Nearly half of people infected with COVID-19 experienced some 'long COVID' symptoms, study finds

Around the world, 43 percent of those infected with COVID-19 experienced post-COVID conditions, according to a new analysis by University of Michigan School of Public Health that looked at data from 50 studies and 1.6 million people.

"I was really surprised to see the results of this meta analysis, and in particular that fatigue and memory problems were the two most commonly reported post-COVID conditions," said Bhramar Mukherjee, the John D. Kalbfleisch Collegiate Professor and Chair of Biostatistics at the U-M School of Public Health and senior author of the study, published this week in the Journal of Infectious Disease.

The World Health Organization offered a clinical case definition of post-COVID conditions in October 2021 as mid- and long-term symptoms occurring in individuals after COVID-19 infection, also known as long COVID.

Mukherjee and the team studied the prevalence of this condition globally and regionally, estimating the proportion of individuals facing long COVID in Asia, Europe and North America.

Highlights from the study include:

• Global prevalence for post-COVID-19 conditions at 30, 60, 90 and 120 days after infection were estimated to be 37, 25, 32, and 49 percent.
• Regionally, Asia had the highest post-COVID-19 condition prevalence at 51 percent, followed by Europe at 44 percent, and North America at 31 percent.
• Fatigue (23 percent) and memory problems (14 percent) were cited as the most common symptoms of individuals with post-COVID-19 condition.
• Some lingering post-COVID-19 symptoms remain in roughly 34 percent of non-hospitalized COVID patients while the rate jumps to 54 percent for hospitalized COVID patients.

The researchers suggest that the changing landscape of COVID-19 due to new variants may have implications for prevalence of long COVID and symptom burden in the future, highlighting the Omicron variant's milder symptoms on vaccinated and previously infected populations. They also point out that different protocols in long COVID diagnosis across the world make it challenging to synthesize studies.

Chen Chen and Spencer Haupert, lead authors of the study, and graduate students in biostatistics note that understanding the risk factors for long COVID will better prepare healthcare providers and systems to develop post COVID management plans.

"Long COVID is quite common overall and across geographic regions, sex and acute COVID-19 severity. Knowing this, providers should take proactive approaches such that their patients are well-supported when experiencing long-term health effects of COVID-19," they wrote.

In addition to Mukherjee, Chen, and Haupert, Lauren Zimmermann, Xu Shi, and Lars Fritsche—all of U-M's School of Public Health—were involved in the study.