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Nurses close the curtains of a patient's room in the Intensive Care Unit at Surrey Memorial Hospital in Surrey, B.C., on June 4, 2021.JONATHAN HAYWARD/The Canadian Press

People have heightened risks of developing serious conditions, such as heart failure, dementia and depression, within a year of being hospitalized for COVID-19, similar to those who survive hospitalization for other infectious diseases, like influenza and sepsis, Ontario researchers have found.

In a study, published on Tuesday in JAMA Internal Medicine, the researchers said many of these long-term health outcomes may be related to the severity of patients’ illnesses, rather than a direct consequence of COVID-19 itself.

These findings suggest people require substantial care after they are hospitalized for COVID-19 and other serious infectious diseases, and that the health care system needs to consider how it can better provide that care, particularly to older adults with multiple health conditions, said Toronto clinician-scientist Kieran Quinn, lead author of the study and assistant professor in the University of Toronto’s department of medicine.

“These aftereffects of hospitalization, in general, stand to have a substantial and lasting impact on people and our health care system,” Dr. Quinn said.

He added that the results of the study “reinforce that COVID is – and the aftereffects are – severe, but so are many other health conditions.”

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Before seasonal flu patterns were disrupted during the pandemic, influenza caused an estimated 12,200 hospitalizations and 3,500 deaths a year in Canada, with many of those deaths occurring among residents of long-term care.

Patients with COVID-19 logged more than 125,900 hospital stays in Canada between April, 2021, and March, 2022, according to the Canadian Institute for Health Information. The latest federal data show they currently occupy about 2,000 hospital beds per week.

The study analyzed the health data of more than 379,000 adults in Ontario. It compared those who were hospitalized for COVID-19 between April, 2020, and October, 2021, with patients who were hospitalized with influenza before start of the pandemic, and those hospitalized with sepsis, a blood infection, both before and after the start of the pandemic.

COVID-19 was associated with a higher risk of venous thromboembolism, or blood clots, stroke and depression or anxiety within the first 30 days of leaving hospital, the study said. These risks appeared to dissipate after 30 days, it said. Aside from this, it found people hospitalized with COVID-19 did not have a greater risk of developing other new cardiovascular, neurologic or mental-health conditions than their counterparts who were hospitalized with flu or sepsis.

Dr. Quinn said the rates of these conditions, however, are about two to five times higher among people who have survived hospitalization for serious infections than the rest of the population. This is likely because these infections can trigger an overwhelming inflammatory response, which can lead to damage to various organs throughout the body, he said. He emphasized the need to take measures, including vaccination, to prevent serious illness from infections.

Nitin Mohan, an assistant professor in the department of microbiology and immunology at Western University, who was not involved in the study, said the findings are helpful for understanding the health care resources that will be needed to prepare for the long-term effects of COVID-19. He said he hoped to see further studies.

“As we gather more data, as more time passes, we learn more about this virus and how to prepare for it,” Dr. Mohan said.

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