Aug. 5, 2022 -- One in eight adults diagnosed with COVID-19 will likely experience long-term symptoms, a large study published this week shows.

To reach that conclusion, the researchers compared long-term symptoms in people infected by SARS-CoV-2, the coronavirus that causes COVID-19, with similar symptoms in uninfected people over the same time period.

Among the group of infected study participants in the Netherlands, 21.4% had at least one new or severely increased symptom 3 to 5 months after infection compared to before infection. When that 21.4% was compared to 8.7% of uninfected people in the same study, the researchers were able to calculate that 12.7% of the patients experienced long COVID.

“This finding shows that post-COVID-19 condition is an urgent problem with a mounting human toll,” the study authors write.

Christopher Brightling and Rachael Evans, PhD, of the Institute for Lung Health, University of Leicester in the United Kingdom, who were not involved in the study, said in a separate editorial, “This is a major advance on prior long COVID … estimates as it includes a matched uninfected group and accounts for symptoms before COVID-19 infection.”

Symptoms That Persist

The study, published in the journal The Lancet, finds that 3 to 5 months after COVID-19 the symptoms that persisted were chest pain, breathing difficulties, pain when breathing, muscle pain, loss of taste and/or smell, tingling in the hands or feet, lump in throat, feeling hot and cold alternately, heavy limbs, and tiredness.

Researcher Aranka V. Ballering, MSc, says they found fever was clearly present during the acute phase of the disease and it peaks the day of the COVID-19 diagnosis, but also wears off.

Loss of taste and smell, however, rapidly increases in severity when COVID-19 is diagnosed, but also persists and is still present 3 to 5 months after recovery from the virus.

Ballering, with the Department of Psychiatry at University of Groningen in the Netherlands, says she was surprised by the differences found between men and women in their research: “Women showed more severe persistent symptoms than men,” Ballering says.

Closer to a Clearer Definition

The authors say their findings also pinpoint symptoms that bring us closer to a better definition of long COVID, which has many different definitions globally.

Researchers collected data by asking participants in the northern-Netherlands, who were part of the population-based Lifelines COVID-19 study, to regularly complete digital questionnaires on 23 symptoms commonly associated with long COVID. The questionnaire was sent out 24 times to the same people between March 2020 and August 2021. At that time, people had the alpha or earlier variants.

Participants were considered COVID-19 positive if they had either a positive test or a doctor’s diagnosis of COVID-19.

Effect of Hospitalization, Vaccination Unclear

Ballering says it’s unclear from this data whether vaccination or whether a person was hospitalized would change the outcomes in patients.

Because when the data was collected, “the vast majority of our study population was not fully vaccinated,” she says.

However, she points to recent research that shows that vaccination against COVID -19is only partially effective against persistent symptoms after infection.

Also, only 5% of men and 2.5% of women in the study were hospitalized due to COVID-19 so the findings can’t easily be generalized to hospitalized patients.

Janko Nikolich-Žugich, MD, PhD, head of the Immunobiology Department at University of Arizona College of Medicine in Tucson, says he agrees that a primary benefit of this study is that it corrected for symptoms people had before COVID-19, something other studies have not been able to do.

However, he warns against generalizing the results for the United States and other countries because of the lack of diversity in the study population. He says access issues are also different in the Netherlands, which has universal health care.