Long COVID: studies reporting on long-term follow up on COVID-19
Simon Collins, HIV i-Base
The following recent papers add to the growing complexity of defining and managing long term complications of COVID-19.
This includes accurately attributing a broad range of symptoms to COVID-19 and understanding when this might be an outcome from time in intensive care units, especially if intubated.
Previous reports in HTB have previously included studies where severity and duration of initial COVID-19 is not directly linked to risk of developing long COVID.
UK study reports 71% of people still have symptoms after five months
A multi centre observational study from the UK reports on longer term follow-up in 1077 participants hospitalised with COVID-19 in 2000. 
Characteristics of the group included 36% women, mean age 58 years (+/– SD 13), 69% white ethnicity, 27% mechanical ventilation, and 50% had at least two co-morbidities. Participants were assessed after a median of 5 (IQR: 4 to 6).
Overall, 71% still reported symptoms and 29% felt fully recovered. Other results included 20% reporting a new disability, and 19% having health-related change in their job.
In multivariate analysis, the following factors were associated with failure to recover: being female, middle-age, white ethnicity, two or more co-morbidities, and more severe acute illness.
French study reports symptoms are still commonly reported after four months
This prospective study of 478 participants who were hospitalised with COVID-19 from March to May 2020 at a single hospital in France were contacted by phone four months after discharge. 
At least one new onset symptom was commonly reported (51%). These included fatigue in 134/431 (31%), cognitive symptoms in 86/416 (21%), and dyspnea in 78/478 (16%).
CT lung abnormalities were reported in 63% of 171 participants who visited the clinic (mainly subtle ground-glass opacities). Fibrotic lesions were observed in 19% of these 171 patients.
A related editorial in JAMA comments thatstudy is one of the first studies to systematically and comprehensively report the medical outcomes of COVID-19 survivors. 
The editorial comments that in addition to needing more studies looking at longer-term outcomes, recovery clinics also need to be expanded to provide support for this population.
US matched case-control study reports new symptoms 1-4 months after hospitalisation
A matched case-control study from the US also reported that 7% of people hospitalised with COVID-19 reported new symptoms within 1 to 4 months. 
Adults with COVID-19 were 2.8 times more likely to experience acute pulmonary embolism as compared to controls. They were also more likely to report a range of other conditions including nonspecific chest pain, fatigue, headache, and respiratory, nervous, circulatory and GI system symptoms).
These differences were not reported for children.
Pre-review community study on long COVID
A paper published in pre-review format includes 7-month follow-up of symptoms from a large international community survey. 
The group analysed responses from 3,762 participants. Of these 1,020 were laboratory confirmed and 2742 were suspected or untested. Participants reported from 56 countries, with illness duration of at least 28 days. Nearly all (96%) reported symptoms that continued for more than three months.
Although the paper includes analyses of patterns of symptoms, the self-selection to participate and high proportion of people with unconfirmed COVID-19 might explain why this paper has been on the pre-review website four months after it was first posted.
- Evans RA et al. Physical, cognitive and mental health impacts of COVID-19 following hospitalisation: a multi-centre prospective cohort study. Pre-review paper. doi.org/10.1101/2021.03.22.21254057. (25 March 2021).
- COMEBAC Study Group. Four-month clinical status of a cohort of patients after hospitalization for COVID-19. JAMA. doi:10.1001/jama.2021.3331. (17 March 2021).
- Prescott HC et al. Outcomes for patients following hospitalization for COVID-19. JAMA editorial. 325(15):1511-1512. doi:10.1001/jama.2021.3430.
- Chevinsky JR et al. Late conditions diagnosed 1–4 months following an initial COVID-19 encounter: a matched cohort study using inpatient and outpatient administrative data — United States, March 1–June 30, 2020. Clinical Infectious Diseases, ciab338, doi: 10.1093/cid/ciab338. (28 April 2021).
- Davis HE et al. Characterizing long COVID in an international cohort: 7 months of symptoms and their impact. Pre-review draft. MedRxiv. DOI: 10.1101/2020.12.24.20248802. (5 April 201).