Understanding Long COVID-19

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Last Updated: May 7, 2021

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This Briefing Note was completed by the Evidence Synthesis Unit (Research, Analysis and Evaluation Branch, Ministry of Health) in collaboration with a member of the COVID-19 Evidence Synthesis Network. Please refer to the Methods section for further information.

Purpose

This note summarizes the research evidence associated with “long COVID”, including definitions, risk factors (i.e., sex/gender, age), symptomatology, prognosis, therapeutics, and other emerging research findings.

*The full version of the Briefing Note including the Appendix can be accessed in the PDF file at the top of the page*

Key Findings

Commonly, long COVID is characterized as the persistence of any COVID signs and symptoms that continue or develop between four to 12 weeks after acute COVID-19, including both ongoing symptomatic COVID‑19 and post‑COVID‑19 syndrome.

Limitations

The limited evidence base currently precludes a precise definition of long COVID-19 symptoms and prevalence. In addition, no identified studies provided evidence regarding prognosis for individuals with long COVID. There is a clear need for robust, controlled, prospective cohort studies, including different at-risk populations and settings, incorporating appropriate investigations, collected and recorded in a standardised way.

Analysis for Ontario

Since the time frame for assessing the risk factors and symptoms associated with long COVID has just been seven months, there has been scant time to understand the longer-term implications of COVID-19 infection. The knowledge regarding long term effects and treatment options is still evolving.

Supporting Evidence

This section below summarizes the emerging research evidence associated with ‘long COVID’, including definitions, risk factors, symptomatology, prognosis, and emerging trends or findings.

Scientific Evidence

  • ‘Long COVID’ Defined: The hashtag ‘#Long COVID’ has been frequently used in social media; however, according to the identified literature, long COVID lacks a commonly accepted case definition. Commonly, long COVID is characterized as the persistence of any COVID signs and symptoms that continue or develop between four to 12 weeks after acute COVID-19, including both ongoing symptomatic COVID‑19 and post‑COVID‑19 syndrome. More formal definitions have also been proposed.
  • Emerging Research Findings: Sixteen systematic, narrative, and living reviews and four studies yielded the following details:
    • Risk factors: The following factors may increase the risk for long COVID: a higher acuity of COVID-19 infection or presence of many acute COVID-19 symptoms, having a higher body mass index (e.g., obesity), pre-existing comorbidities, psychiatric disorders, and being a health care worker. In addition:
      • Gender: Research suggests women are more likely to develop long COVID than men. One review (2021) suggests women are twice as likely to develop symptoms of long COVID.
      • Older Age: Research suggests people of older age are more likely to develop long COVID. One review (2021) suggests that patients with long COVID are around four years older than those without.
    • Symptomatology: The most common symptoms reported were: fatigue, dyspnea (e.g., shortness of breath), headache, and pain (e.g., chest, joint, muscle); however, persistent symptoms have also been described for the cognitive, musculoskeletal, respiratory, gastrointestinal, cardiac, and psychological systems.
  • Management of Long COVID Patients: Research suggests that treating people with long COVID requires a multidisciplinary approach including evaluation, symptomatic treatment, treatment of underlying problems, physiotherapy, occupational therapy and psychological support.
    • Treatment of Minor Symptoms: Cough, pain, myalgia can be treated symptomatically with paracetamol (i.e., acetaminophen), cough suppressants, and oral antibiotics (if secondary bacterial infection is suspected).
    • Etiology: Etiology behind the symptoms, if any, like pulmonary embolism, cerebrovascular accident, coronary artery disease, has to be treated as per the standard protocol; chest physiotherapy and neuro rehabilitation is important in patients with pulmonary and neuromuscular sequelae.
    • Follow-up: The ideal frequency and duration of follow up is not clearly defined. In people with COVID-19 interstitial pneumonia, in the first 12 months, seven interactions with health care professionals (four face-to-face) are recommended, alongside four high-resolution CT scans, four six-minute walk tests (6MWT); four blood tests (including blood count and metabolic panel); and two SARS-CoV-2-IgG tests (i.e., antibody tests).
    • Social and Economic Impact: As the disease continues to spread, more people may need health care support in the future, which could put more demand on the health care system. Clear guidelines regarding management of long COVID may help clear confusion among health care providers.
  • Limitations: The limited evidence base currently precludes a precise definition of COVID-19 symptoms and prevalence. In addition, no identified studies provided evidence regarding prognosis for individuals with long COVID. There is a clear need for robust, controlled, prospective cohort studies, including different at-risk populations and settings, incorporating appropriate investigations, collected and recorded in a standardized way.

Methods

Individual peer-reviewed articles and review articles were identified through PubMed, and Google Scholar. The search was limited to English sources and therefore may not capture the full extent of initiatives in non-English speaking countries. Full-text results extracted were limited to those available through Open Access or studies made available to the Ministry by our partners.

The COVID-19 Evidence Synthesis Network is comprised of groups specializing in evidence synthesis and knowledge translation. The group has committed to provide their expertise to provide high-quality, relevant, and timely synthesized research evidence about COVID-19 to inform decision makers as the pandemic continues. The following members of the Network provided evidence synthesis products that were used to develop this Evidence Synthesis Briefing Note:

  • Evidence Synthesis Unit, Research Analysis and Evaluation Branch, Ontario Ministry of Health; and
  • COVID-19 Evidence Network to support Decision-making (COVID-END).