Eight months after mild COVID-19, one in ten people experience at least one moderate to severe symptom that is perceived to have a negative impact on their work, social or personal life, according to a study.
The study, published in the journal JAMA, found that the most common long-term symptoms are loss of smell and taste, and fatigue.
Researchers at Danderyd Hospital and Karolinska Institutet in Sweden have been conducting the so-called COMMUNITY study since spring last year, with the main purpose of examining immunity after COVID-19.
"We investigated the presence of long-term symptoms after mild COVID-19 in a relatively young and healthy group of working individuals, and we found that the predominant long-term symptoms are loss of smell and taste," said Charlotte Thalin, lead researcher for the COMMUNITY study at Danderyd Hospital and Karolinska Institutet.
"Fatigue and respiratory problems are also more common among participants who have had COVID-19 but do not occur to the same extent," Thalin said.
In the first phase of the study, blood samples were collected from 2,149 employees at Danderyd Hospital, of whom about 19 per cent had antibodies against SARS-CoV-2.
The researchers collected blood samples every four months, and study participants responded to questionnaires regarding long-term symptoms and their impact on the quality of life.
In the third follow-up in January this year, the team examined self-reported presence of long-term symptoms and their impact on work, social and home life for participants who had had mild COVID-19 at least eight months earlier.
This group consisted of 323 healthcare workers — 83 per cent women with a median age 43 years — and was compared with 1,072 healthcare workers comprising 86 per cent women with a median age 47 years who did not have COVID-19 throughout the study period.
The results show that 26 per cent of those who had COVID-19 previously, compared to nine per cent in the control group, had at least one moderate to severe symptom that lasted more than two months.
About 11 per cent, compared to 2 per cent in the control group, had a minimum of one symptom with negative impact on work, social or home life that lasted at least eight months, according to the researchers.
The most common long-term symptoms were loss of smell and taste, fatigue, and respiratory problems, they said.
However, the researchers did not see an increased prevalence of cognitive symptoms such as brain fatigue, memory and concentration problems or physical disorders such as muscle and joint pain, heart palpitations or long-term fever.
Despite the fact that the study participants had a mild COVID-19 infection, a relatively large proportion report long-term symptoms with an impact on quality of life, they said.
"In light of this, we believe that young and healthy individuals, as well as other groups in society, should have great respect for the virus that seems to be able to significantly impair quality of life, even for a long time after the infection," said Sebastian Havervall, a PhD student in the project at Karolinska Institutet.
The researchers said that the COMMUNITY study will continue, with the next follow-up taking place in May when a large proportion of study participants are expected to be vaccinated.