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Olfactory recovery following infection with COVID-19: A systematic review

ABSTRACT: Olfactory loss has been identified as one of the common symptoms related to COVID-19 infection. Although olfactory loss is recognized, our understanding of both the extent of loss and time to olfactory recovery following infection is less well known. Similarly, knowledge of potential impactful patient factors and therapies that influence olfactory recovery is desirable but is not overtly clear in the literature. Our systematic review sought to fill this knowledge gap. We included studies that: involved either an observational or an interventional design that reported data on patients with olfactory dysfunction due to Reverse Transcription Polymerase Chain Reaction (RT-PCR) diagnosed COVID-19 infection; and reported data regarding olfactory recovery measured by an objective olfactory test, Likert scale and/or visual analog scale (VAS). The study methods were determined a priori and registered in PROSPERO (Registration Number CRD42020204354). An information specialist searched Medline, Embase, LitCovid and the Cochrane Register of Controlled Trials up to March 2021, and two reviewers were involved in all aspects of study selection and data collection. After screening 2788 citations, a total of 44 studies of assorted observational designs were included. Patients had undergone objective COVID-19 testing, and most were adult patients with mild to moderate COVID-19. Olfactory recovery was found to occur as early as 7 days, with most patients recovering olfaction within 30 days. Few studies included prolonged follow-up to 6 months or longer duration. Poor olfaction at initial presentation was associated with poor recovery rates. Only a small number of studies assessed olfactory retraining and steroid therapy. Additional trials are underway.

SUBMITTER: Jafar A

PROVIDER: S-EPMC8577770 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundOlfactory impairments and anosmia from COVID-19 infection typically resolve within 2-4 weeks, although in some cases, symptoms persist longer. COVID-19-related anosmia is associated with olfactory bulb atrophy, however, the impact on cortical structures is relatively unknown, particularly in those with long-term symptoms.MethodsIn this exploratory, observational study, we studied individuals who experienced COVID-19-related anosmia, with or without recovered sense of smell, and compared against individuals with no prior COVID-19 infection (confirmed by antibody testing, all vaccine naïve). MRI Imaging was carried out between the 15th July and 17th November 2020 at the Queen Square House Clinical Scanning Facility, UCL, United Kingdom. Using functional magnetic resonance imaging (fMRI) and structural imaging, we assessed differences in functional connectivity (FC) between olfactory regions, whole brain grey matter (GM) cerebral blood flow (CBF) and GM density.FindingsIndividuals with anosmia showed increased FC between the left orbitofrontal cortex (OFC), visual association cortex and cerebellum and FC reductions between the right OFC and dorsal anterior cingulate cortex compared to those with no prior COVID-19 infection (p < 0.05, from whole brain statistical parametric map analysis). Individuals with anosmia also showed greater CBF in the left insula, hippocampus and ventral posterior cingulate when compared to those with resolved anosmia (p < 0.05, from whole brain statistical parametric map analysis).InterpretationThis work describes, for the first time to our knowledge, functional differences within olfactory areas and regions involved in sensory processing and cognitive functioning. This work identifies key areas for further research and potential target sites for therapeutic strategies.FundingThis study was funded by the National Institute for Health and Care Research and supported by the Queen Square Scanner business case.

Project description:ImportancePrevalence of post-viral olfactory loss has increased dramatically due to the frequency and severity of olfactory dysfunction associated with infection by the SARS-CoV-2 virus.ObjectiveTo determine the trajectory of COVID-19 olfactory loss over a six-month period. A key secondary objective is to assess predictive factors associated with the recovery of olfaction.DesignLongitudinal repeated-measures study that enrolled from May 5, 2020 to February 2, 2021, with the last date of data collection on June 15, 2021.SettingBarnes-Jewish HealthCare/Washington University School of Medicine facilities (Saint Louis, Missouri, USA).ParticipantsIndividuals who tested positive for SARS-CoV-2 by real-time polymerase chain reaction on nasopharyngeal swab and indicated olfactory loss on COVID-19 screening questionnaire. Individuals were excluded if they had previously diagnosed history of olfactory loss, neurodegenerative disorders, <18 years of age, admitted to hospital service, unable to read, write, and understand English, or lacked computer or internet access.Interventions/exposuresWatch and wait for spontaneous recovery.Main outcome(s) and measure(s)Participants completed olfactory assessments every 30 days for six months. Each assessment consisted of the University of Pennsylvania Smell Identification Test (UPSIT), an objective "scratch-and-sniff" test, and Clinical Global Impressions (CGI), a subjective Likert rating scale.ResultsThe mean age was 41 years old (SD = 16). 39 (80 %) were female and 42 (86 %) white. At baseline assessment of objective olfaction, 18 (36 %) participants had anosmia or severe hyposmia. Subjective, complete recovery at six months was 81 % (95 % CI 74 % to 88 %). Likelihood of recovery was associated with age <50 years (aHR = 8.1 (95 % CI 1.1 to 64.1)) and mild olfactory loss at baseline (UPSIT = 30-33 for males and 31-34 for females) (aHR 6.2 (95 % CI 1.2 to 33.0)).Conclusions and relevanceThe trajectory of olfactory recovery among adults with COVID-19 olfactory loss illustrated rapid recovery within 2-3 weeks of infection, and by six months 81 % had recovered based on self-report. Age <50 years old and mild severity of olfactory loss at baseline were associated with increased likelihood of recovery of olfaction. These findings can be used to inform shared decision-making with patients.

Project description:ObjectivesTo establish the evidence for rehabilitation interventions tested in populations of patients admitted to ICU and critical care with severe respiratory illness, and consider whether the evidence is generalizable to patients with COVID-19.MethodsThe authors undertook a rapid systematic review. Medline (via OvidSP), CINAHL Complete (via EBSCOhost), Cochrane Library, Cochrane Database of Systematic Reviews and CENTRAL (via Wiley), Epistemonikos (via Epistemonikos.org), PEDro (via pedro.org.au) and OTseeker (via otseeker.com) searched to 7 May 2020. The authors included systematic reviews, RCTs and qualitative studies involving adults with respiratory illness requiring intensive care who received rehabilitation to enhance or restore resulting physical impairments or function. Data were extracted by one author and checked by a second. TIDier was used to guide intervention descriptions. Study quality was assessed using Critical Skills Appraisal Programme (CASP) tools.ResultsSix thousand nine hundred and three titles and abstracts were screened; 24 systematic reviews, 11 RCTs and eight qualitative studies were included. Progressive exercise programmes, early mobilisation and multicomponent interventions delivered in ICU can improve functional independence. Nutritional supplementation in addition to rehabilitation in post-ICU hospital settings may improve performance of activities of daily living. The evidence for rehabilitation after discharge from hospital following an ICU admission is inconclusive. Those receiving rehabilitation valued it, engendering hope and confidence.ConclusionsExercise, early mobilisation and multicomponent programmes may improve recovery following ICU admission for severe respiratory illness that could be generalizable to those with COVID-19. Rehabilitation interventions can bring hope and confidence to individuals but there is a need for an individualised approach and the use of behaviour change strategies. Further research is needed in post-ICU settings and with those who have COVID-19. Registration: Open Science Framework https://osf.io/prc2y.

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Olfactory recovery following infection with COVID-19: A systematic review

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