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"Characterising Long Covid in an International Cohort" - new Long Covid research



@wearebodypolicitc have just released their research as a preprint. A preprint is a full draft research paper that is shared publicly before it has been peer reviewed ( ie by the scientific/medical community). I have put the link to the article in my bio. It is also here for those of you who have subscribed to my blog - https://www.medrxiv.org/content/10.1101/2020.12.24.20248802v2.


Many of us who caught Covid-19 in the first wave who went onto Long Covid, and did every survey known to man to try to advance knowledge of LC, probably would have taken part. It is called

Characterizing Long COVID in an International Cohort: 7 Months of Symptoms and Their Impact by Davis et al.

I have included below the abstract that has been published and will then go onto discuss some of the results.

Aim To characterize the symptom profile and time course in patients with Long COVID, along with the impact on daily life, work, and return to baseline health.

Design International web-based survey of suspected and confirmed COVID-19 cases with illness lasting over 28 days and onset prior to June 2020.

Setting Survey distribution via online COVID-19 support groups and social media

Participants 3,762 respondents from 56 countries completed the survey. 1166 (33.7%) were 40-49 years old, 937 (27.1%) were 50-59 years old, and 905 (26.1%) were 30-39 years old. 2961 (78.9%) were women, 718 (19.1%) were men, and 63 (1.7%) were nonbinary. 8.4% reported being hospitalized. 27% reported receiving a laboratory-confirmed diagnosis of COVID-19. 96% reported symptoms beyond 90 days.

Results Prevalence of 205 symptoms in 10 organ systems was estimated in this cohort, with 66 symptoms traced over seven months. Respondents experienced symptoms in an average of 9.08 (95% confidence interval 9.04 to 9.13) organ systems. The most frequent symptoms reported after month 6 were: fatigue (77.7%, 74.9% to 80.3%), post-exertional malaise (72.2%, 69.3% to 75.0%), and cognitive dysfunction (55.4%, 52.4% to 58.8%). These three symptoms were also the three most commonly reported overall. In those who recovered in less than 90 days, the average number of symptoms peaked at week 2 (11.4, 9.4 to 13.6), and in those who did not recover in 90 days, the average number of symptoms peaked at month 2 (17.2, 16.5 to 17.8). Respondents with symptoms over 6 months experienced an average of 13.8 (12.7 to 14.9) symptoms in month 7. 85.9% (84.8% to 87.0%) experienced relapses, with exercise, physical or mental activity, and stress as the main triggers. 86.7% (85.6% to 92.5%) of unrecovered respondents were experiencing fatigue at the time of survey, compared to 44.7% (38.5% to 50.5%) of recovered respondents. 45.2% (42.9% to 47.2%) reported requiring a reduced work schedule compared to pre-illness and 22.3% (20.5% to 24.3%) were not working at the time of survey due to their health conditions.

Conclusions Patients with Long COVID report prolonged multisystem involvement and significant disability. Most had not returned to previous levels of work by 6 months. Many patients are not recovered by 7 months, and continue to experience significant symptom burden.


My discussion

This is a very important study as it is the first to characterise LC. It has a relatively large sample size (3762 respondents) so is likely to be significant. 79% were women, but as we know women are more likely to engage in patient support groups, 34 % were those between 40-49 years of age.


It follows the lived experience of those suffering with LC for over 7 months since they contracted the acute infection. They demonstrate a large range of multi-systemic symptoms. The most likely early symptoms were fatigue, dry cough, shortness of breath, headaches, muscle aches, chest tightness, and sore throat. They found that presence of fever, which has widely been used for screening purposes was found only 30% of participants.

The figure below nicely shows the initial peaks of these symptoms:



It is important to note that their analysis confirmed that, with the exception of change to smell and taste, symptoms are not significantly different between those who test positive for SARS-CoV-2 and those who test negative but felt they had had Covid-19. (Compare orange to blue line above.

85% had cognitive symptoms ( memory, thinking and problem solving/ brain fog) and this was present in all age groups. 86% of respondents had gastro-intestinal symptoms - diarrhoea being the most common.


The most likely symptoms to persist after month 6 were

  • fatigue

  • post-exertional malaise

  • cognitive dysfunction (“brain fog”)

  • neurologic sensations (neuralgias, weakness, coldness, electric shock sensations, facial paralysis/pressure/numbness)

  • headaches

  • insomnia

  • muscle aches

  • palpitations

  • shortness of breath

  • dizziness/balance issues

  • speech and language issues.


Of those that had not recovered by 90 days peak incidence of symptoms was 2 months ( see figure below)



Post-exertional malaise (PEM) was found to be highly represented in this study (89.1% at any time during the course of illness, 72.2% at month 7). Many may meet the diagnostic criterai for ME/CFS>

34 % had the diagnostic criteria for Positional Orthostatic Tachycardia Syndrome.

The most debilitating symptoms were:

  • Fatigue

  • Breathing issues

  • Cognitive function.


There was reduced work capacity because of cognitive dysfunction, in addition to other debilitating symptoms, translated into the loss of hours, jobs, and ability to work relative to pre-illness levels. 68.9% of unrecovered respondents reported reduced work hours or not working at all as a direct result of their COVID-19 illness, and on average the unrecovered group felt they were less than 60% returned to their pre-illness baseline.

Pacing was the most highly rated management approach which was significantly helpful to 25% and 18% found it slightly helpful.

There is so much useful information in this paper that I would run the risk of just rewriting it! For anyone suffering from LC it is a very validating research. Hopefully it will open researchers eyes to the key issues of LC and direct research funds accordingly.


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