - a longitudinal prospective observational study.Brain, behavior, & immunity - health · 2025Article
- Olfactory Dysfunction and Cognitive Decline: Are They Related?Current allergy and asthma reports · 2025Review
- Sense of Smell in Individuals with Fibromyalgia: a Tractography Study.Clinical neuroradiology · 2025Article
- The Adaptive Role of Entorhinal Cortical Thickness in Post-COVID 19 Cognitive Impairment.Noro psikiyatri arsivi · 2025Article
- Neurological, psychological, psychosocial complications of long-COVID and their management.Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology · 2025Review
- Animal models of Long Covid: A hit-and-run disease.Science translational medicine · 2024Review
- Long Neuro-COVID-19: Current Mechanistic Views and Therapeutic Perspectives.Biomolecules · 2024Review
- Olfactory dysfunction as an early predictor for post-COVID condition at 1-year follow-up.Brain and behavior · 2024Article
- Brain temperature and free water increases after mild COVID-19 infection.Scientific reports · 2024Article
- A Comprehensive Review of COVID-19-Related Olfactory Deficiency: Unraveling Associations with Neurocognitive Disorders and Magnetic Resonance Imaging Findings.Diagnostics (Basel, Switzerland) · 2024Review
- Understanding the olfactory role in post-COVID cognitive and neuropsychiatric manifestations.Frontiers in psychology · 2024Article
- A murine model of post-acute neurological sequelae following SARS-CoV-2 variant infection.Frontiers in immunology · 2024Article
Corrections and comments
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Authors and funding
12 authors at 7 institutions in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Smell alteration and cognitive impairment are common features of the Long-COVID Syndrome. Mental clouding, often described as brain fog, might affect smell by altering recollection of odors or through a share mechanism of neuroinflammation. We investigated mental clouding, headache, and cognitive function in adult patients with persistent COVID-19 olfactory dysfunction. This multi-center cross-sectional study enrolled 152 adults with self-reported olfactory dysfunction from 3 tertiary centers specialized in COVID-19 olfactory disorders. Inclusion criteria were smell alterations after COVID-19 persisting over 6 months from infection, age >18 and < 65. Exclusion criteria included smell alterations, headache, or memory problems prior to COVID-19 infection. The patients were evaluated by olfactometry, nasal endoscopy, headache scale, cognitive assessment, Mini Mental State Examination (MMSE), and self-reported measures. Smell dysfunction was stratified and classified based on olfactory deficit severity and presence of olfactory distortion (parosmia, cacosmia). Data on smell disorder, mental clouding, MMSE, and headache were analyzed to assess correlations. Among the 152 patients studied, 50 (32.8%) presented with anosmia, 25 (16.4%) with hyposmia, 10 (6.6%) with parosmia/cacosmia, and 58 patients (38.2%) with a combination of hyposmia and parosmia; seven (4.6%) patients suffered from headache exclusively, and two (1.4%) had headache and mental clouding as their primary symptom. Headache was reported by 76 (50%) patients, and mental clouding by 71 (46.7%). The patients reporting headache, mental clouding, or both, had significantly increased risk of suffering from anosmia and/or hyposmia when compared with their counterparts without these neurological symptoms. No patients had reduced MMSE scores. In our cohort of adult patients with post-COVID-19, smell alterations persisting over 6 months, cognitive impairment and headache were associated with more severe olfactory loss, consistent with neuroinflammatory mechanisms mediating a variety of Long-COVID symptoms.
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