Long COVID is not a single condition, study finds

Long COVID is not a single condition, and should not be treated as such, according to new data collected in nationwide study released May 31 in the Open Forum of Infectious Diseases.

The study looked at persistent symptoms experienced by patients with COVID-19 both at three- and six-month intervals. In all, 5,963 patients participated in the study, with 4,504 of the participants testing positive for COVID-19 and 1,459 testing negative. Many of the participants, 2,000 in all, came from King County through the University of Washington School of Medicine.

The four major symptom categories for people who tested positive for COVID-19 included:

• Minimal symptoms (72% of the cases)
• Tiredness, headache and muscle/joint aches (17% of cases)
• Tiredness, headache and muscle/joint aches with loss of taste and smell (5% of cases)
• Symptoms across multiple systems (6% of cases)

This study is clinically significant because it shows how the long-term symptoms from the virus changes its presentation over time, noted Kari Stephens, senior author and the Helen D. Cohen Endowed Professor and research section head in  the Department of Family Medicine and an adjunct professor in the Department of Biomedical Informatics and Medical Education at the University of Washington School of Medicine.

Most long COVID studies have focused primarily on the individual symptoms without considering clusters or patterns of symptoms. Many did not have comparison groups and focused only on data captured by providers during clinic visits, rather than directly from patients, she said.

“This study also gives providers information about how long-term outcomes for COVID may look and present in patients over time,” she said. “This study will help us understand how we need to treat long COVID over time, in very specific ways for each patient depending on how their symptoms present.”

This study is unique in that people were able to report symptoms directly, regardless of whether or not they received medical care.

 “While it is becoming increasingly clear that long COVID is not a singular condition, having data showing several distinct, symptom-defined phenotypes is a strong step towards developing evidence-driven approaches to treat the millions of people who continue to experience lingering symptoms,” said Michael Gottlieb, vice chair of research for emergency medicine at Rush University Medical Center and lead author.

Overall, the study will help determine funding and policy support for long COVID programs, Stephens added.

“We don’t want to forget about long COVID as we all go back to “normal,”” Stephens said. “New long COVID cases are occurring every day.”

Currently the CDC estimates that 11% of those who contracted COVID-19 are now experiencing symptoms of long COVID.

The nearly 6,000 participants began self-reporting symptom data via detailed surveys beginning in December 2020 and were followed for up to 18 months. This part of the study concluded in September 2022.

INSPIRE, or Innovative Support for Patients with SARS-CoV-2 Infections, is a federally funded collaboration of eight major academic medical centers, including UW Medicine, seeking to better understand the long-term effects of COVID. The patients were recruited from eight major health organizations and self-reported their symptoms in a standardized questionnaire. The INSPIRE group has been studying COVID since the first documented U.S. case  was found just outside the Seattle area in January 2020. This is the sixth study released by the group.

This work was supported by the Centers for Disease Control and Prevention, National Center of Immunization and Respiratory Diseases (NCIRD) (contract number: 75D30120C08008; PI: Robert A. Weinstein). Partners from the CDC, Ian D Plumb Sharon Saydah, assisted with study design and the preparation of the research manuscript.