Fit notes associated with COVID-19 in 24 million patients’ primary care records: A cohort study in OpenSAFELY-TPP

Background Fit notes (“sick notes”) are issued by general practitioners (GPs) when a person can’t work for health reasons and is an indication of the public health and economic burden for people recovering from COVID-19. Methods With NHS England approval, we used routine clinical data from >24 million patients to compare fit note incidence in people 18-64 years with and without evidence of COVID-19 in 2020, 2021 and 2022. We fit Cox regression models to estimate adjusted hazard ratios, overall and by time post-diagnosis and within demographic subgroups. Results We identified 365,421, 1,206,555 and 1,321,313 people with evidence of COVID-19 in 2020, 2021 and 2022. The fit note rate was 4.88 per 100 person-months (95%CI 4.83-4.93) in 2020, 2.66 (95%CI 2.64-2.67) in 2021, and 1.73 (95%CI 1.72-1.73) in 2022. Compared with the age, sex and region matched general population, the hazard ratio (HR) adjusted for demographics and clinical characteristics over the follow-up period was 4.07 (95%CI 4.02-4.12) in 2020 decreasing to 1.57 (95%CI 1.56-1.58) in 2022. The HR was highest in the first 30 days post-diagnosis in all years. Conclusions Despite likely underestimation of the fit note rate, we identified a considerable increase among people with COVID-19, even in an era when most people are vaccinated. Most fit notes are associated with the acute phase of the disease, but the increased risk several months post-diagnosis provides further evidence of the long-term impact. Evidence before this study We searched Pubmed from 1 March 2020 to 30 June 2023 using the following search terms: (“COVID-19” OR “SARS-CoV-2” OR “coronavirus”) AND (“United Kingdom” OR “England” OR “Britain” OR “Scotland” OR “Wales”) AND (“fit note” OR “sick note” OR “sick leave” OR “sickness absence”). We also searched the reference list of relevant articles. We included both peer-reviewed research studies and grey literature that quantified receipt of fit notes or sick leave during the COVID-19 pandemic. We found two peer-reviewed studies and one briefing by an independent think tank. A study of 959,356 National Health Service (NHS) employees in England quantified receipt of non-COVID-19 related fit notes during the first wave of the pandemic. They found that the overall fit note rate was lower in 2020 compared with 2019. However, increases in the number of people receiving fit notes were observed for respiratory, infectious disease, and mental health conditions. The second study of 15,931 domiciliary care workers in Wales between Mar 2020 and Nov 2021 found that 15% had been issued a fit note over the study period. Fit notes were more common among women, people ≥45 years, and those with comorbidities. The briefing found that the percentage of sickness absence days taken by NHS employees was higher in 2022 (5.6%) compared with 2019 (4.3%), with a particular increase in absences due to mental health and infectious diseases. In 2022, 18% of sickness absence days were attributable to COVID-19. Added value of this study This study is the first to quantify changes in fit note rate since the start of the COVID-19 pandemic among people with a reported SARS-CoV-2 infection and how this compares with the general population in the UK. We found that people with evidence of SARS-CoV-2 infection had a higher fit note rate than the general population, even after adjusting for demographics and clinical characteristics. While this increased risk was greatest in 2020 (hazard ratio [HR] = 4.07, 95%CI 4.02-4.12), it continued to a lesser extent even into 2022 (HR = 1.57, 95%CI 1.56-1.58). The fit note rate was greatest in the first 30 days post-diagnosis, suggesting that most sick leave is associated with the acute phase. In subgroup analyses, the groups with the greatest relative increased risk changed over the years. People aged 18-24 years had a larger relative increased risk of fit notes (as measured by HR) in 2022 than 2021, when compared with the general population in each year. Additionally, while in 2020 and 2021 the HR increased along with lessening deprivation, this effect dissipated in 2022. In contrast, people hospitalised with COVID-19 were less likely to be issued a fit note than the pneumonia cohort, suggesting the long-term effects may be similar to comparable severe respiratory infections cases resulting in hospitalisation. Implications of all the available evidence While we have likely underestimated the fit note rate due to overcounting of people in the workforce and misclassification of COVID-19 status, we still identified a substantial increased risk of receiving a fit note in people with COVID-19 compared with the general population over all years, even after adjusting for demographics and a wide range of clinical characteristics. The increased risk persisted into 2022, in an era where most people are vaccinated and the severity of COVID-19 illness is lessened. Given the high infection rates still occurring, these findings provide evidence for a substantial impact of COVID-19 on productivity and further evidence of the long-term impacts of COVID-19. ### Competing Interest Statement Over the past five years BG has received research funding from the Laura and John Arnold Foundation, the NHS National Institute for Health Research (NIHR), the NIHR School of Primary Care Research, the NIHR Oxford Biomedical Research Centre, the Mohn-Westlake Foundation, NIHR Applied Research Collaboration Oxford and Thames Valley, the Wellcome Trust, the Good Thinking Foundation, Health Data Research UK (HDRUK), the Health Foundation, and the World Health Organisation; he also receives personal income from speaking and writing for lay audiences on the misuse of science. ### Funding Statement The OpenSAFELY Platform is supported by grants from the Wellcome Trust (222097/Z/20/Z) and MRC (MR/V015757/1, MC\_PC-20059, MR/W016729/1). In addition, development of OpenSAFELY has been funded by the Longitudinal Health and Wellbeing strand of the National Core Studies programme (MC\_PC\_20030: MC\_PC\_20059), The NIHR funded CONVALESCENCE programme (COV-LT-0009), NIHR (NIHR135559, COV-LT2-0073), and the Data and Connectivity National Core Study funded by UK Research and Innovation (MC\_PC_20058), and Health Data Research UK (HDRUK2021.000, 2021.0157). The views expressed are those of the authors and not necessarily those of the NIHR, NHS England, Public Health England or the Department of Health and Social Care. Funders had no role in the study design, collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the Health Research Authority (Research Ethics Committee reference 20/LO/0651) and by the London School of Hygiene and Tropical Medicine Ethics Board (reference 21863). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data were linked, stored and analysed securely using the OpenSAFELY platform, , as part of the NHS England OpenSAFELY COVID-19 service. Data include pseudonymised data such as coded diagnoses, medications and physiological parameters. No free text data are included. All code is shared openly for review and re-use under MIT open license (). Detailed pseudonymised patient data are potentially re-identifiable and therefore not shared.