ZURICH, Switzerland — More than one in six unvaccinated individuals who recovered from a confirmed bout of COVID-19 up to two years ago are still experiencing lingering health effects, according to researchers from the University of Zurich. In all, 17 percent of participants did not return to normal health and 18 percent reported COVID-19 related symptoms up to 24 months after their initial infection.
The majority of people who become infected with SARS-CoV-2 and develop COVID-19 recover soon after the initial phase of the disease. Others, however, deal with persistent, lingering symptoms for months or even years that can end up lowering one’s quality of life and ability to work. Dubbed “long COVID,” this phenomenon still isn’t entirely understood by scientists and doctors alike.
Previous research focused on longer term outcomes after COVID-19 infection, reporting a wide range of estimates (22-75% at 12-24 months), which stopped researchers from making any firm conclusions regarding long term treatment and support. So, in an effort to gain further clarity, study authors analyzed patterns of recovery and symptom persistence over two years among adults from the Zurich SARS-CoV-2 Cohort, an ongoing research project assessing individuals with confirmed SARS-CoV-2 infection.
These findings encompass 1,106 unvaccinated adults (average age 50) with a confirmed SARS-CoV-2 infection between August 2020 and January 2021, as well as 628 adults (average age 65) randomly selected from the general population who did not contract COVID.
Each person provided information on 23 potential long COVID symptoms at various follow-up points (6, 12, 18, and 24 months after infection). Study authors were also sure to account for other potentially influential factors like age, sex, education, employment, and pre-existing health problems.
In all, 55 percent of the participants reported seeing their health return to normal less than a month after infection, and another 18 percent reported recovery within one to three months. At the six-month mark, 23 percent of patients said they still hadn’t fully recovered. That figure declined to 19 percent at the 12-month point and 17 percent at 24 months.
Proportions of patients continuing to deal with symptoms thought to be related to COVID-19 at the three timepoints were very similar but also slightly higher, dropping from 29 percent at six months, to 20 percent at one year, and to 18 percent at two years. In comparison to those who did not have an infection, people with COVID-19 displayed excess risks for both physical problems, such as altered taste or smell (9.8%), malaise after exertion (9.4%), and shortness of breath (7.8%), as well as mental health issues including lower concentration (8.3%) and anxiety (4%) at the six-month mark.
Those who reported COVID-19 symptoms at all follow-up times, or reported worsening symptoms, were more likely to be older and to have pre-existing health problems.
These findings, ultimately, are observational in nature. Moreover, researchers acknowledge several limitations, including that they focused on only wild type SARS-CoV-2 among an unvaccinated population and relied entirely on self-reported health ratings. However, this project did feature a large population-based study with regular assessments of a range of health outcomes, and the findings remained quite similar after further analyses, strengthening the credibility of the estimates.
“Persisting health issues create significant challenges for affected individuals and pose an important burden on population health and healthcare services,” study authors write in a media release, calling for clinical trials “to establish effective interventions to reduce the burden of post-COVID-19 condition.”
A better understanding of the trajectory of symptom burden and recovery from long COVID is key when it comes to policy making, treatment decisions, and care coordination, explains a researcher at the University of Southern California in a linked editorial.
The design of future treatments, clinical trials, and policy interventions “will depend on robust studies based on high quality population level data.”
“Additionally, in view of the complexity of symptom trajectories and the unique disease burden experienced by each individual patient with long COVID, patients should be more closely involved in the design and conduct of these studies going forward.”
The study is published in The BMJ.
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