Long COVID: A narrative review and meta-analysis of individual symptom frequencies

This RECOVER study looked at how common 21 Long COVID symptoms were in adults before the Omicron wave of the COVID-19 pandemic. Researchers started by looking at 59 research papers. They then rated each paper based on information bias, which means how much the findings reported in the paper might have been affected by how the study was conducted or who participated in the study. Papers with less bias originated from studies that looked at groups of participants who represented the general population in a country, received survey responses from most participants, and included a comparison group of people who never had COVID. 

Researchers found that the number of Long COVID symptoms people reported was different depending on how the study collected that information. For example, when people filled out surveys about their symptoms, about one in four people reported Long COVID symptoms like feeling very tired or having trouble breathing. But in studies using electronic health records (EHRs), fewer than one in thirteen people had Long COVID symptoms. This shows that many people may have had Long COVID symptoms that they did not report to their doctor. 

This study is important because it shows that more people may have had Long COVID earlier in the pandemic than researchers thought. Future research should focus on grouping symptoms into clear patterns so doctors can better recognize Long COVID and choose the right treatment for people experiencing its symptoms.