More than 500 million people worldwide have been infected with the coronavirus and it was already clear that some of them suffer from health problems. The size of this group has remained uncertain until now, while governments desperately need this information as a basis for policy and research.
There are already dozens of attempts has been done to capture the so-called post-covid syndrome in numbers, but many studies have quite a few shortcomings as a result of which unrealistic calculations have been published. Numerous patients report medical complaints after a corona infection, but how many of them already had these complaints before? And how certain is it that their problems were caused by the coronavirus itself and not by, for example, the stress that the pandemic brought with it?
Ongoing health research
Dutch scientists managed to circumvent these shortcomings by linking up with an existing health survey (Lifelines) in which 167 thousand people from the North of the Netherlands have been followed for years. Quite soon after the outbreak of the virus, part of that group also started filling in questionnaires about corona on a regular basis. More than 4,200 participants contracted a corona infection and they kept the researchers from the Groningen UMCG and Radboud UMC in Nijmegen informed about their health situation for months.
Because it was also known how they were before the infection, a good comparison could be made. In addition, the researchers were able to compare complaints from the group of corona patients with those of a comparable group of participants who had not been infected, in order to correct the data for a possible pandemic stress effect. In this way they managed to paint a much more accurate picture of the number of patients than has been done until now.
More than 21 percent of the corona patients in the study had at least one new health complaint or an ailment that had worsened three to five months after the infection. In the uninfected group this was just under 9 percent. Conclusion: in more than 12 percent of patients, the complaints are the result of the corona infection.
Ten symptoms
Ten symptoms were so obvious or exacerbated that the researchers consider them to be the basic hallmarks of post-covid syndrome. These include chest pain, aching muscles, heaviness in arms and legs, loss of smell and taste and general fatigue. The patients were not asked about mental complaints, such as the so-called brain fog (difficulty with concentration and memory); that a corona infection can also cause those symptoms was only known months after the start of the study.
The results mainly apply to patients with relatively mild infections, who have been sick at home. Only a few percent of the participants had been hospitalized. It is known that 50 to 70 percent of patients admitted to hospital with covid do not recover well.
British professor of pulmonary medicine Christopher Brightling and his colleague pulmonologist Rachael Evans praise the Dutch research in an accompanying commentary. The number of patients whose complaints ultimately lead to serious health damage or disability is therefore a small minority, they note.
The Dutch scientists collected by far the most data during the first corona year. Whether vaccination is effective against the development of long-term complaints and whether the recent variants of the virus (delta and omikron) patients hit like that is therefore unknown.