Although the existence of long COVID has become more widely recognised, little is known about the epidemiology of the condition in terms of mortality, health service utilisation and organ-specific impairment.
According to guidance from NICE, long COVID does not represent a single condition but rather signs and symptoms that develop following an infection consistent with COVID-19 and which continues for more than 12 weeks. However, to date, most studies have focused on the symptoms of long COVID rather than the impact on different organ systems and such studies have not included a control group to provide some assessment of counterfactual (or unobserved) outcomes. As a result, a team of UK government statisticians sought to retrospectively analyse outcomes for patients discharged from hospitals after an acute infection with COVID-19.
The team used national electronic health records and death registrations for individuals in England. People were included in the analysis if they had a hospital episode between January and August 2020 and a primary diagnosis of COVID-19 based on either clinical symptoms or a positive PCR test result. In order to compare these outcomes, the researchers matched COVID-19 patients both demographically and clinically with a group of control patients who did not meet the COVID-19 inclusion criteria. All COVID-19 patients were followed-up from their index data (i.e., when they went to hospital) until the end of September 2020. The outcomes of interest were all-cause mortality, hospital readmission for any reason, respiratory disease, major adverse cardiovascular events (MACE), diabetes, chronic kidney disease (CKD) and chronic liver disease (CLD) and these diagnoses were captured from either hospital or primary care records.
From a total of 86,955 individuals hospitalised with COVID-19, 53,795 had been discharged alive at the end of the data collection period. A total of 47,780 were matched with controls and included in the final analysis. COVID-19 patients were followed for a mean of 140 days and 153 days for control patients. The mean age of COVID-19 patients at baseline was 64.5 years of whom 54.9% were male. Overall, COVID-19 patients were more likely to be aged 50 years and over, male, living in deprived areas, former smokers, overweight or obese and with more co-morbidities than matched controls. From the 47,780 COVID-19 patients discharged, 29.4% were re-admitted and 12.3% died with the re-admission and death rates being 3.5 and 7.7 times greater respectively, than those of matched controls. Respiratory disease was diagnosed in 29.6% of those discharged of which nearly half (43%) were defined as new-onset. Post-discharge diagnoses of MACE, CKD and CLD occurred in 4.9%, 4.8% and 1.5% respectively which was again more frequent compared to controls. Summarising their findings, the authors reported that their data indicated that being hospitalised with COVID-19 was associated with an increased risk of readmission and death following discharge compared to individuals with a similar demographic and clinical profile.
They also noted that the results showed that the long-term burden of COVID-related morbidity on both hospitals and the wider healthcare system are likely to be substantial as more people are admitted to hospital with the virus.
Ayoubkhani D et al. Epidemiology of post-COVID syndrome following hospitalisation with coronavirus: a retrospective cohort study. MedRxiv 2021