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How long is Long-COVID? Symptomatic improvement between 12 and 18 months in a prospective cohort study
  1. Robert M Barker-Davies1,2,
  2. O O’Sullivan1,3,
  3. D A Holdsworth4,5,
  4. P Ladlow1,6,
  5. A Houston1,
  6. R Chamley4,5,
  7. A Greenhalgh1,
  8. E D Nicol7,8 and
  9. A N Bennett1,9
  1. 1Academic Department of Military Rehabilitation, Defence Medical Rehabilitation Centre, Loughborough, UK
  2. 2School of Sport Exercise and Health Sciences, Loughborough University, Loughborough, UK
  3. 3Academic Unit of Injury, Recovery and Inflammation Sciences, University of Nottingham, Nottingham, UK
  4. 4Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK
  5. 5Oxford Heart Centre, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
  6. 6Department for Health, University of Bath, Bath, UK
  7. 7Department of Cardiology, Royal Brompton Hospital, Birmingham, UK
  8. 8School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
  9. 9National Heart and Lung Institute, Imperial College London, London, UK
  1. Correspondence to Group Captain A N Bennett, Academic Department of Military Rehabilitation (ADMR), Defence Medical Rehabilitation Centre, Loughborough, LE12 5BR, UK; alexander.n.bennett{at}


Introduction COVID-19 infection can precede, in a proportion of patients, a prolonged syndrome including fatigue, exercise intolerance, mood and cognitive problems. This study aimed to describe the profile of fatigue-related, exercise-related, mood-related and cognitive-related outcomes in a COVID-19-exposed group compared with controls.

Methods 113 serving UK Armed Forces participants were followed up at 5, 12 (n=88) and 18 months (n=70) following COVID-19. At 18 months, 56 were in the COVID-19-exposed group with 14 matched controls. Exposed participants included hospitalised (n=25) and community (n=31) managed participants. 43 described at least one of the six most frequent symptoms at 5 months: fatigue, shortness of breath, chest pain, joint pain, exercise intolerance and anosmia. Participants completed a symptom checklist, patient-reported outcome measures (PROMs), the National Institute for Health cognitive battery and a 6-minute walk test (6MWT). PROMs included the Fatigue Assessment Scale (FAS), Generalised Anxiety Disorder-7 (GAD-7), Patient Health Questionnaire-9 (PHQ-9) and Patient Checklist-5 (PCL-5) for post-traumatic stress.

Results At 5 and 12 months, exposed participants presented with higher PHQ-9, PCL-5 and FAS scores than controls (ES (effect size) ≥0.25, p≤0.04). By 12 months, GAD-7 was not significantly different to controls (ES <0.13, p=0.292). Remaining PROMs lost significant difference by 18 months (ES ≤0.11, p≥0.28). No significant differences in the cognitive scales were observed at any time point (F=1.96, p=0.167). At 5 and 12 months, exposed participants recorded significantly lower distances on the 6MWT (ηp2≥0.126, p<0.01). 6MWT distance lost significant difference by 18 months (ηp2<0.039, p>0.15).

Conclusions This prospective cohort-controlled study observed adverse outcomes in depression, post-traumatic stress, fatigue and submaximal exercise performance up to 12 months but improved by 18-month follow-up, in participants exposed to COVID-19 compared with a matched control group.

  • COVID-19

Data availability statement

Data are available upon reasonable request.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

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Data availability statement

Data are available upon reasonable request.

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  • Contributors DAH, ANB, EN, PL, OO'S and RB-D conceived the study. DAH, EN and ANB secured funding to deliver the research. RB-D, OO'S, AG, PL and RC acquired data at DMRC. AH and RB-D provided statistical analysis and produced graphs. RB-D, with support from PL, OO'S, AH and ANB, drafted the manuscript. All authors reviewed the manuscript. ANB acted as chief investigator and guarantor for the study.

  • Funding A grant was received from the Defence Medical Services Research Steering Group. No specific funding number was assigned.

  • Disclaimer The Defence Medical Services Research Steering Group had no role in the preparation of this manuscript.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.