Tag: long Covid

Sequelae in Adults at 6 Months After COVID-19 Infection

Abstract:

Introduction: Many individuals experience persistent symptoms and a decline in health-related quality of life (HRQoL) after coronavirus disease 2019 (COVID-19) illness.1 Existing studies have focused on hospitalized individuals 30 to 90 days after illness onset2-4 and have reported symptoms up to 110 days after illness.3 Longer-term sequelae in outpatients have not been well characterized.

Methods: A longitudinal prospective cohort of adults with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was enrolled at the University of Washington with a concurrent cohort of healthy patients in a control group (eAppendix in the Supplement). Electronic informed consent was obtained, and the study was approved by the University of Washington human participants institutional review board. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. COVID-19 symptom data were obtained at the time of acute illness or retrospectively recounted at a 30-day enrollment visit. A total of 234 participants with COVID-19 were contacted between August and November 2020 to complete a single follow-up questionnaire between 3 and 9 months after illness onset. We did not perform statistical tests for this descriptive analysis because of the small numbers in each subgroup. Data analysis was conducted in R version 4.0.2 (R Project for Statistical Computing).

Results: A total of 177 of 234 participants (75.6%; mean [range] age, 48.0 [18-94] years; 101 [57.1%] women) with COVID-19 completed the survey. Overall, 11 (6.2%) were asymptomatic, 150 (84.7%) were outpatients with mild illness, and 16 (9.0%) had moderate or severe disease requiring hospitalization (Table). Hypertension was the most common comorbidity (23 [13.0%]). The follow-up survey was completed a median (range) of 169 (31-300) days after illness onset among participants with COVID-19 (Figure, A) and 87 (71-144) days after enrollment among 21 patients in the control group. Among participants with COVID-19, persistent symptoms were reported by 17 of 64 patients (26.6%) aged 18 to 39 years, 25 of 83 patients (30.1%) aged 40 to 64 years, and 13 of 30 patients (43.3%) aged 65 years and older. Overall, 49 of 150 outpatients (32.7%), 5 of 16 hospitalized patients (31.3%), and 1 of 21 healthy participants (4.8%) in the control group reported at least 1 persistent symptom. Of 31 patients with hypertension or diabetes, 11 (35.5%) experienced ongoing symptoms.

The most common persistent symptoms were fatigue (24 of 177 patients [13.6%]) and loss of sense of smell or taste (24 patients [13.6%]) (Figure, B). Overall, 23 patients (13.0%) reported other symptoms, including brain fog (4 [2.3%]). A total of 51 outpatients and hospitalized patients (30.7%) reported worse HRQoL compared with baseline vs 4 healthy participants and asymptomatic patients (12.5%); 14 patients (7.9%) reported negative impacts on at least 1 activity of daily living (ADL), the most common being household chores.

Discussion: In this cohort of individuals with COVID-19 who were followed up for as long as 9 months after illness, approximately 30% reported persistent symptoms. A unique aspect of our cohort is the high proportion of outpatients with mild disease. Persistent symptoms were reported by one-third of outpatients in our study, consistent with a previously reported study,4 in which 36% of outpatients had not returned to baseline health by 14 to 21 days following infection. However, this has not been previously described 9 months after infection.

Consistent with existing literature, fatigue was the most commonly reported symptom.2-4 This occurred in 14% of individuals in this study, lower than the 53% to 71%2-4 reported in cohorts of hospitalized patients, likely reflecting the lower acuity of illness in our cohort. Furthermore, impairment in HRQoL has previously been reported among hospitalized patients who have recovered from COVID-19; we found 29% of outpatients reported worsened HRQoL.5

Notably, 14 participants, including 9 nonhospitalized individuals, reported negative impacts on ADLs after infection. With 57.8 million cases worldwide, even a small incidence of long-term debility could have enormous health and economic consequences.6

Study limitations include a small sample size, single study location, potential bias from self-reported symptoms during illness episode, and loss to follow-up of 57 participants. To our knowledge, this study presents the longest follow-up symptom assessment after COVID-19 infection. Our research indicates that the health consequences of COVID-19 extend far beyond acute infection, even among those who experience mild illness. Comprehensive long-term investigation will be necessary to fully understand the impact of this evolving viral pathogen.

Source: Jennifer K. Logue, BS; Nicholas M. Franko, BS; Denise J. McCulloch, MD, MPH; et al Dylan McDonald, BA; Ariana Magedson, BS; Caitlin R. Wolf, BS; Helen Y. Chu, MD, MPH. Sequelae in Adults at 6 Months After COVID-19 Infection. JAMA Netw Open. 2021;4(2):e210830. doi:10.1001/jamanetworkopen.2021.0830 https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2776560

Long COVID Advocates Join Together To Form Alliance To Make Policy Recommendations, Secure Research Funding, And Transform Understanding Of Post-Viral Illnesses

Press Release:

LOS ANGELES, Feb. 25, 2021 /PRNewswire/ — Today, leaders of 50 organizations and patient groups announced the formation of the Long COVID Alliance. The Alliance includes a network of patient-advocates, scientists, public health and disease experts, and drug developers who have joined together to leverage their collective knowledge and resources to educate policymakers and accelerate research that will address the challenges faced by ‘COVID long haulers’ and related post-viral illnesses.

Their goal is to transform the current understanding of Long COVID and related post-infectious illnesses such as:  myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), postural orthostatic tachycardia syndrome (POTS), other forms of dysautonomia, Ehlers-Danlos syndrome (EDS), hypermobility spectrum disorder (HSD) and mast cell activation syndrome (MCAS), autoimmune diseases and other related illnesses.

“The Long COVID Alliance is a critical collaboration based on the current reality that doctors and researchers are reporting that millions of COVID-19 patients continue to experience chronic and often debilitating post-viral symptoms. This state of extended illness is presently labeled Long COVID,” said Oved Amitay, Solve M.E. President and Chief Executive Officer, one of the three Alliance founders. “Even though tests might reveal that no virus remains in the body, COVID-19 ‘long haulers’ continue to struggle, often alone. Our community brings past experiences that are relevant to the current crisis.”

In 2020, this same group came together to successfully call for urgent government investments for Long COVID, and $1.15 billion for long-term COVID-19 research at the National Institutes of Health shortly followed. The effort laid the foundation for the new Long COVID Alliance, which will prioritize:

  • Health equity and confronting systemic bias and racism in the Long COVID response;
  • Facilitating data harmonization (i.e., combine data from different sources and provide users with a comparable view of data from different studies);
  • Deploying financial resources from the NIH to create a public-private post-viral research infrastructure and translate research results into treatments and cures for millions;
  • Providing expert guidance and resources to media and policymakers;
  • Expanding public-private partnerships;
  • Leveraging existing post-viral disease knowledge and infrastructure;
  • Connecting policymakers with patients and scientists; and
  • Ensuring meaningful patient participation.

“So many patients have bonded together as the healthcare community has not understood why some patients are asymptomatic and others are suffering moderate to debilitating issues a year later,” said Hunter Howard, chairman of the Global Pandemic Coalition, a founder of the Alliance. “As one of the first infected in Texas, and a healthcare executive, I immediately noticed doctor friends did not understand my lingering symptoms or the novel coronavirus.  We started the Global Pandemic Coalition to bring together private companies to support the public sector pandemic initiatives.  If the vaccines continue to drive down mortalities, nothing may be more important now than coming together to drive understanding and fund research for the COVID survivors.”

To accompany the Long COVID Alliance’s launch, the initial partners from 2020 have drafted key recommendations and guidance for the National Institutes of Health (NIH), which can be found by visiting https://longcovidalliance.org/wp-content/uploads/2021/02/NIH-Long-COVID-Alliance-NIH-Recommendations-Letter-Final-with-signers.pdf

Current Long COVID Alliance partners include:

  • Action for M.E.
  • American Medical Women’s Association (AMWA)
  • Bateman Horne Center
  • Body Politic
  • Covid-19 Longhauler Advocacy Project
  • Dysautonomia International
  • ENIGMA COVID-19 Working Group
  • Florida Society of Neurology
  • HADASSAH
  • Health Rising
  • Healthy Women
  • Institute for Neuro-Immune Medicine (INIM)
  • Kantor Neurology, LLC
  • Long COVID Physio
  • Massachusetts ME/CFS & FM
  • #MEACTION
  • ME International
  • Medical Partnership 4 MS+
  • Minnesota ME/CFS Alliance
  • National Association for Nurse Practitioners in Women’s Health
  • National Health Council
  • National Organization for Women (NOW)
  • Nurse Practitioners in Women’s Health (NPWH)
  • Open Medicine Foundation
  • PandoraORG
  • PolyBio Research Foundation
  • Pulmonary Wellness Foundation
  • Sex and Gender Health Collaboration
  • Simmaron Research
  • Solve M.E.
  • The American Dysautonomia Institute (ADI)
  • The Mast Cell Disease Society, Inc.
  • The SHANE Foundation
  • Utah COVID-19 Long Hauler
  • Whittemore Peterson Institute
  • YOU + ME Registry (Solve M.E.)

“Many long haulers are now approaching a full year post-infection. We have lost jobs, lost significant quality of life, and lost pieces of who we once were. It’s been a long road with an uncertain future and we’ve finally found hope,” said Karyn Bishof, Founder of the COVID-19 Longhauler Advocacy Project and of the Long COVID Alliance. “With the help of our partners, we will ensure that Long haulers are not left out in the cold. The Long COVID Alliance will fight with us for awareness, answers, and ensuring that patient voices are included at every step of solving this ‘second wave’ Long COVID health crisis.”

To learn more, join the Long COVID Alliance, or become a signatory to the NIH letter, visit: www.longcovidalliance.org.

About Solve M.E.
The Solve ME/CFS Initiative (Solve M.E.) is the leading, national non-profit organization solely dedicated to solving ME/CFS. We are committed to making ME/CFS understood, diagnosable, and treatable. Solve M.E. is the largest U.S. provider of private competitive research funding exclusively for ME/CFS working to accelerate the discovery of safe and effective treatments; we strive for an aggressive expansion of funding for research that will lead to a cure, and seek to engage the entire ME/CFS community.

Media Inquiries Only 
Contact Emily Taylor
Director of Advocacy and Communications
714-296-1661
ETaylor@solvecfs.org

Managing COVID-19 post viral Fatigue Syndrome

Abstract:

In online surveys, over 50% of persons who contract COVD-19 experience symptoms lasting longer than 90 days [Pelanti S, Grassi E, Markris N, et al. J Psych Res. 2020. doi:10.1016/j.jpsychires.2020.08.008] Despite an estimated 3 million Americans being affected by COVID post-viral fatigue, there has been little discussion about the care of these patients, most of whom report feeling unsupported or dismissed by their providers [Amitay O, Komaroff AL. The Guardian, 20 Aug 2020]. This article points out the similarity between this post-viral fatigue syndrome and Chronic Fatigue Syndrome (ME/CFS) or Systemic Exertion Intolerance Disease (SEID), and offers evidence-based suggestions for management.

Source: Charles W. Lapp & Joseph F. John (2021) Managing COVID-19 post viral Fatigue Syndrome, Fatigue: Biomedicine, Health & Behavior, DOI: 10.1080/21641846.2021.1890347  (Full text) https://www.tandfonline.com/doi/full/10.1080/21641846.2021.1890347

Will COVID-19 Lead to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome?

Introduction:

“Recovering” from COVID-19 does not guarantee a return to a person’s usual state of health. For one thing, some people with multi-system injury—particularly to the brain, heart and kidneys—may develop permanent dysfunction of those organs.

In addition, a more subtle form of chronic illness may develop. For some people with COVID-19, even those who are only mildly affected at first, the ensuing weeks and months of “recovery” bring a surprise and a betrayal: they do not return to full health. Although nucleic acid tests no longer detect the virus, people still suffer from ongoing symptoms. They call themselves “long haulers,” and the condition is being called “long COVID.”

Source: Komaroff AL, Bateman L. Will COVID-19 Lead to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome? Front Med (Lausanne). 2021 Jan 18;7:606824. doi: 10.3389/fmed.2020.606824. PMID: 33537329; PMCID: PMC7848220. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7848220/ (Full text)

Persistent Brainstem Dysfunction in Long-COVID: A Hypothesis

Abstract:

Long-COVID is a postviral illness that can affect survivors of COVID-19, regardless of initial disease severity or age. Symptoms of long-COVID include fatigue, dyspnea, gastrointestinal and cardiac problems, cognitive impairments, myalgia, and others. While the possible causes of long-COVID include long-term tissue damage, viral persistence, and chronic inflammation, the review proposes, perhaps for the first time, that persistent brainstem dysfunction may also be involved.

This hypothesis can be split into two parts. The first is the brainstem tropism and damage in COVID-19. As the brainstem has a relatively high expression of ACE2 receptor compared with other brain regions, SARS-CoV-2 may exhibit tropism therein. Evidence also exists that neuropilin-1, a co-receptor of SARS-CoV-2, may be expressed in the brainstem. Indeed, autopsy studies have found SARS-CoV-2 RNA and proteins in the brainstem. The brainstem is also highly prone to damage from pathological immune or vascular activation, which has also been observed in autopsy of COVID-19 cases.

The second part concerns functions of the brainstem that overlap with symptoms of long-COVID. The brainstem contains numerous distinct nuclei and subparts that regulate the respiratory, cardiovascular, gastrointestinal, and neurological processes, which can be linked to long-COVID. As neurons do not readily regenerate, brainstem dysfunction may be long-lasting and, thus, is long-COVID. Indeed, brainstem dysfunction has been implicated in other similar disorders, such as chronic pain and migraine and myalgic encephalomyelitis or chronic fatigue syndrome.

Source: Yong SJ. Persistent Brainstem Dysfunction in Long-COVID: A Hypothesis. ACS Chem Neurosci. 2021 Feb 4;12(4):573–80. doi: 10.1021/acschemneuro.0c00793. Epub ahead of print. PMID: 33538586; PMCID: PMC7874499. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7874499/ (Full text)

Prevalence and correlates of chronic fatigue syndrome and post-traumatic stress disorder after the outbreak of the COVID-19

Abstract:

As the SARS-COV-2 becomes a global pandemic, many researchers have a concern about the long COVID-19 complications. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a persistent, debilitating, and unexplained fatigue disorder. We investigated psychological morbidities such as CFS and post-traumatic stress disorder (PTSD) among survivors of COVID-19 over 6 months.

All COVID-19 survivors from the university-affiliated hospital of Tehran, Iran, were assessed 6 months after infection onset by a previously validated questionnaire based on the Fukuda guidelines for CFS/EM and DSM-5 Checklist for PTSD (The Post-traumatic Stress Disorder Checklist for DSM-5 or PCL-5) to determine the presence of stress disorder and chronic fatigue problems. A total of 120 patients were enrolled. The prevalence rate of fatigue symptoms was 17.5%. Twelve (10%) screened positive for chronic idiopathic fatigue (CIF), 6 (5%) for CFS-like with insufficient fatigue syndrome (CFSWIFS), and 3 (2.5%) for CFS. The mean total scores in PCL-5 were 9.27 ± 10.76 (range:0-44), and the prevalence rate of PTSD was 5.8%. There was no significant association after adjusting between CFS and PTSD, gender, comorbidities, and chloroquine phosphate administration.

The obtained data revealed the prevalence of CFS among patients with COVID-19, which is almost similar to CFS prevalence in the general population. Moreover, PTSD in patients with COVID-19 is not associated with the increased risk of CFS. Our study suggested that medical institutions should pay attention to the psychological consequences of the COVID-19 outbreak.

Source: Simani L, Ramezani M, Darazam IA, Sagharichi M, Aalipour MA, Ghorbani F, Pakdaman H. Prevalence and correlates of chronic fatigue syndrome and post-traumatic stress disorder after the outbreak of the COVID-19. J Neurovirol. 2021 Feb 2:1–6. doi: 10.1007/s13365-021-00949-1. Epub ahead of print. PMID: 33528827; PMCID: PMC7852482.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7852482/ (Full text)

Chronic COVID-19 Syndrome and Chronic Fatigue Syndrome (ME/CFS) following the first pandemic wave in Germany: a first analysis of a prospective observational study

Abstract:

Objective: Characterization of the clinical features of patients with persistent symptoms after mild to moderate COVID-19 infection and exploration of factors associated with the development of Chronic COVID-19 Syndrome (CCS). Methods: Setting: Charite Fatigue Center with clinical immunologists and rheumatologist, neurologists and cardiologists at Charite University hospital.

Participants: 42 patients who presented with persistent moderate to severe fatigue six months following a mostly mild SARS-CoV-2 infection at the Charite Fatigue Center from July to November 2020.

Main outcome measures: The primary outcomes were clinical and paraclinical data and meeting diagnostic criteria for Chronic Fatigue Syndrome (ME/CFS). Relevant neurological and cardiopulmonary morbidity was excluded.

Results: The median age was 36.5, range 22-62, 29 patients were female and 13 male. At six months post acute COVID-19 all patients had fatigue (Chalder Fatigue Score median 25 of 33, range 14-32), the most frequent other symptoms were post exertional malaise (n=41), cognitive symptoms (n=40), headache (n=38), and muscle pain (n=35). Most patients were moderately to severely impaired in daily live with a median Bell disability score of 50 (range 15-90) of 100 (healthy) and Short Form 36 (SF36) physical function score of 63 (range 15-80) of 100. 19 of 42 patients fulfilled the 2003 Canadian Consensus Criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). These patients reported more fatigue in the Chalder Fatigue Score (p=0.006), more stress intolerance (p=0.042) and more frequent and longer post exertional malaise (PEM) (p= 0.003), and hypersensitivity to noise (p=0.029), light (p=0.0143) and temperature (0.024) compared to patients not meeting ME/CFS criteria. Handgrip force was diminished in most patients compared to healthy control values, and lower in CCS/CFS compared to non-CFS CCS (Fmax1 p=0.085, Fmax2, p=0.050, Fmean1 p=0.043, Fmean2 p=0.034, mean of 10 repeat handgrips, 29 female patients). Mannose-binding lectin (MBL) deficiency was observed frequently (22% of all patients) and elevated IL-8 levels were found in 43% of patients.

Conclusions: Chronic COVID-19 Syndrome at months 6 is a multisymptomatic frequently debilitating disease fulfilling diagnostic criteria of ME/CFS in about half of the patients in our study. Research in mechanisms and clinical trials are urgently needed.

Source: Claudia Kedor, Helma Freitag, Lil-Antonia Meyer-Arndt, Kirsten Wittke, thomas Zoller, Fridolin Steinbeis, Milan Haffke, Rudolf Gordon, Bettina Heidecker, Hans Dieter Volk, Carsten Skurk, Friedemann Paul, Judith Bellmann-Strobl, Carmen Scheibenbogen. Chronic COVID-19 Syndrome and Chronic Fatigue Syndrome (ME/CFS) following the first pandemic wave in Germany: a first analysis of a prospective observational study. medRxiv 2021.02.06.21249256; doi: https://doi.org/10.1101/2021.02.06.21249256 https://www.medrxiv.org/content/10.1101/2021.02.06.21249256v1

Will COVID-19 Lead to ME/CFS?

INTRODUCTION:

“Recovering” from COVID-19 does not guarantee a return to a person’s usual state of health. For one thing, some people with multi-system injury—particularly to the brain, heart and kidneys—may develop permanent dysfunction of those organs.
In addition, a more subtle form of chronic illness may develop. For some people with COVID-19, even those who are mildly affected at first, the ensuing weeks and months of “recovery” bring a surprise and a betrayal: they do not return to full health. Although nucleic acid tests no longer detect the virus, people still suffer from ongoing symptoms. They call themselves “long haulers”, and the condition is being called “long COVID”.

Source: Anthony L. Komaroff and Lucinda Bateman. Will COVID-19 Lead to ME/CFS? Front. Med. | doi: 10.3389/fmed.2020.606824 https://www.frontiersin.org/articles/10.3389/fmed.2020.606824/full (Full text)

COVID-19 and chronic fatigue syndrome: Is the worst yet to come?

Abstract:

There has been concern about possible long-term sequelae resembling myalgic encephalomyelitis/chronic fatigue syndrome in COVID-19 patients. Clarifying the mechanisms underlying such a “post-COVID-19 fatigue syndrome” is essential for the development of preventive and early treatment methods for this syndrome.

In the present paper, by integrating insights pertaining to the glymphatic system and the nasal cerebrospinal fluid outflow pathway with findings in patients with chronic fatigue syndrome, idiopathic intracranial hypertension, and COVID-19, I provide a coherent conceptual framework for understanding the pathophysiology of post-COVID-19 fatigue syndrome. According to this hypothesis, this syndrome may result from damage to olfactory sensory neurons, causing reduced outflow of cerebrospinal fluid through the cribriform plate, and further leading to congestion of the glymphatic system with subsequent toxic build-up within the central nervous system. I further postulate that patients with post-COVID-19 fatigue syndrome may benefit from cerebrospinal fluid drainage by restoring glymphatic transport and waste removal from the brain.

Obviously, further research is required to provide further evidence for the presence of this post-viral syndrome, and to provide additional insight regarding the relative contribution of the glymphatic-lymphatic system to it. Other mechanisms may also be involved. If confirmed, the glymphatic-lymphatic system could represent a target in combating post-COVID-19 fatigue syndrome. Moreover, further research in this area could also provide new insights into the understanding of chronic fatigue syndrome.

Source: Wostyn P. COVID-19 and chronic fatigue syndrome: Is the worst yet to come? Med Hypotheses. 2021 Jan 2;146:110469. doi: 10.1016/j.mehy.2020.110469. Epub ahead of print. PMID: 33401106. https://pubmed.ncbi.nlm.nih.gov/33401106/

Could Cognitive Behavioural Therapy Be an Effective Treatment for Long COVID and Post COVID-19 Fatigue Syndrome? Lessons from the Qure Study for Q-Fever Fatigue Syndrome

Abstract:

An increasing number of young and previously fit and healthy people who did not require hospitalisation continue to have symptoms months after mild cases of COVID-19. Rehabilitation clinics are already offering cognitive behavioural therapy (CBT) as an effective treatment for long COVID and post-COVID-19 fatigue syndrome based on the claims that it is effective for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-the most common post-infectious syndrome-as no study into the efficacy of CBT for post-COVID-19 fatigue syndrome has been published. Re-analyses of these studies, however, showed that CBT did not lead to objective improvements in heterogeneous groups of ME/CFS patients, nor did it restore the ability to work.

The group of patients with long COVID and post-COVID-19 fatigue syndrome, on the other hand, is homogeneous. We therefore analysed the Dutch Qure study, as it studied the efficacy of CBT in a homogeneous group of patients who developed Q-fever fatigue syndrome-which affects up to 30% of patients-after the largest reported outbreak of Q-fever, to see if CBT might potentially be an effective treatment for long-haulers after COVID-19 infection.

Our reanalysis found that the Qure study suffered from many serious methodological problems, which included relying on one subjective primary outcome in a study without a control group for the non-blinded CBT treatment group, using a post hoc definition of improvement, waiting 2 years before publishing their objective actometer results and ignoring the null effect of said results. Moreover, only 10% of participants achieved a clinically meaningful subjective improvement in fatigue as a result of CBT according to the study’s own figures.

Consequently, CBT has no subjective clinically meaningful effect in nine out of every ten patients that are treated with it. Additionally, the subjective improvement in fatigue was not matched by an improvement in disability, even though the disability was fatigue related according to the researchers. On top of this, CBT did not lead to an objective improvement in physical performance. Therefore, it cannot be said that CBT is an effective treatment for Q-fever fatigue syndrome either. It seems therefore unlikely that CBT will reduce disability or lead to objective improvement in long COVID or in post-COVID-19 fatigue syndrome.

Source: Vink M, Vink-Niese A. Could Cognitive Behavioural Therapy Be an Effective Treatment for Long COVID and Post COVID-19 Fatigue Syndrome? Lessons from the Qure Study for Q-Fever Fatigue Syndrome. Healthcare (Basel). 2020 Dec 11;8(4):E552. doi: 10.3390/healthcare8040552. PMID: 33322316. https://www.mdpi.com/2227-9032/8/4/552 (Full text)