Clot Risk More Common in Survivors of Severe COVID Versus Flu

The burden of post-acute medical and mental health conditions among those who had been hospitalized for COVID-19 was mostly comparable to those who had been hospitalized for influenza and sepsis, with one difference, a population-based cohort study from Canada showed.

Among nearly 380,000 patients, hospitalization for COVID was associated with an increased 1-year risk of venous thromboembolism (VTE) compared with influenza (adjusted HR 1.77, 95% CI 1.36-2.31), reported Kieran Quinn, MD, PhD, of the Sinai Health and University Health Network in Toronto, and colleagues.

There were no other increased risks of selected ischemic and non-ischemic cerebrovascular and cardiovascular disorders, neurological disorders, rheumatoid arthritis, or mental health conditions compared with the influenza or sepsis groups, they noted in JAMA Internal Medicine.

"It is important to note that a higher proportion of people hospitalized for COVID-19 died during hospitalization compared with influenza or sepsis, which influences the risk profile of survivors and may explain why the risks of many outcomes were lower among survivors of COVID-19 hospitalization compared with influenza or sepsis," Quinn and colleagues wrote.

"Overall, the comparable rates of serious medical and mental health conditions following hospitalization for COVID-19, influenza, or sepsis suggest that many of these conditions may be related to the severity of illness from any infection that necessitated hospitalization, rather than being direct consequences of infection with SARS-CoV-2," they added.

These findings differ from previous research showing that COVID was linked to increased risks of long-term health outcomes. "These associations may have been overestimated due to the choice of comparator groups in some studies," the researchers noted.

Previous studies compared hospitalization for COVID versus hospitalization for any cause "which would include a broad range of diagnoses (including elective surgical procedures) and varying severity of illness, limiting comparability," they wrote.

A large study from Sweden demonstrated a similar association between COVID and thrombotic events, but another study showed no increase in overall risk for VTE among outpatients, though higher rates were seen for certain subgroups, including those with a prior VTE, those with primary or secondary thrombophilia, and those ages 75-84.

"This study advances the understanding of the long-term sequelae of COVID-19 by disentangling the outcomes of hospitalization for acute and critical illness from pathological features specific to COVID-19," Quinn and team wrote. "These observations do not diminish the effects of PCC [post-COVID condition, or long COVID] on populations and health systems around the world, given the large number of people hospitalized for COVID-19 who have experienced severe mortality and substantial long-term morbidity."

"At a health system and policy level, it is important to recognize the long-term consequences of severe infectious illnesses, including COVID-19, influenza, and sepsis, and invest in longitudinal care to support people beyond their immediate discharge from hospital," they added.

For this study, Quinn and colleagues included all adults hospitalized for COVID from April 2020 through October 2021 (n=26,499), historical comparator groups hospitalized for influenza or sepsis (n=299,989), and a contemporary comparator group hospitalized for sepsis in Ontario (n=52,878).

The overall cohort had a median age of 75, and 54% were women. Those in the COVID group were generally younger (median age 61) and less likely to be women (46.4%). Seven percent of the COVID group were partially or fully vaccinated.

Quinn and team noted that their study was limited to patients who survived hospitalization for COVID, and was mostly composed of older adults. Furthermore, findings may not be generalizable to outpatient settings, since testing for COVID and influenza is less systematic.

The study's results are also not generalizable to current virus strains.

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