In a recent study published in Research Square *, researchers evaluated the long-term sequelae of coronavirus disease 2019 (COVID-19) in Scotland.
Study: Long-COVID study in Scotland: a nationwide population cohort study. Image Credit: RoundGlobalMaps / Shutterstock
Although most patients fully recover from COVID-19 caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), some experience COVID-19 for a long time. The World Health Organization has long defined COVID-19 in those with a history of COVID-19 as the persistence of symptoms for two months or more, with no explanation for any alternative diagnosis. This inaccuracy reflects a lack of a comprehensive understanding of the nature of the condition and the underlying mechanisms.
About the study
In the current study, researchers looked at long-term COVID in the general public in Scotland. The Long COVID in Scotland (Long-CISS) study is an ambidirectional cohort study. Scots aged 16 and over were eligible for a positive polymerase chain reaction (PCR) test for COVID-19 between April 2020 and May 2021.
In addition, a matched control group of SARS-CoV-2 PCR-negative individuals was established. Participants completed an online questionnaire that captured data on pre-existing comorbidities in the index test (first positive test or last negative test in the case of controls), current symptoms, quality of life, and limitations on daily activities. Respondents completed three questionnaires in the 6-, 12-, and 18-month post-index tests.
COVID-19 infection was defined as a positive result of the PCR test recorded in the national database and subjects were stratified into symptomatic or asymptomatic categories as reported by respondents. Severe illness was defined as admission to a hospital with code U07.1 of the Tenth Revision of the International Classification of Diseases (ICD-10). The excluded were respondents who reported the positive status of the PCR but were not registered in the national database.
Respiratory disease, depression, coronary heart disease, and diabetes were defined by ICD-10 codes or self-reports. The results of the study were 26 symptoms, quality of life, limitations in seven daily activities, hospitalization, admission to the intensive care unit (ICU), all-cause mortality, and recovery status (for symptomatic cases).
Discoveries
Of the 638,125 people invited to the study, 16% (102,473) participated. The final cohort consisted of 96,238 subjects. The median age was 45 years; men made up 39% of the cohort and 91% of participants were white. At least one pre-existing comorbidity was observed in 30% of respondents and 4% were vaccinated with at least one dose before the index test.
About 95% of the 33,281 SARS-CoV-2-positive respondents were symptomatic. Most people (82%) had three symptoms. During the acute infection phase, 83% of subjects reported fatigue, 64% reported headache, and 63% had myalgia. All participants completed the first questionnaire (six months later), 20% completed the second questionnaire, and only 809 respondents completed the final survey.
About 42% of symptomatic cases reported partial recovery at the most recent follow-up and 6% did not recover. Symptoms persisted in 21,525 subjects after symptomatic COVID-19, and the most common were headache, fatigue, muscle aches, or weakness. After adjusting for possible confounding factors, people with the above symptomatic disease were more likely to report 24 symptoms (out of 26) at follow-up.
Lack of recovery after symptomatic illness was associated with severe clinical course (hospitalization), deprivation, old age, female sex, and pre-existing comorbidities, including respiratory illness and depression. People with a previous symptomatic infection did not show a significant increase in the risk of hospitalization, ICU admission, or death.
After adjusting for possible confounding factors, people with symptomatic COVID-19 were more likely to report impaired activities of daily living (mobility, work, exercise, and relationships). Asymptomatic disease was not associated with an increased risk of current symptoms, impairment of daily activities, hospitalization, or all-cause mortality. In their most recent follow-up, those vaccinated before symptomatic illness were less likely to have a persistent change in smell / taste, hearing problems, confusion or difficulty concentrating, and depression / anxiety.
Conclusions
The researchers noted that nearly half of those infected had not recovered or only partially recovered after 6 to 18 months of symptomatic COVID-19. Symptomatic illness was associated with many persistent symptoms, reduced quality of life, altered daily activities, regardless of sociodemographic factors, and comorbidities.
There was no evidence of persistent sequelae after asymptomatic disease. The strongest association for persistent symptoms was observed for cardiovascular symptoms such as chest pain, shortness of breath, palpitations, and confusion. In addition, the authors found that serious illness, female gender, old age, pre-existing respiratory illness, and deprivation were associated with lack of recovery.
However, pre-infection vaccination reduced the risk of seven persistent symptoms. Overall, the results indicated that after 6 to 18 months of symptomatic SARS-CoV-2 infection, adults were more likely to experience a wide range of symptoms, with a lower quality of life and impaired daily life, which was not explained by confusion.
* Important news
Research Square publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guided by clinical practice or health-related behavior, or treated as established information.