A new study examining the effects of sleep patterns and shift work on the immune system has found that sleep debt and night shifts increase the risk of several common infections in nurses.
Modern society relies on shift work, which requires employees to work outside of traditional hours. While essential in sectors such as healthcare, growing evidence suggests that these work patterns may negatively impact worker's health.
This study, which analysed self-reported data from 1,335 Norwegian nurses, found that shift work – particularly night shifts – was associated with a higher risk of several infections, including the common cold.
Published today in Chronobiology International , the peer-reviewed findings emphasise the importance of adequate sleep and shift management in reducing susceptibility to infection.
"These findings highlight the need for tailored interventions to reduce infection risks among healthcare workers," says Siri Waage, senior author of the study, who is the coordinator at the Norwegian Competence Center for Sleep Disorders, Haukeland University Hospital, Bergen.
"Sleep debt and irregular shift patterns, including night work, not only compromise nurses' immune health but could also impact their ability to provide high-quality patient care."
The researchers analysed data from the Survey of Shift work, Sleep and Health (SUSSH) study, collected in 2018. The participants – mostly female nurses (90.4%), with an average age of 41.9 years – reported their sleep duration, sleep needs, shift work patterns, and how often they had experienced specific infections over the past three months.
Statistical analyses, adjusted for factors such as age, gender, marital status, and childcare responsibilities, revealed a clear link between slept debt, night work and infection risk.
The study found that sleep debt, defined as the gap between sleep need and actual sleep duration, increased infection risk in a dose-dependent manner:
- Nurses with moderate sleep debt (1-120 minutes less sleep than needed) had a 33% higher risk of the common cold, while those with severe sleep debt (more than 2 hours) had more than double compared to those with no sleep debt.
- The risk of pneumonia/bronchitis was 129% higher for moderate sleep debt and 288% for severe sleep debt.
- Both sinusitis and gastrointestinal infections also showed higher risks with increasing levels of sleep debt.
The analysis also revealed that night work was linked with an increased risk of the common cold, but was not associated with any of the other infections examined. In contrast, sleep duration and 'quick returns' (short intervals between consecutive shifts) were not associated with infection risk.
These findings suggest that ensuring sufficient sleep may help prevent infections, although further research is needed to determine cause-and-effect relationships.
The authors propose several strategies that might help reduce sleep debt and potentially lower infection risks among nurses in the future.
"Nurses could benefit from optimised shift patterns, such as limiting consecutive night shifts and allowing adequate recovery time between shifts," adds co-author Professor Ståle Pallesen, whose research specialisms blend psychology and insomnia, at the Department of Psychosocial Science at University of Bergen.
"Raising awareness about the importance of sleep for immune health and encouraging regular health screening and vaccinations for healthcare workers may also be helpful."
A key strength of this study is its large sample size and focus on predominantly female nurses over 30, making it well-suited to analysing associations between sleep patterns and infection risk in this group. However, the findings may not be generalisable to men, younger nurses, other professions, or those with different shift work schedules.
Additionally, since data collection took place in the spring, outside the typical flu season, infection rates may have been lower than if the survey had been conducted in winter.
