Olfactory dysfunction in COVID-19: pathology and long-term implications for brain health

Doty, Richard L.

doi:10.1016/j.molmed.2022.06.005

Cited by 62 publications

(54 citation statements)

References 134 publications

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“…The prevalence of ageusia in our study is also similar to other meta-analyses (11.7% versus 10%). A novel finding in this review was the prevalence of hyposmia and hypogeusia, both of which were much higher than anosmia and (36)(37)(38), with some authors recommending specific olfactory theory to improve long-term olfactory function (36). Other authors also suggest a genetic component, indicating that the locus of genes UGT2A1 and UGT2A2 may be a casual factor of anosmia (39).…”

Section: Discussionmentioning

confidence: 82%

“…A review by Ahmed et al ( 35 ) suggested five possible mechanisms behind anosmia in the acute phase of COVID-19, including the affection of the ACE-2 receptors, damage of supporting cells of the olfactory epithelium, affection of the frontal lobe, inflammatory obstruction of olfactory clefts, and zinc deficiency. In particular, several studies have reported long term damage of the olfactory epithelium in COVID-19 patients ( 36 – 38 ), with some authors recommending specific olfactory theory to improve long-term olfactory function ( 36 ). Other authors also suggest a genetic component, indicating that the locus of genes UGT2A1 and UGT2A2 may be a casual factor of anosmia ( 39 ).…”

Section: Discussionmentioning

confidence: 99%

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The prevalence of sensory changes in post-COVID syndrome: A systematic review and meta-analysis

2022

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Post-COVID syndrome can be defined as symptoms of COVID-19 that persist for longer than 12 weeks, with several studies reporting persistent symptoms relating to the sensory organs (eyes, ears, and nose). The aim of this systematic review was to examine the prevalence of persistent anosmia, hyposmia, ageusia, and hypogeusia, as well as eye/vision and ear/hearing related long-COVID symptoms. Authors searched the electronic databases from inception to November 2021. Search terms included words related to long-COVID, smell, taste, eyes/vision, and ears/hearing, with all observational study designs being included. A random effects meta-analysis was undertaken, calculating the prevalence proportions of anosmia, hyposmia, ageusia, and hypogeusia, respectively. From the initial pool, 21 studies met the inclusion criteria (total n 4,707; median n per study 125; median age = 49.8; median percentage female = 59.2%) and 14 were included in the meta-analysis The prevalence of anosmia was 12.2% (95% CI 7.7–16.6%), hyposmia 29.9% (95% CI 19.9–40%), ageusia 11.7% (95% CI 6.1–17.3%), and hypogeusia 31.2% (95% 16.4–46.1%). Several eye/vision and ear/hearing symptoms were also reported. Considering that changes in the sensory organs are associated with decreases in quality of life, future research should examine the etiology behind the persistent symptoms.Systematic review registration[www.crd.york.ac.uk/prospero], identifier [CRD42021292804].

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

The prevalence of sensory changes in post-COVID syndrome: A systematic review and meta-analysis

2022

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“…One autopsy study in two patients found that there was inflammatory olfactory neuropathy, mainly axonal damage in olfactory epithelium in two patients with COVID-19 ( 31 ), whereas, the olfactory tracts were largely unremarkable. Significant pathology in central nervous system structures, including those related to olfaction, appears to be relatively rare ( 32 ). Based on these results, we infer that local inflammation in nasal mucosa rather than the systemic inflammation may contribute to COVID-19 related hyposmia in the acute stage ( 33 ).…”

Section: Discussionmentioning

confidence: 99%

Clinical characteristics and short-term recovery of hyposmia in hospitalized non-severe COVID-19 patients with Omicron variant in Shanghai, China

Shen

Wang

et al. 2022

Front. Med.

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BackgroundOlfactory dysfunction is a common neurological symptom of Corona Virus Disease 2019(COVID-19). Little is known about hyposmia after COVID-19 infection with Omicron variant in Chinese population.ObjectiveTo investigate the incidence, clinical characteristics and recovery of hyposmia in hospitalized non-severe COVID-19 patients with Omicron variant in Shanghai, China.MethodsThree hundred and forty-nine Chinese non-severe COVID-19 patients with Omicron variant were consecutively enrolled in a designated hospital to investigate the incidence of hyposmia in hospitalization and the recovery rate 1 month later. The visual assessment scale (VAS) was used to evaluate the severity of hyposmia. We compared the demographic, clinical features and treatment outcomes, as well as laboratory parameters between patients with and without hyposmia.ResultsThe cross-sectional survey showed that 22 (6.3%) hospitalized patients with non-severe COVID-19 had hyposmia. Patients with hyposmia were younger (61.5 vs. 72.0, p = 0.002), had more related clinical symptoms (sore throat, cough, poor appetite, diarrhea, myalgia and taste impairment, etc.), a higher proportion of moderate clinical type (31.8 vs. 13.5%, p = 0.028) and longer duration of hospitalization (11 vs. 8 days, p = 0.027) than those without hyposmia. Whereas, there were no significant differences regarding gender, comorbidity and nucleic acid conversion time between the two groups. Laboratory subgroup analyses demonstrated that patients with hyposmia had slightly low serum IL-6 and TNF-α levels. However, both of the levels were not associated with hyposmia occurrence in multivariate regression analyses. Further follow-up study disclosed that 16 of 22 (72.7%) hyposmia patients had recovered olfaction 1 month later. Serum IL-6 and TNF-α levels were similar between hyposmia recovered patients and those with persistent hyposmia.ConclusionAlthough the incidence of hyposmia after Omicron variant infection is relatively low and the short-term recovery rate is quite high, patients with hyposmia are prone to have a higher proportion of both upper and lower respiratory tract involvements, gastrointestinal and neurological symptoms, contributing to a longer duration of hospitalization.

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“…In most cases, olfaction recovers within weeks from the infection. However, in 20% of cases, patients can develop a persistent form of olfactory dysfunction (OD), lasting more than six months (or years) after the resolution of COVID-19 ( Butowt and von Bartheld, 2021 , Doty, 2022 , Esposito et al, 2022 , Tan et al, 2022 ).…”

Section: Introductionmentioning

confidence: 99%

Substance P and Prokineticin-2 are overexpressed in olfactory neurons and play differential roles in persons with persistent post-COVID-19 olfactory dysfunction

Schirinzi¹,

Lattanzi²,

Maftei³

et al. 2023

Brain, Behavior, and Immunity

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Olfactory dysfunction in COVID-19: pathology and long-term implications for brain health

Cited by 62 publications

References 134 publications

The prevalence of sensory changes in post-COVID syndrome: A systematic review and meta-analysis

The prevalence of sensory changes in post-COVID syndrome: A systematic review and meta-analysis

Clinical characteristics and short-term recovery of hyposmia in hospitalized non-severe COVID-19 patients with Omicron variant in Shanghai, China

Substance P and Prokineticin-2 are overexpressed in olfactory neurons and play differential roles in persons with persistent post-COVID-19 olfactory dysfunction

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