Hospitalised shift workers up to 3 times more likely to be Covid-19 positive

Scientists have found an association between shift work and COVID-19 positivity in hospitalised patients.

Using data from UK Biobank - the world’s largest biomedical database - shift work increased the likelihood of testing positive for COVID-19 in hospitalised patients 2-3 fold, depending on the nature of shift work. The effect persisted even after controlling for known COVID-19 risk factors.

The study involved researchers at The University of Manchester, Radcliffe Department of Medicine at The University of Oxford and the University of West Indies.

Supported by the NIHR Manchester Biomedical Research Centre, Medical Research Council and Wellcome Trust, it is published in the journal Thorax.

Though there are several known risk factors for COVID-19, they do not always explain why COVID-19 outbreaks happen in factories or healthcare settings which is why the investigators investigated the role of shift work.

Shift work was defined in this study as working outside the hours of 9am to 5pm and it is estimated that around a quarter of the UK workforce do some kind of shift work.

The type of shift work or type of occupation, such as health workers, factory workers, didn’t seem to affect the association as occupational exposure to COVID-19 was controlled for in two different ways.

Over half a million people were enrolled in the UK Biobank. Of these 6,442 were tested for COVID-19 in hospital resulting in 498 positive tests between March and August 2020.

In those that had positive tests, 316 did not work shifts, 98 worked irregular shifts and 84 worked permanent shifts, totalling 182. The shift workers were 2.5 to 3 times more likely to be positive with COVID-19 than non-shift workers in those that were hospitalised.

The team also conducted analysis on a subset of biobank participants where the occupational shift work status was updated in 2017.

In the subset, 43,878 participants were used to analyse the effect of shift work with 72 participants being hospitalised for COVID-19. From this analysis shift workers were an even greater 4.5 times more likely to be positive for Covid-19.

The study was led by Dr John Blaikley, a MRC clinician scientist at The University of Manchester and Dr Hannah Durrington also at The University of Manchester. Both authors are Respiratory doctors at Wythenshawe Hospital.

Dr Blaikley said: “This study shows quite a strong association between shift working and being hospitalised for Covid-19, even after controlling for existing COVID-19 risk factors.”

Dr Durrington said: “It is of paramount importance that the health and working conditions for shift workers are improved.”

Dr Blaikley added: “The UK Biobank does not fully reflect the diversity of the UK, therefore further studies especially in ethnic minority populations are needed.

“It’s hard to explain the exact cause of this association though we think workplaces should be made aware of these risks so they can take appropriate precautions for their staff.

“And we do believe it should be possible to substantially mitigate these risks through good handwashing, use of face protection, appropriate spacing and vaccination”, concluded Dr Durrington.

The paper ‘Shift work is associated with positive COVID-19 status in hospitalised patients’ is published in Thorax and an embargoed copy is available  here