A new study indicates that a significant portion of the recognized COVID-19 'sequelae' may be linked to other factors. Scientists have found that traditional approaches to assessing long-term effects may mistakenly attribute to the coronavirus health problems that arose for other reasons.
How the approach to assessing sequelae has changed
The researchers applied a new approach that identified 98% fewer sequelae in the period from 4 to 12 months after infection. It is important to note that this does not mean long COVID occurs 98% less often; the result merely demonstrates how strongly conclusions depend on the study's methodology.
Analysis methodology
For the analysis, the scientists examined 14.4 billion medical records belonging to more than 244 million US residents. The work used the synthetic control method, which is borrowed from the fields of economics and social sciences and helps more accurately match groups of participants while accounting for their differences.
Unlike previous studies, in which people with a positive COVID-19 test were compared with those who were not diagnosed with the infection (a group that could also include people who were never tested at all), the new method compared only patients who took a PCR test for the coronavirus for the first time. This made it possible to reduce the influence of differences in participants' behavior and health status before testing.
Key finding
Thus, the analysis emphasizes that when assessing sequelae it is important to take the study design into account in order to avoid a false link between the coronavirus and health problems that arose for other reasons.
