Night shift work tied to higher long COVID risk

What happened

A new study led by ISGlobal, with the Germans Trias i Pujol Research Institute (IGTP), reports early evidence that night shift work and chronic insomnia may raise the risk of developing long COVID.

The findings were published in the Scandinavian Journal of Work, Environment and Health and draw on data from the GCAT | Genomes for Life-linked COVICAT cohort in Catalonia.

• Researchers focused on circadian disruption (night work) and sleep disruption (chronic insomnia).
• They examined long COVID as persistent symptoms lasting more than three months after infection.

What the evidence shows about night shift work and long COVID risk

This was an observational, population-based cohort study that followed 2,941 adults in Catalonia between 2021 and 2023.

Among 1,899 participants who became infected with SARS-CoV-2, 284 developed long COVID during the two-year follow-up.

• Compared with day workers, night shift workers had an 88% higher risk of developing long COVID after accounting for other risk factors such as vaccination history or chronic diseases.
• The association was stronger in night workers with obesity.
• Higher risk appeared in both current and former night workers, which the authors say suggests longer-term effects of circadian disruption rather than only short-term schedule changes.
• Night shift work was not linked to a higher risk of becoming infected, which the authors interpret as pointing to differences in recovery rather than differences in catching the virus.

Chronic insomnia and long COVID risk: a separate and combined signal

Chronic insomnia was also linked to a higher risk of long COVID in this cohort, independent of night shift work.

When night shift work and chronic insomnia occurred together, risk rose more than either factor alone.

• Chronic insomnia was associated with a 42% higher risk of long COVID.
• Night shift workers with chronic insomnia were 2.7 times more likely to develop long COVID than day workers without insomnia.
• The study authors describe this pattern as a synergistic effect of circadian disruption plus insomnia.

Why night shift work and long COVID risk matters for metabolic health

Circadian and sleep disruption can intersect with metabolic health because obesity appeared to strengthen the night work–long COVID association in this study.

For readers focused on recovery, the findings point to sleep and circadian alignment as potentially modifiable factors that may influence the transition from acute infection to persistent symptoms.

• The authors note that studies in humans show internal clock disruption can weaken immune responses and increase susceptibility to infections.
• They also cite prior pandemic-era evidence from the U.K. linking sleep disturbances to higher SARS-CoV-2 infection risk, and position this new work as extending the question to long COVID.
• Proposed mechanisms in the paper include timing of pathogen exposure affecting immune response and circadian disruption impairing the immune system’s ability to clear infection (mechanisms not yet fully understood).
• A practical discussion to have with a clinician or occupational health team is whether work schedules and sleep habits can be adjusted to reduce circadian disruption, especially for night shift workers.

Limitations and what to watch next

Because this was a cohort study, it can show an association but cannot prove that night shift work or insomnia causes long COVID.

The researchers also flag important boundaries on who the results may apply to and what other factors could still be at play.

• Participants were ages 40 to 65, so findings may not apply to younger or older groups.
• Other occupational factors, such as work-related stress, cannot be completely ruled out.
• Strengths include a well-characterized population-based cohort, detailed data on work schedules and sleep habits, and use of an internationally recognized definition of long COVID.