1 in 8 Covid-19 patients develop long Covid, finds research

The most reliable estimates to date suggest one in eight (12.7%) Covid-19 patients develop long Covid symptoms.

A large Dutch study provides one of the first comparisons of long-term symptoms after SARS-CoV-2 infection in an uninfected population, as well as measuring symptoms in individuals both pre- and post-Covid-19 infection.

The inclusion of uninfected populations enables a more accurate prediction of long-term Covid-19 symptom prevalence as well as improved identification of the core symptoms of long Covid.

‘There is urgent need for data informing the scale and scope of the long-term symptoms experienced by some patients after COVID-19 illness,’ said Prof Judith Rosmalen from the University of Groningen, lead author of the study. ‘However, most previous research into long COVID has not looked at the frequency of these symptoms in people who haven’t been diagnosed with COVID-19 or looked at individual patients’ symptoms before the diagnosis of COVID-19.’

Prof Rosmalen continued: ‘Our study approach looks at the symptoms most often associated with long COVID, including breathing problems, fatigue and loss of taste and/or smell, both before a COVID-19 diagnosis and in people who have not been diagnosed with COVID-19.

‘This method allows us to take pre-existing symptoms and symptoms in non-infected people into account to offer an improved working definition for long COVID and provide a reliable estimate at how likely long COVID-19 is to occur in the general population.’

person in blue jacket holding white textile

In this new study conducted in the Netherlands, researchers collected data by asking participants of the population-based Lifelines COVID-19 Cohort to regularly fill out digital questionnaires on 23 symptoms commonly associated with long COVID.

The questionnaire was sent out 24 times to the same individuals between March 2020 and August 2021 meaning participants who had COVID-19 during this time were infected with the SARS-CoV-2 alpha-variant or earlier variants. Most of the data was collected before the COVID-19 vaccine rollout in The Netherlands so the number of vaccinated participants was too small to analyse in this study.

Participants were recorded as COVID-19 positive if they had either a positive test or a doctor’s diagnosis of COVID-19. Of 76,422 participants, 4,231 (5.5%) participants who had COVID-19 were matched to 8,462 controls taking account of sex, age and time of completing questionnaires that indicated a COVID-19 diagnosis.

The researchers found that several symptoms were new or more severe three to five months after having COVID-19, compared to symptoms before a COVID-19 diagnosis and to the control group, suggesting these symptoms can be viewed as the core symptoms of long COVID.

The core symptoms recorded were chest pain, difficulties breathing, pain when breathing, painful muscles, loss of tase and/or smell, tingling hands/feet, a lump in throat, alternately feeling hot and cold, heavy arms and/or legs and general tiredness. The severity of these symptoms plateaued at three months after infection with no further decline.

Other symptoms that did not significantly increase three to five months after a COVID-19 diagnosis included headache, itchy eyes, dizziness, back pain and nausea.

Photo by Mufid Majnun


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