Shift Schedule With Fewer Short Daily Rest Periods and Sickness Absence Among Health Care Workers: A Cluster Randomized Clinical Trial.

Importance: Some shift work arrangements allow for less than 11 hours off between shifts. The consequences of short daily rest periods are currently not well understood. Objective: To determine the effect and cost-benefit of reducing the number of short daily rest periods on sickness-related absence among health care workers. Design, Setting, and Participants: This 2-arm cluster-randomized clinical trial was conducted between January 11, 2021, and May 22, 2022, in hospital care units at Haukeland University Hospital in Bergen, Norway. Statistical analysis was performed from April to May 2025. Intervention: The intervention group followed a 6-month shift schedule with reduced instances of short daily rest periods, whereas the control group adhered to a 6-month shift schedule maintaining the usual number of short daily rest periods. Main Outcomes and Measures: Primary analyses followed intention-to-treat principles. The outcome was change in sickness-related absence days and absence spells (ie, each uninterrupted period of ≥1 consecutive sickness-related absence days) over the final 5 months of the intervention (allowing a 1-month stabilization period), compared with the same period in the preceding year and against a control group. The economic returns, measured as the increase in net present value of production from reduced sickness-related absence days due to the intervention, was estimated using a standard cost-benefit formula. Results: Of 66 hospital units with 811 health care workers (mean [SD] age, 39.8 [12.8] years; 626 of 808 women [77.5%]) in 80% or more full-time positions, 31 units (344 workers) were randomized to the intervention group and 35 units (467 workers) to the control group. The mean (SD) number of short daily rest periods among the intervention group was halved from 18.0 (8.4) during the reference period to 9.1 (6.2) in the intervention period, while the frequency remained unchanged among the control group (reference period, 18.3 [8.3] days; and intervention period, 17.5 [8.4] days). The intervention group showed a significantly smaller increase in sickness-related absence days (incidence rate ratio [IRR], 0.56; 95% CI, 0.41-0.79; P < .001) and spells (IRR, 0.73; 95% CI, 0.61-0.86; P < .001) compared with the control group. The effect on sickness-related absence days in the intervention units resulted in a positive estimated net economic return of approximately NOK 2 174 620 (USD $213 600) over 5 months. Conclusions and Relevance: In this randomized clinical trial of health care workers, reducing the frequency of short daily rest periods had positive effects on sickness-related absences and reduced expenses. These findings should guide organizational practices and inform legislative policies to enhance the health of workers by increasing daily rest periods to 11 hours or more between shifts. Trial Registration: ClinicalTrials.gov Identifier: NCT04693182.