Design by Maggie Weibe

U-M study finds severe COVID-19 illness likely to be accompanied by long-haul symptoms

A new University of Michigan study, led by U-M School of Public Health research investigator Dr. Jana Hirschtick, found a higher prevalence of long-haul symptoms amongst individuals who had severe COVID-19 symptoms.

The study found that ‘long COVID’ was fairly common amongst COVID-19 survivors in the sample population, 53% of whom had symptoms persisting 30 days post-COVID-19 onset. More so, 35% of them were still experiencing symptoms 60 days post-onset. The measured value of the study, termed post-acute sequelae of SARS-CoV-2 (PASC), was operationally defined as COVID-19 symptoms that persist for a set number of days post COVID-19 onset and separated into two categories of either 30 or more days (30-day COVID-19) and 60 or more days (60-day COVID-19). The researchers used data from the Michigan COVID-19 Recovery Surveillance Study (MI CReSS), a program Dr. Hirschtick is a co-investigator for, resulting in a sample size of 593 Michigan adults aged 18 and older.  

In her release, Hirschtick explained that she and the team started their research shortly after the pandemic had started last year. Their main goal was to understand COVID-19 disparities in regard to illness severity and recovery. 

“We started early on in the pandemic, so we were not aware yet that people would have these prolonged courses of illness — what’s being (called) ‘long COVID’,” Hirschtick said. “And we also wanted to understand any inequities in COVID-19 illness and recovery, particularly by race, ethnicity, income.”

Infographic by Claire Yang

Hirschtick and colleagues also found that self-reported severe COVID-19 illness was associated with a 2.25 times higher prevalence of 30-day PASC and 1.71 times higher prevalence of 60-day PASC compared to mild self-reported illness. 

As for correlations between PASC and various predictors, the following conclusions were drawn by the researchers regarding income, age, hospitalization and psychological condition:

Infographic by Claire Yang

While autoimmune conditions, chronic obstructive pulmonary disease (COPD), and psychological conditions correlated with higher rates of PASC, researchers concluded that psychological condition was the only variable found to be statistically significant after adjustment. 

In an email to The Michigan Daily, Hirschtick wrote that although some hypotheses can be drawn about why these correlations exist, further research should be done.

“The link between a previously diagnosed psychological condition and PASC suggests that our current definition of PASC may be measuring several distinct syndromes with both physiologic and psychological components,” Hirschtick wrote. “We need to dig into this area further.”  

Respondents who had not yet recovered from COVID-19 for 60 or more days post viral onset mostly reported fatigue as their most persistent symptom. Other less common symptoms included shortness of breath, altered sense of taste or smell and muscle or joint pain.   

Although the study concluded a higher PASC prevalence in the older demographic, about 1 in 5 younger adults between the ages 18 to 35 were still experiencing symptoms after 60 days. Hirschtick explained the importance of these statistics, especially for the younger generation who are deciding whether or not to get vaccinated; more so, because people with mild COVID-19 illness reported experiencing long COVID-19.

“Individuals who are on the fence about vaccination should also be factoring PASC into the equation,” Hirschtick wrote. “Even young, healthy people are susceptible to PASC, so prevention is key.”

Hirschtick also said in the release that she hopes her study aids in the overall understanding of PASC and gives the medical community direction regarding treatment and management. 

“While we’re in the midst of trying to stop the spread of the pandemic, we need to develop formal, coordinated surveillance of long-term symptoms to better understand this syndrome and provide guidance for clinical management,” Hirschtick said. 

Daily Staff Reporter Nadir Al-Saidi can be reached at