New research revealed that night work and sleep debt are associated with higher rates of infections among nurses. Sleep debt showed a strong dose-dependent relationship with multiple infection types.

Researchers from the Norwegian Competence Center for Sleep Disorders and the University of Bergen analyzed data from 1,335 active Norwegian nurses to investigate associations among shift work characteristics, sleep patterns, and self-reported infections. They used data collected in 2018 from wave 10 of a larger ongoing longitudinal cohort study called "SUrvey of Shift work, Sleep, and Health (SUSSH)" for this cross-sectional analysis.

Data on sleep duration, sleep need, shift work characteristics, and frequency of infections experienced in the previous 3 months were reported by participants and collected. Chi-square tests and logistic regression analyses, adjusted for sex, age, children at home, and marital status, were used.

Among the nurses studied, 90.4% were female with a mean age of 41.9 years. The most commonly reported infection was the common cold (66.9%), followed by gastrointestinal infections (22.1%), sinusitis (12.2%), urinary tract infections (6.4%), and pneumonia/bronchitis (6%). Overall, 73.5% of nurses reported experiencing at least one infection during the 3-month period.

From this data, sleep debt—the difference between how much sleep a person needs vs. how much they actually get—emerged as a particularly strong predictor of infection risk. Nurses with more than 2 hours of sleep debt had significantly higher odds of reporting common colds (adjusted odds ratio [aOR] = 2.32, 95% confidence interval [CI] = 1.30-4.13), pneumonia/bronchitis (aOR = 3.88, 95% CI = 1.44-10.47), sinusitis (aOR = 2.58, 95% CI = 1.19-5.59), and gastrointestinal infections (aOR = 2.45, 95% CI = 1.39-4.31) compared with nurses who had no sleep debt, the researchers reported in their Chronobiology International article. 

Night work was specifically associated with an increased risk of common cold (aOR = 1.28, 95% CI = 1.00-1.64), and 70.4% of night workers reported common colds compared with 63.9% of day workers. The number of night shifts worked also showed a correlation: Nurses who worked one to 20 night shifts in the past year had a higher likelihood of reporting common colds (aOR = 1.49, 95% CI = 1.08-2.06) compared with those who worked no night shifts.

The researchers found no significant association between absolute sleep duration and infections, nor between quick returns (rest intervals of less than 11 hours between consecutive shifts) and infections.

They suggested that sufficient sleep may prevent infections, but also acknowledged that longitudinal and experimental studies would be needed for causal inferences. To help reduce sleep debt and potentially lower infection risk, the researchers recommended that nurses maintain consistent sleep schedules and suggested workplace strategies, such as optimizing forward-rotating shifts, limiting consecutive night shifts, allowing days off after the last night shift, and promoting the benefits of adequate sleep.