Long-Term Symptoms after COVID-19. Rapid review.
This rapid review is the 1st update in the series “COVID-19: Long-Term Effects of COVID-19” replacing our previous report published on March 3rd, 2021.
For most COVID-19 is a mild and transient disease, although some may experience a prolonged period with symptoms before resolution. Long-term and nonspecific symptoms have been previously reported in connection with other viral infections, and it is thus not surprising that some patients experience long-term symptoms after covid-19. It is already known that people who are admitted to the intensive care unit due to severe lung failure can report long-term functional impairments such as impaired cognitive function and reduced lung function after discharge.
Prolonged symptoms have previously been observed after other viral infections, but since covid-19 has caused a pandemic, it is useful to gather knowledge about which long-term symptoms occur, how long the symptoms persist, and which patient groups have greatest risk of experiencing prolonged symptoms.
In this rapid review, we summarize research on which long-term symptoms occur after COVID-19, how long the symptoms persist and which patient groups that have the greatest risk of experiencing long-term symptoms.
This rapid review is the 1st update in the series “COVID-19: Long-Term Effects of COVID-19” replacing our previous report published on March 3rd, 2021. In this review, only peer-reviewed studies with around six months follow-up or longer, and more than 100 laboratory test positive COVID-19 cases were included. We excluded studies mainly reporting on laboratory or radiological findings.
The findings are based on systematic searches in MEDLINE and WHO Global research on coronavirus disease (COVID-19) database on June 17th, 2021. One researcher screened the search results. Two researchers selected studies for inclusion and summarised study findings. Experts in the field assisted with study inclusion and provided input during the review process.
We assessed included studies in terms of quality and risk of bias using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies and Case Series Studies. Meta-analysis was not feasible, and the results of this rapid review are therefore presented in tables, graphics and narratively.
Characteristics of included studies
We included 20 peer-reviewed studies following patients for six months or longer, analysing symptoms, quality of life or demographic and medical risk factors. Fourteen studies were conducted in Europe, thereof four in Norway. Number of participants ranged from 113 to 8 983 (19 035 in total). Participants in most studies were middle-aged, and one study only enrolled children. Sex distribution was mainly balanced. All studies used laboratory testing to diagnose COVID-19, mainly PCR. All but two studies started enrolling patients before April 2020. Follow ups were performed either at clinics or through online/phone/postal surveys, except for one study which used registry-data. Loss to follow up was generally high and ranged from six to 61%. Eleven studies followed patients who had been hospitalised with COVID-19 (>50% of participants hospitalised in intensive care unit (ICU) or other hospital department). Ten studies included both ICU and non-ICU patients, and one study included a mixed population of hospitalised and non-hospitalised patients. Nine studies followed patients with COVID-19 who did not need hospitalisation (>50% of participants non-hospitalised), including three studies with a mixed-populations with mostly non-hospitalised patients. Our quality assessment indicated that most studies were of fair quality.
Overview of symptoms around six months follow-up
The presence of any symptom six months after COVID-19 hospitalisation ranged from twelve to 81%, with dyspnoea, fatigue, anxiety and sleeping problems most reported across the studies. Five studies reported negative changes in Health-related quality of Life (HRQoL).
The presence of any one symptom at around six months after COVID-19 (non-hospitalised) ranged from eight to 61%, with fatigue, dyspnoea, loss of smell and taste being the most reported. Three studies reported negative impacts on cognitive abilities and activities of daily living.
Overview of grouped signs and symptoms
Participants reported a wide range of symptoms at and beyond six months after COVID-19. Categorisation based on ICD symptom groups revealed that General, Neurological and Pulmonary symptoms were the most common. Whereas hospitalised patients reported a physiologically broad spectrum of symptoms beyond the three most common groups, this pattern was less apparent among non-hospitalised patients. Across symptom groups, hospitalised patients reported more symptoms more frequently than non-hospitalised patients.
Impact on quality of Life
Across eight studies assessing quality of life after COVID-19, a reduction in overall health and quality of life was observed in 25%- 61% of hospitalised patients and 25%-46% of non-hospitalised patients. In critically ill patients, pain was the most detrimental symptom to quality of life after COVID-19. Overall, a reduction in mobility, a higher incidence of anxiety and depression, and fatigue impacted their quality of life most.
Predicting factors for long-term symptoms
Across the ten studies analysing predicting factors for length of symptoms, female sex was the most consistent variable associated with duration of symptoms, independent of hospitalisation status. In addition, severity of COVID-19, multiple symptoms at diagnosis and prior comorbidities were also correlated with length of symptoms.
Most studies only included SARS-CoV-2 test-positive participants and no control group, a strong limitation in evaluating COVID-19 specific long-term effects. Therefore, it remains uncertain how far prevailing symptoms and impact on quality of life are specific to COVID-19 or more generally attributable to a period of illness. Equally, pandemic related infringements on personal liberty, lockdowns and changes to pre-pandemic lifestyle might also be factors underlying reporting of some symptoms. Our findings reflect participants with COVID-19 in studies that were conducted early in the pandemic, and we don’t know how therapeutic advancements, new virus variants or vaccination have and will impact outcomes in the future. The heterogeneity across studies impairs direct comparison of risk estimates, and hence meta-analysis was not feasible. It should be noted that causal relationships cannot be confirmed or refuted based on the included study designs. Larger controlled studies, with participants from throughout the pandemic are needed for a more exhaustive understanding.
Many COVID-19 patients reported prevailing symptoms after infection, with a large proportion continuing to experience one or more symptoms at six months or longer. Severe COVID-19, requiring hospitalisation or intensive care treatment correlated with longer and more severe functional limitations at follow up. Hospitalised patients had a wider range of symptoms than non-hospitalised with general, neurological and pulmonary symptoms being most common among both groups. Women had a higher risk for developing long-term symptoms.