Fit notes associated with COVID-19 in 24 million patients’ primary care records: A cohort study in OpenSAFELY-TPP
Authors: Schaffer Andrea L , Park Robin Y , Tazare John , Bhaskaran Krishnan , MacKenna Brian , Denaxas Spiros , Dillingham Iain , Bacon Sebastian CJ , Mehrkar Amir , Bates Chris , Goldacre Ben , Greaves Felix , Macleod John ,   The OpenSAFELY Collaborative,   National Core Studies Collaborative, Tomlinson Laurie A , Walker Alex J 
Published: August 2023

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.