Study IDs Most Common Lingering Symptoms 8 Months After Mild COVID

Damian McNamara

April 09, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Loss of smell, loss of taste, dyspnea, and fatigue are the four most common symptoms that healthcare professionals in Sweden report 8 months after mild COVID-19 illness, new evidence reveals.

Approximately one in 10 healthcare workers experience one or more moderate-to-severe symptoms that negatively affect their quality of life, according to the study.

Dr Charlotte Thålin

"We see that a substantial portion of healthcare workers suffer from long-term symptoms after mild COVID-19," senior author Charlotte Thålin, MD, PhD, told Medscape Medical News. She added that loss of smell and taste "may seem trivial, but have a negative impact on work, social, and home life in the long run."

The study is noteworthy not only for tracking the COVID-19-related experiences of healthcare workers over time, but also for what it did not find. There was no increased prevalence of cognitive issues — including memory or concentration — that others have linked to what's often called long-haul COVID-19.

The Research Letter was published online April 7, 2021, in JAMA.

"Even if you are young and previously healthy, a mild COVID-19 infection may result in long-term consequences," said Thålin, from the department of clinical sciences at Danderyd Hospital, Karolinska Institute, Stockholm, Sweden.

The researchers did not observe an increased risk for long-term symptoms after asymptomatic COVID-19.

Adding to Existing Evidence

This research letter "adds to the growing body of literature showing that people recovering from COVID have reported a diverse array of symptoms lasting for months after initial infection," Lekshmi Santhosh, MD, told Medscape Medical News when asked to comment. She is physician faculty lead at the University of California, San Francisco (UCSF) Post-COVID OPTIMAL Clinic.

Dr Lekshmi Santhosh

Previous research revealed severe long-term symptoms, including heart palpitations and neurologic impairments, among people hospitalized with COVID-19. However, "there is limited data on the long-term effects after mild COVID-19, and these studies are often hampered by selection bias and without proper control groups," Thålin said.

The absence of these more severe symptoms after mild COVID-19 is "reassuring," she added.  

The current findings are part of the ongoing COMMUNITY (COVID-19 Biomarker and Immunity) study looking at long-term immunity. Healthcare professionals enrolled in the research between April 15 and May 8, 2020, and have initial blood tests repeated every 4 months.

Thålin, lead author Sebastian Havervall, MD, and their colleagues compared symptom reporting between 323 hospital employees who had mild COVID-19 at least 8 months earlier with 1072 employees who did not have COVID-19 throughout the study.

The results show that 26% of those who had COVID-19 previously had at least one moderate-to-severe symptom that lasted more than 2 months, compared with 9% in the control group.

The group with a history of mild COVID-19 was a median 43 years old and 83% were women. The controls were a median 47 years old and 86% were women.

Dr Sarah Jolley

"These data mirror what we have seen across long-term cohorts of patients with COVID-19 infection. Notably, mild illness among previously healthy individuals may be associated with long-term persistent symptoms," Sarah Jolley, MD, a pulmonologist specializing in critical care at UCHealth University of Colorado Hospital in Aurora and director of the Post-COVID Clinic, told Medscape Medical News.

"In this cohort, similar to others, this seems to be more pronounced in women," Jolley added.

Key Findings on Functioning

At 8 months, using a smartphone app, participants reported presence, duration, and severity of 23 predefined symptoms. Researchers used the Sheehan Disability Scale to gauge functional impairment.

A total of 11% participants reported at least one symptom that negatively affected work or social or home life at 8 months vs only 2% of the control group.

Seropositive participants were almost two times more likely to report that their long-term symptoms moderately to markedly disrupted their work life, 8% vs 4% of seronegative healthcare workers (relative risk [RR], 1.8; 95%; confidence interval [CI], 1.2 - 2.9).

Disruptions to a social life from long-term symptoms were 2.5 times more likely in the seropositive group. A total 15% of this cohort reported moderate-to-marked effects, compared with 6% of the seronegative group (RR, 2.5; 95% CI, 1.8 - 3.6).

The researchers also inquired about home life disruptions, which were reported by 12% of the seropositive healthcare workers and 5% of the seronegative participants (RR, 2.3; 95% CI, 1.6 - 3.4).

The study's findings "tracks with a lot of the other work we're seeing," David Putrino, PT, PhD, director of rehabilitation innovation at Mount Sinai Health System in New York City, told Medscape Medical News. He and his colleagues are responsible for managing the rehabilitation of patients with long COVID.

Dr David Putrino

Interestingly, the proportion of people with persistent symptoms might be underestimated in this research, Putrino said. "Antibodies are not an entirely reliable biomarker. So what the researchers are using here is the most conservative measure of who may have had the virus."

Potential recall bias and the subjective rating of symptoms were possible limitations of the study.

When asked to speculate why researchers did not find higher levels of cognitive dysfunction, Putrino said that self-reports are generally less reliable than measures like MoCA (Montreal Cognitive Assessment) for detecting cognitive impairment.

Furthermore, unlike many of the people with long-haul COVID-19 whom he treats clinically — ones who are "really struggling" — the healthcare workers studied in Sweden are functioning well enough to perform their duties at the hospital, so the study population may not represent the population at large.

More Research Required

"More research needs to be conducted to investigate the mechanisms underlying these persistent symptoms, and several centers, including UCSF, are conducting research into why this might be," Santhosh said.

Thålin and colleagues plan to continue following participants. "The primary aim of the COMMUNITY study is to investigate long-term immunity after COVID-19, but we will also look into possible underlying pathophysiological mechanisms behind COVID-19-related long-term symptoms," she said.

"I hope to see that taste and smell will return," Thålin added.

"We're really just starting to understand the long-term effects of COVID-19," Putrino said. "This is something we're going to see a lot of moving forward."

Thålin, Santhosh, Jolley, and Putrino disclosed no relevant financial relationships. Grants from the Knut and Alice Wallenberg Foundation, Jonas and Christina af Jochnick Foundation, Leif Lundblad Family Foundation, Region Stockholm, and Erling-Persson Family Foundation funded the research.

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter: @MedReporter.

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