Largest ever mapping of long-term symptoms of COVID-19

​Patients most severely affected by COVID-19 who had to spend many days bedridden have the most severe long-term post-infection problems. This is documented in a new study, in which researchers have monitored people for more than two years after they were infected with COVID-19.

If you were bedridden for many days when the COVID-19 pandemic struck, you have probably also experienced a number of symptoms for a long period afterwards. Researchers have found a direct link between the severity of COVID-19 infection and long-term physical symptoms. This is confirmed in the hitherto largest study of its kind. A group of Danish and foreign researchers are behind the study, and the results have been published in The Lancet Regional Health - Europe

In October 2023, the World Health Organisation (WHO) received reports of more than 771 million incidents of COVID-19. It transpired that between 10% and 20% of these people are still experiencing long-term symptoms.

The new study is the first in which researchers have investigated long-term consequences for up to two years after COVID-19 infection among people who have not been in contact with a hospital in connection with the infection. This is according to Associate Professor Ole B. Pedersen, consultant at the Department of Clinical Immunology, Zealand University Hospital, and one of the authors of the study.

- People who were hardest hit by COVID-19, and were confined to bed for at least seven days, turned out to have the most physical symptoms which continued for up to two years after diagnosis. This underlines the importance of monitoring physical symptoms for a longer period after diagnosis, particularly for people who have been seriously ill with COVID-19, says Ole B. Pedersen.

More than one in four bedridden

The results show that 28% of all those struck by COVID-19 were bedridden, and just under 10% had to lie in bed for more than a week. The longer they were bedridden, the greater the risk they would suffer from long-term symptoms, especially respiratory problems, dizziness, rapid heartbeat and headache. The prevalence of symptoms was generally 37% higher in the group of people who had had COVID-19 than for people who had not been infected. This is according to Maria Didriksen, a researcher at the Department of Clinical Immunology at Copenhagen University Hospital - Rigshospitalet and the main author of the study.

- Only around one percent of all patients were so severely affected that they had to be admitted to hospital. Our research draws a picture of how things went for the millions of people infected who laid sick at home. We can see that many have had to struggle with symptoms for a long time after, but nevertheless it's comforting new knowledge that the risk of experiencing longer-term symptoms is no higher than for others if you were not confined to bed for more than a week with the disease, says Maria Didriksen.

The study is based on a questionnaire survey of 64,880 adults with longer-term corona symptoms from Denmark, Sweden, Norway and Iceland. The participants reported on their experience of a number of negative physical symptoms in the period April 2020 to August 2022. More than 22,000 of the participants had tested positive for COVID-19 in the period, and almost 10% of the group were confined to bed for at least seven days. Those with a COVID-19 diagnosis experienced more severe physical symptoms compared with those who had not been diagnosed. Patients who had been bedridden with COVID-19 for at least seven days had the highest prevalence of severe physical symptoms which continued for up to two years after diagnosis.

Long-term health effects are still being investigated

The study is part of the international collaboration project COVIDMENT, headed by Professor Thomas Werge from the Institute of Biological Psychiatry at Sct. Hans Psychiatric Hospital in Roskilde, Denmark. The project includes studies to assess the long-term health effects of the COVID-19 pandemic, including the impact of the disease on cognitive function, mental health and social isolation.

The research team notes that long-term COVID-19 symptoms are still subject to research, and the causes and prevalence of the disease are still being investigated.

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