LOS ANGELES – Since the start of the pandemic, patients and doctors have been frustrated by the significant minority of coronavirus infections that turn into long COVID, a bewildering collection of lingering and often disabling symptoms that linger for weeks, months or years after the initial infection subsides.
The condition has been reported in children and adults; in those with pre-existing conditions and those in good health; in patients hospitalized with COVID-19; and those who experienced only mild symptoms during their initial infection.
A new study by researchers at the University of Southern California offers insight into the prevalence of long-term COVID and suggests some early clues as to who might be more likely to develop long-term symptoms.
The study, published this month in Scientific Reports, also found that 23% of people who had coronavirus infections between March 2020 and March 2021 were still reporting symptoms up to 12 weeks later.
The researchers recruited about 8,000 people, some infected and some not, to answer bi-weekly questions about their general health and COVID-19 status. At the end of the one-year survey period, they had a sample of 308 people who had contracted the disease at some point during the year.
After filtering out respondents with symptoms like headaches and fatigue before infection due to unrelated conditions like seasonal allergies, the team found that nearly one in four people with COVID-19 was still struggling with symptoms 12 weeks after being infected.
“These people aren’t necessarily able to do all the activities they would like to do, not able to fully work and take care of their families,” said Eileen Crimmins, a demographer at USC’s Leonard Davis School of Gerontology. and co-author of the study.
Figuring out who is most at risk for a long time from COVID has proven a challenge for demographers and healthcare providers.
Several previous studies have identified women as being at greater risk. But the USC study found no relationship in its sample between long COVID and age, gender, race and pre-existing health conditions, including cancer, diabetes, hypertension and heart disease.
He noted a higher risk in patients who were obese before infection. And it also spotted some associations between the specific symptoms people experienced when first infected and the likelihood of developing long COVID. Patients who reported sore throats, headaches and, oddly, hair loss after testing positive were more likely to have persistent symptoms months later.
“Our hypothesis is that this hair loss reflects extreme stress, potentially a reaction to high fever or medication,” Crimmins said. “So that’s probably an indication of the severity of the disease.”
Because it only covered the first year of the pandemic, the study does not take into account two major developments: vaccines and variants. None of the COVID patients in the sample were eligible for vaccines during the study period, and all were infected before the UK’s Alpha variant reached US shores.
While the study’s 308 respondents were representative of the population, no snapshot of a few hundred people can tell the full story of the roughly 200 million people in the United States who have had the virus, according to Centers estimates. for Disease Control and Prevention.
“The authors made a commendable effort to identify factors associated with long COVID,” said Dr. Alain Lekoubou Looti, a neurologist at Penn State University who was not involved in the study. “However, these factors may need to be confirmed in larger samples.”
The most common long COVID symptoms reported were headache, nasal congestion, abdominal pain, fatigue and diarrhea. But the study didn’t address many of the symptoms that people living with long COVID describe as the most debilitating, said Hannah Davis, co-founder of the Patient-Led Research Collaborative, a research group that focuses on disease.
“We need work like this, but this work also indicates that they don’t know the duration of COVID very well,” Davis said. “The list of symptoms are primarily acute COVID symptoms and do not include the more common symptoms of post-exertional malaise, cognitive dysfunction, memory loss, sensory-motor symptoms and others.”
Defining long COVID presents a challenge for those trying to track or treat it. COVID-19 is a chimerical beast: symptoms evolve as the disease drags on and can vary widely from patient to patient.
The fluidity of long COVID makes it difficult to assess its prevalence. Various studies have placed the percentage of people reporting persistent symptoms 12 weeks after their initial infection between 3% and 50%.
“We need a universal case definition before we can truly understand the prevalence of long COVID. Right now, the definition varies wildly from study to study, resulting in a wide range of prevalence estimates,” said Jana Hirschtick, an epidemiologist at the University of Washington’s School of Public Health. Michigan. “After all this time, we still don’t have a clear idea of who is most at risk.”
The lack of strict diagnostic criteria is also a major problem for patients seeking treatment. At this time, long COVID is considered a “diagnosis of exclusion,” meaning a diagnosis that is only given after all other valid possibilities have been ruled out, said Melissa Pinto, associate professor of nursing at UC Irvine who studies the disease. In the United States, this can mean a long and expensive process of submitting to various tests and specialists.
For many longtime COVID patients, 12 weeks is just the beginning of an ordeal lasting months or years.
“I know people who have had this for 2 and a half years,” Pinto said. “There really isn’t a safety net for these people.”