A large study released today suggests that people who experience worse COVID-19 symptoms may be more likely to subsequently develop notable symptoms 12 weeks or more after the initial infection. Also, most patients went on to have long COVID, regardless of the severity of their original illness.
The study, published by the European Centre for Disease Prevention and Control (ECDC), was based on data collected on pre-Omicron infections. A total of 61 cohort studies from 15 countries were included in the analysis, which included 74,213 post–COVID-19 cases that had been assessed at least 12 weeks after infection in the European Union (EU)/European Economic Area (EEA), the United Kingdom, United States, Canada, Australia, and New Zealand.
The systematic review and meta-analysis estimated the prevalence of symptoms of post COVID-19 condition, stratified by recruitment setting (community, hospital, and intensive care unit [ICU]) as a proxy for disease severity.
Five post–COVID-19 symptoms—fatigue, shortness of breath, depression, headache, and dizziness—were noted to be more prevalent in patients from hospital settings than community settings, suggesting that severity of disease is a factor in determining who is at risk for developing long COVID.
Long COVID in 51% to 74% of patients
Overall, the authors found very high rates of post-COVID symptoms: The prevalence of any post–COVID-19 condition symptom was estimated at 50.6% (95% confidence interval [CI], 41.1% to 60.2%) among cohorts recruited in the community setting; 66.5% (95% CI, 56.0% to 76.3%) among cohorts recruited in the hospital setting; and 73.8% (95% CI, 62.3% to 83.9%) among cohorts recruited in the ICU setting.
Patients in community settings most often reported at 12 or more weeks an impact on quality of life (36.9%), general weakness (31.3%), fatigue (30.8%), shortness of breath (20.9%), depression (17.3%), concentration problems (15.6%), headache (14.4%), dizziness (10.2%), and body aches (10.0%).
For patients who were hospitalized, the most common symptoms seen after 12 weeks included fatigue (46.1%), shortness of breath (45.4%), depression (23.3%), hair loss (22.1%), and joint pain (20.0%).
Symptoms were not assessed for ICU patients.
'Still many unknowns'
The report shows a much higher prevalence of long COVID symptoms in both community and hospital setting patients than found in earlier studies. Various studies from Europe and the United States estimate long COVID to affect 1 in 5 to 1 in 8 patients.
"Symptom prevalence estimates reported here must be interpreted with caution as the majority of the included studies lack non-infected comparator groups. Absence of a non-infected comparator group may lead to overestimation of those symptoms attributed to prior SARS-CoV-2 infection," the authors wrote.
Regardless, this is one of the largest studies to examine risk factors and disease severity in relation to the development of long COVID.
"There are still many unknowns, in terms of current and future risks to populations for post COVID-19 condition in the context of increased levels of vaccination and hybrid immunity," the ECDC said in a press release on the report.
"Looking ahead, additional large-scale population-based studies with appropriate control groups are required to assess which long-term symptoms are specifically attributable to SARS-CoV-2 infection and their association with a wide range of demographic and clinical risk factors."