Shift work is associated with disrupted sleep, circadian misalignment and increased risks of adverse health, performance and safety outcomes. Although recommendations for shift workers typically focus on obtaining one long sleep period, many shift workers divide sleep into two episodes, referred to as biphasic sleep. Biphasic sleep may help mitigate sleep loss-related impairments, yet its prevalence, characteristics and potential benefits for shift working populations remain unclear. Existing reviews have examined sleep duration, mental health, or the consequences of shift work broadly, but none have specifically mapped evidence comparing biphasic and monophasic sleep between shifts. This scoping review will identify and summarise the available literature on biphasic sleep among adult shift workers. In addition, we will describe the outcomes and subsequently highlight any possible gaps to inform future research.

This review will follow the Joanna Briggs Institute methodology for scoping reviews and be reported in accordance with the preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews guidelines. Biphasic sleep is defined as two distinct sleep episodes within a 24-hour period between work shifts, including two similarly timed sleep periods or one longer sleep combined with a shorter nap. A comprehensive search will be conducted in April 2026 in MEDLINE, Embase, PsycINFO, Web of Science and CENTRAL using controlled vocabulary (eg, Medical Subject Headings) and free-text terms related to shift work and split sleep. Peer-reviewed primary research examining biphasic sleep among adult shift workers will be included, and studies focusing solely on naps during work hours will be excluded. Two reviewers will independently screen titles/abstracts and full texts, with discrepancies resolved through discussion or by consulting a third reviewer. Data will be extracted using a standardised template including study characteristics, sleep parameters and reported outcomes. Results will be summarised descriptively and presented in tables and evidence maps. No statistical synthesis will be performed.

This scoping review will synthesise data from articles published in peer-reviewed journals. As no primary data will be collected and no human participants will be involved, the review is exempted from formal ethical approval. Findings will be disseminated in terms of a peer-reviewed publication and will inform future systematic reviews on sleep strategies among shift workers.

This project is registered with the Open Science Framework accessible at 10.17605/OSF.IO/WY7KJ.

To systematically review the evidence on the association between non-standard working time arrangements (such as night work or shift work) and the occurrence of safety incidents.

Systematic review conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and using a structured narrative approach and the Synthesis Without Meta-analysis framework to evaluate and summarise findings.

MEDLINE, Embase, PsycINFO, Web of Science and ProQuest Health and Safety Science Abstracts were searched through February 2024.

We included peer-reviewed English-language studies of paid workers (18–70 years) that examined the association between non-standard working time arrangements and safety incidents (accidents, near-accidents, safety incidents or injuries), excluding cross-sectional designs and studies on unpaid workers, athletes or military personnel.

Two reviewers independently extracted data and assessed risk of bias using standardised forms, extracting study characteristics (author, year, country, sector and population), working time arrangements and exposure assessment, outcomes and their assessment, and reported risk estimates. We conducted a narrative synthesis, classifying studies into three exposure contrasts (shift worker versus non-shift worker, time-of-day and shift intensity), and summarised risk estimates using forest plots without calculating pooled effects.

A total of 13 569 records were screened, and 24 studies met the inclusion criteria. The results indicated that shift workers generally had an elevated safety incident risk compared with non-shift workers (risk estimates ranged from 1.11 to 5.33). Most of the included studies found an increased risk of safety incidents during or after night shifts. Accumulated exposure to evening or night shifts increased the risk of safety incidents during the following 7 days. However, bias and heterogeneity across studies in design, populations and outcome measures resulted in an overall low to very low certainty of the evidence.

Non-standard working time arrangements, including night and evening shifts, appear to increase the risk of occupational safety incidents. Despite the low certainty of evidence, the findings highlight a potential area for preventive measures in work scheduling. Future longitudinal studies using individual data on daily working hours are needed.