Understanding long-COVID is an ongoing endeavor, but defining the condition would provide a solid foundation
In the wake of COVID-19, millions of once-infected individuals are still feeling its effects. Post-acute sequelae of SARS-CoV-2 (PASC) – or, more succinctly named, long-COVID – is classed as ongoing, relapsing, or newly arising symptoms that persist for more than 30 days after SARS-CoV-2 infection. PASC is a significant concern to public health, yet deciding on a specific and clear definition has proved difficult, with studies focusing on individual symptoms, lacking an uninfected control group, and relying on retrospective design. The heterogeneous nature of PASC further complicates matters; moreover, its symptoms can resemble conditions with other etiologies.
Recognizing this gap, researchers have conducted a longitudinal, prospective study to define PASC using self-reported symptoms from both infected patients and uninfected controls (1). Using data from 9,764 participants in the RECOVER adult cohort, they first developed a scoring framework to define PASC as a condition specific to SARS-CoV-2, and identified 37 symptoms that were present more frequently in SARS-CoV-2-infected participants six months post-infection compared with their uninfected counterparts. Symptoms that contributed to PASC score included post-exertional malaise, fatigue, brain fog, chronic cough, gastrointestinal symptoms, among others.
Ten percent of participants infected with COVID-19 after December 1, 2021, and enrolled within 30 days of infection were found to experience PASC six months later. PASC was more common and more severe in individuals infected before the emergence of Omicron, which supports previous research showing an association between PASC and earlier COVID-19 variants (2). Higher PASC scores were also associated with a decline in wellbeing and functioning.
Overall, the research moves us one step further toward defining PASC as a distinct condition specific to SARS-CoV-2; however, it is not without its limitations. The authors highlight that participants in the uninfected group could have had asymptomatic SARS-CoV-2 in the past that wasn’t detected “due to variations in antibody production and persistence, weakening the discriminant characteristics of this PASC score threshold.” They also recognize that over 200 symptoms of PASC have previously been reported – all of which may significantly impact quality of life.
T Thaweethai et al., “Development of a Definition of Postacute Sequelae of SARS-CoV-2 Infection,” JAMA, 329, 1934 (2023). PMID: 37278994.
ZA Sherif et al., “Pathogenic mechanisms of post-acute sequelae of SARS-CoV-2 infection (PASC),” Elife, 12, e86002 (2023). PMID: 36947108.