SHIFT workers are up to three times more likely to be hospitalised with Covid, according to a new study.

Researchers used data for more than 280,000 people aged 40 to 69 at the time they were enrolled in the UK Biobank, between 2006 and 2010.

They compared participants who had never worked shifts against those who worked irregular or permanent shifts.

Those doing permanent shift work were 2.5 times more likely to be hospitalised with Covid, even after taking into account of other factors including age, sex, and ethnicity.

Working irregular night shifts was associated with being three times more likely to test positive for the virus in hospitals.

These higher risks were largely unchanged even after accounting for factors such as sleep duration, BMI, alcohol and smoking.

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The researchers defined shift work as a work schedule that falls outside regular work hours of 9am and 5pm, including both long-term night shifts and work schedules in which employees change or rotate their shifts.

The researchers suggest their findings may be due to increased occupancy of workspaces over 24 hours for shift workers, resulting in reduced time for cleaning between shifts and tiredness leading to less awareness of health and safety measures.

Other explanations could be that shift work might alter how the immune system responds to infection.

Previous studies have found that shift work increases the risk of developing respiratory disease, diabetes, and cancer.

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Given that the immune system is regulated by the circadian clock, it is possible that shift work could be causing “circadian misalignment” and increasing a person’s susceptibility to Covid.

Author Dr John Blaikley, of Manchester University, 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.”

Co-author Dr Hannah Durrington added: “We do believe it should be possible to substantially mitigate these risks through good handwashing, use of face protection, appropriate spacing and vaccination.”

The findings are published in the BMJ journal Thorax