Biphasic sleep in shift workers and its related outcomes: a scoping review protocol.

introductionShift 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. METHODS AND ANALYSIS: 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. ETHICS AND DISSEMINATION: 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. TRIAL REGISTRATION NUMBER: This project is registered with the Open Science Framework accessible at 10.17605/OSF.IO/WY7KJ.