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Almost half of all people in hospital because of COVID-19 develop complications, a new study showed. This includes people who are young and previously healthy. The complications developed during the hospital stay and sometimes meant that people needed more support to look after themselves than before their admission.

Complications from COVID-19 include heart disease and stroke, and can affect any part of the body. In this study, researchers detailed complications of COVID-19 which developed during the hospital stay, and the groups of people most likely to be affected. The research should improve understanding of the problems these people might face on leaving hospital. This will help healthcare services prepare to provide appropriate support.

The most common complications related to kidneys (renal), lungs (respiratory) or affected the whole body (systemic) via the bloodstream for example and included blood clotting problems and anaemia. These complications are associated with long-term ill-health and an increased chance of dying.

Even young, previously healthy individuals were at risk of complications which could have a long-term impact on their health. Men were at more risk than women, older people at more risk than younger people. The highest risk was seen in the over 50s who had been admitted to critical care. However, younger people who developed complications tended to need more support to care for themselves once they were home.

What’s the issue?

As of February 2022, more than 18 million people in the UK have been infected with COVID-19. More than 717,000 people have been admitted to hospital as a result.

COVID-19 can affect any part of the body, for instance the heart or kidneys. People who have complications tend to need more help to look after themselves once they have left hospital. Research into the longer-term health issues associated with COVID-19 will inform policymakers about extra health resources that might be needed.

Understanding someone’s chances of developing a complication will inform treatment decisions and long-term planning. It will help people manage their expectations about recovery.

This study describes the complications in people hospitalised with COVID-19. It looks at factors that might increase the risk, such as age, sex, ethnicity, and pre-existing illness.

What’s new?

In early 2020, the researchers looked at data from 73,197 adults with confirmed or strongly suspected COVID-19. The study covered 302 hospitals in the UK. Just over half (56%) of the participants were men; most (81%) had at least one other illness.

The researchers followed people until discharge from hospital or for 28 days if they were not discharged. They found that half (50%) of all patients admitted to hospital with COVID-19 developed complications.

Overall, the most common complications were:

  • renal – in 1 in 4 people (24%)
  • respiratory (related to lungs but not typical of COVID-19) – in almost 1 in 5 (18%)
  • systemic – in 1 in 6 (16.3%).

Other complications were slightly less common. Cardiovascular (heart and blood vessels) complications affected 12% people; gastrointestinal (digestive system) complications affected 11%; and neurological (nervous system) complications affected 4% people.

Different groups of people had different rates. Complications were seen in:

  • 58% Black people versus 49% White people
  • 55% men over 60 versus 48% women over 60
  • 49% men under 60 versus 37% women under 60.

Pre-existing conditions added to the risk. Complication rates were increased among:

  • people with obesity
  • people with pre-existing conditions, which could be made much worse with COVID-19 (those with heart disease, for example, were more likely than other to develop a heart complication)
  • people with more than one pre-existing condition.

People who received respiratory or critical care support while in hospital were also at increased risk. Overall, people in their 60s who had two or more other conditions were some of the most likely to develop complications (58%). Those aged 19-29 years with no other illness had the lowest rate and only one in 5 (21%) developed complications.

Of those with a complication, 1 in 4 needed extra support to care for themselves when they returned home than before their hospital stay. This was particularly so for:

  • under 50s
  • men
  • people who received critical care support while in hospital
  • people who developed neurological complications (such as seizures or strokes).

Almost one in 3 people in this study died (32%). Complications were more common in those who died, especially among younger people. Cardiovascular and respiratory complications were associated with the largest increases in death across all age groups.

Why is this important?

Complications were common in all age groups. COVID-19 and its complications place a burden both on patients and on the healthcare system. This study will help healthcare services plan to provide resources for hospitals, plus the extra support that many people needed after they were discharged.

The researchers found that commonly used hospital scores (such as NEWS2, qSOFA, and the 4C Mortality Score) correlated with complications. These scores might therefore help clinicians to predict the groups of people most at risk of developing long-term complications. The next step is to design interventions to prevent complications.

The research suggests that earlier treatments and improved monitoring would be useful. People with pre-existing conditions would benefit especially.

What’s next?

This study was carried out when COVID-19 first hit the UK, before testing was commonplace and vaccinations had been rolled out.

The researchers would like to explore the complications in more detail to find ways of preventing or treating them. They would like to explore the longer-term outcomes for these patients to see whether they eventually return to health. This would help people to manage their expectations around their own recovery. It would also inform the allocation of healthcare resources.

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This Alert is based on: Drake TM, Riad AM, and others. Characterisation of in-hospital complications associated with COVID-19 using the ISARIC WHO Clinical Characterisation Protocol UK: a prospective, multicentre cohort study. Lancet 2021;398:10296

Work from the same team looking at the clinical features of COVID-19 in hospitalised patients: Docherty AB, Harrison EM, Green CA, and others. Features of 20 133 UK patients in hospital with COVID-19 using the ISARIC WHO Clinical Characterisation Protocol: prospective observational cohort study. BMJ 2020;369:m1985

Funding: This work is supported by grants from the NIHR, the NIHR Imperial Biomedical Research Centre, the NIHR Health Protection Research Unit (HPRU) in Respiratory Infections at Imperial College London, the NIHR HPRU in Emerging and Zoonotic Infections at the University of Liverpool and the NIHR Biomedical Research Centre at Imperial College London.

Conflicts of Interest: The study authors declare a number of potential conflicts.

Disclaimer: NIHR Alerts are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that views expressed in NIHR Alerts are those of the author(s) and reviewer(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.

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