We try to answer the most pressing questions about Long COVID

All of the involved researchers studied a different group of patients, such as patients who, due to a COVID-19 infection, were admitted to the hospital or IC ward or patients who had undergone rehabilitation. We collected the research data from seven such studies. These form the basis for our study into Long COVID: The CORona Follow Up (CORFU) study.

Chahinda: ‘For the CORFU study, we sent out new questionnaires to all participants of the seven previous studies. Our questions concerned the symptoms after their COVID-19 infection. How do the patients from then feel now? Did they develop lingering symptoms after the COVID-19 infection? And if so, which symptoms? To this new information, we link data that were collected in the past by fellow researchers during the initial infection. That is to say, we collected the data when these people were still in the hospital or IC ward or whether or not they had rehabilitated in a rehabilitation centre. That old data concerns blood values, ECG films, lung tests, et cetera. Perhaps we can find a correlation with certain Long COVID symptoms.’

Sander: ‘Two of the seven cohort studies are control cohorts for our study. These are the POPCORN study and the Queen of Hearts study. The POPCORN study investigated a cross-section of the population during the first COVID-19 wave. At that time, the vast majority of the participants in this study were not infected. Queen of Hearts – a study by Chahinda – is not about COVID-19 but about the relationship between problems during pregnancy and long-term cardiovascular problems. Also, via this study, we collected data from people who were not or who were only moderately ill after a COVID-19 infection.

Chahinda: ‘The Long COVID study teaches us a lot about post-viral syndromes in general. Thanks to the control cohort, we can investigate to what extent symptoms after a COVID-19 infection are related to the inflammation itself or to one of the societal and social changes during the pandemic, such as quarantine measures, lockdowns and the curfew. Perhaps we can also find people in the control groups of symptoms of fatigue or with fitness problems even though they did not experience a COVID-19 infection. The control cohorts tell us something about the consequences of the corona measures.’

Sander: ‘We have now collected a lot of data. We will use this to answer the most urgent questions about Long COVID. For example, we will examine whether we can explain the development of Long COVID, and can predict who will develop it. With a bit of luck, we will be able to find correlations between Long COVID in certain disease processes. Then you can work on managing expectations. These will not be causal correlations and, therefore, not one-to-one relationships. We need to conduct follow-up research to establish causal relationships.’

Chahinda: ‘However, we can say whether our hypotheses are plausible and then build further upon these in the follow-up research. For example, imagine we find people with shortness of breath symptoms or chest pain correlated with high enzyme levels during hospital admission. This then gives rise to a hypothesis: should we, in future, conduct an MRI or ultrasound in such cases? Should we investigate whether the cause lies in the coronary vessels, or in an inflammation of the pericardium?’

Chahinda: ‘The pandemic is now behind us. However, that does not make research into Long COVID less relevant. For example, there are still people who suffer from lingering symptoms after an influenza infection or another viral lung infection. The Long COVID study teaches us a lot about post-viral syndromes in general. That is why we find follow-up research so important. Participants in our study still feel involved at the moment. But that might be different in a year’s time. Therefore, now is the moment to take action.’

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