Dagfinn Matre

Non-standard work shifts (extended hours and night shifts) can impair vigilance and attention, increasing the risk of safety incidents. We present an ongoing study using VR-based eye-tracking to obtain oculometric measures, including saccade kinematics and gaze entropy, across a 16-hour simulated workday. Findings aim to clarify how cognitive states evolve over long shifts and to identify objective biomarkers of fatigue-related safety risk.

Introduction 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. 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.

Objective: This cross-sectional study assesses cardiovascular disease (CVD) risk factors in industrial rotating night shift and day workers. Methods: We examined 27 day workers; 40 night shift workers with high and 34 with low night loads. We assessed sleep, blood pressure (BP), pulse wave velocity (PWV), carotid intima-media thickness (cIMT), maximal oxygen uptake (V̇O2max), glycosylated haemoglobin (HbA1c), lipids, focusing on inflammatory markers, and adipokines. Results: High load night shift workers had higher inflammation and lower adiponectin level compared to other shift workers and day workers. Night shifts of 8 and 12 hours shortened sleep. Number of night shifts was positively associated with inflammatory markers and negatively associated with adiponectin. Conclusions: Night shift work is associated with CVD risk factors. Shift schedules with fewer night shifts and longer recovery periods could mitigate it. Export

Is it a viable strategy to compress the workweek of public health and social care workers into fewer, longer shifts in exchange for fewer workdays? The consequences for both the quality of work and the employee seem to be unclear. Sustaining public health and social care services to protect public welfare requires a stable workforce. Vulnerable patients benefit from continuity of care, trust, and emotionally secure caregiver interactions. A stable workforce also brings advantages to employers, boosting productivity and reducing costs related to sickness absence and employee turnover (1). However, the growing demand for care of the elderly in OECD countries clashes with a shrinking health and care workforce, driven by factors such as early retirements by women, disability, and a shortage of newly trained professionals (2, 3). This scenario creates a self-reinforcing cycle, where fewer staff face rising burdens, leading to retention challenges. In Norway, the municipal health and care sector faces a doctor-certified sickness absence rate of 26% (around one third is reported to be work-related), notably higher than the national average of 7% (4). The majority (60%) of long-term sickness absence is due to musculoskeletal and mental diagnoses (4). The sector is also characterized by a higher proportion of workers leaving the active workforce due to health-related diagnoses than the national average (98 versus 66 per 10 000 workers) (4). Also here, musculoskeletal and mental diagnoses dominate. Prevention strategies targeting sickness absence, early retirement, and disability pension are needed to address the workforce shortage. Turnover intention is affected by family and social responsibilities but is also affected by organizational aspects, such as workload and working time arrangements, which are modifiable (5–7). The health and care sector operates continuously, necessitating shift work, including irregular working hours. In Norway, around 90% of employees in this sector work outside regular daytime hours (4). One type of shift work is the compressed workweek (CWW), where employees work extended daily work hours compensated by a reduced number of workdays, without increasing the total weekly work hours. In a CWW, the worker extends his or her workdays either only during the weekend or throughout the workweek (8). In offshore drilling or industrial work, for example, 12-hour shifts are common. In the USA and the UK, the healthcare sector has adopted 12-hour shifts or even longer ones as part of a 2-shift system (9). In Norwegian municipal health and care services, CWW with extended daily hours has gained attention as a potential solution to workforce stability challenges (10). However, the long-term consequences for employees remain unclear. Moreover, there is a lack of studies investigating how the consequences for employees and service users vary depending on how CWW are organized (11). Important characteristics of compressed schedules – such as shift length, break duration between and during work periods, and the combination of extended and shorter shifts – are largely unexplored. For example, a key distinction must be drawn between CWW with and without compensatory long breaks. If long and short shifts are combined to cover changing staffing needs, this approach may reduce the recovery benefits that compressed schedules are meant to provide (11). Evidence about the consequences of CWW with long shifts remains inconclusive. On the positive side, long shifts paired with extended recovery periods may enhance work–life balance by reducing the commuting frequency and affording workers longer, consolidated periods of personal time (12–14). A Norwegian qualitative study found that long shifts in nursing homes are associated with reduced stress, greater job satisfaction, continuity of care, and lower emotional exhaustion, although it did not assess the long-term consequences thereof (15). Additional time off during the workweek has also been linked to fewer sickness absence days, a relationship likely mediated by the increased opportunities for rest and recovery (16). However, a recent study utilizing workplace-level data did not support the notion that CWW influences sickness absence (17). In the construction sector, compressed schedules appear to alleviate fatigue and time pressure, although these effects were contingent upon individual expectations (18). The downside of long shifts is nevertheless significant, especially in high-stress, caregiving roles. Negative outcomes include increased fatigue and reduced alertness over successive shifts, particularly by the end of a third or fourth long shift (19, 20). Shifts exceeding 12 hours, but not necessarily combined with a compensatory longer break, are associated with elevated risks of safety incidents (21). Importantly, European nurses working ≥12-hour shifts reported lower care quality, more care left undone, and higher rates of burnout compared to those on 8-hour schedules (22), with limited evidence of value propositions being realized (9). A recent systematic review on the consequences of a compressed workweek concluded that findings are mixed, depending on the outcomes, shift length, and alternative schedule (11). Overall, the results indicated increased sickness absence for workers with CWW, while simultaneously reporting higher satisfaction. Significant gaps remain before we understand how CWW affects health and disease. As summarized by Bernstrøm and colleagues (11), the consequences of a CWW are complex and depend on how a CWW is organized, the nature of outcomes it produces, for whom the outcomes are relevant, when the effects occur, as well as how a CWW combines with additional workplace exposures. These challenges align with a recent discussion paper on working hours and health (23) emphasizing the need for register-based exposure assessment, large longitudinal studies, biomarker...

Objectives: Pain is a hallmark of musculoskeletal conditions. Some studies suggest that pain is exacerbated by working in cold environments, potentially due to poorly understood mechanisms within the somatosensory system. The aim of this study was to assess whether ambient cold exposure influences the efficiency of endogenous pain inhibition and the potential role of subjective thermal comfort. Methods: In a crossover study with 1 week interval and in randomized order, 20 healthy men were exposed to cold (COLD; 10 °C) and thermoneutral (TN; 22 °C) conditions in a controlled environment room (CER) for 2 h. Conditioned pain modulation (CPM), defined as the difference in mean rated pain of a test stimuli (TS) with and without a conditioning stimulus (CS), was calculated before and after CER. Test stimuli (TS) was a 30 s tonic noxious heat stimulation to the dominant volar forearm, and conditioning stimuli (CS) was immersion of the contralateral hand in water holding 4 °C. Subjective TS pain was rated on a 0–10 cm computerized Visual Analogue Scale (VAS). Thermal comfort, encompassing subjective thermal perception, evaluation, and preference, was assessed using standardized subjective judgment scales. Results: The CPM-effect was significantly reduced by COLD exposure, but not by TN exposure. As expected, participants’ ratings of thermal comfort changed across exposure conditions; however, this had no significant influence on the CPM-effect. Conclusions: Exposure to cold ambient conditions impaired endogenous pain-inhibitory pathways, an outcome not observed under thermoneutral conditions. Furthermore, the results suggest that thermal comfort does not influence endogenous pain-inhibitory pathways. Further research is required to identify moderators affecting pain processing in cold working environments. Regional Ethics Committee, Norway (REK sør-øst C; application # 2017/1859).

Objectives: We aimed to investigate the prevalence of headaches on days with night shifts compared with days with day shifts within the same individuals, accounting for work‐related psychosocial stressors, physical job demands, and sleep duration and quality. This approach allowed us to isolate the impact of circadian misalignment due to night work from other potential headache triggers.Background: Night work has been suggested to increase the risk of headaches, primarily due to circadian misalignment and disturbed sleep. Most previous studies compare night workers with day workers, but differences in job characteristics and tasks between these groups may introduce bias. To minimize this potential bias, we examined headache occurrence under different working conditions (night vs. day shifts) within the same individuals.Methods: We used data from 14 days of repeated measurements in the 1001 nights‐cohort, which includes female employees from the Danish hospital sector. Data were collected from September 2022 to April 2024. Participants completed diaries for 14 consecutive days, providing daily information on working hours, sleep, work‐related psychosocial stressors, physical job demands, and headache occurrence (yes/no). Participants with data from at least one day shift and at least one night shift were eligible for inclusion in the analyses. In total, 522 participants contributed 3348 measurement days (1926 day shifts and 1422 night shifts). We estimated prevalence ratios (PRs) for headache occurrence while accounting for repeated measures within individuals and with adjustment for possible confounders (adjusted prevalence ratio [aPR]).Results: Headache was reported on 21.5% of measurement days with day shifts and on 27.9% of measurement days with night shifts. Working a night shift was associated with a significantly higher headache prevalence (aPR, 1.31; 95% confidence interval, 1.13–1.52) compared with day shifts when adjusting for work‐related psychosocial stressors, physical job demands, and sleep duration and quality. For consecutive night shifts, the similarly adjusted headache prevalence was highest on the measurement day with the second night shift (aPR, 1.20; 95% confidence interval, 1.02–1.42), using the first night shift as a reference.Conclusion: This study is the first to investigate the headache prevalence when working night shifts compared with day shifts while accounting for work‐related psychosocial stressors and physical job demands. Neither these factors, nor shorter sleep duration or lower sleep quality, explained the increased headache prevalence observed when participants worked night shifts. Thus, other (cascading) effects and underlying mechanisms of night work‐related circadian misalignment may be the primary drivers of headache in night shift workers.

Objective 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. Design 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. Data sources MEDLINE, Embase, PsycINFO, Web of Science and ProQuest Health and Safety Science Abstracts were searched through February 2024. Eligibility criteria for selecting studies 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. Data extraction and synthesis 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. Results 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. Conclusions 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.

Objectives: To assess absolute levels and longitudinal changes in cardiovascular disease (CVD) risk factors over 6 years among rotating shift workers with night shift work and day workers in industry. Methods: We studied three groups, 32 night shift workers in Plant A with a high night load, 23 in Plant B with a low night load and 25 day workers during a 6-year follow-up (FU). We collected demographics by questionnaire, measured blood pressure, resting heart rate, carotid intima–media thickness (cIMT), carotid to femoral pulse wave velocity (cfPWV) and maximal oxygen uptake (V̇O_2max). We analysed blood samples including lipids, glycosylated haemoglobin (HbA1c) and C reactive protein (CRP). Mixed models were used to assess changes and differences in changes of these outcomes between shift and day workers. Results: Over the 6-year FU weight, cfPWV and CRP increased among shift workers with a high night load, and cIMT increased among shift workers with a low night load and among day workers. Over the 6-year FU, a significant decrease in V̇O_2max and an increase in HbA1c were found among all workers. The decrease in V̇O_2max and increase in HbA1c were associated with number of years in shift work. Conclusions: Rotating shift work with night shift work in industry associates with weight increase, inflammation, arterial stiffness, increase in cIMT and HbA1c but also decreased V̇O_2max. Reducing the number of night shifts and including periods of restitution in the shift plan seem to mitigate some of the CVD risk factors.

Objectives Night work disrupts sleep, which may increase inflammatory processes, pain sensitivity and pain perception. We investigated effects of night shifts on musculoskeletal pain (MSP) and other mental and somatic symptoms using day-to-day measurements in a within-person design. We also disentangled the effect of night work from the effects of shift-related differences in job demands and sleep. Methods We included 522 hospital employees with data on ≥1 day shift (n=1926) and ≥1 night shift (n=1422). Participants reported their working hours, MSP, other mental and somatic symptoms, sleep and psychosocial and physical job demands daily for 14 days. We estimated prevalence ratios (PRs) of MSP and symptoms when working night shifts compared with day shifts. Results After adjusting for age and job demands, night shifts were associated with pain in the lower extremities (PR 1.12; 95% CI 1.01 to 1.25), gastrointestinal symptoms (PR 2.12; 95% CI 1.26 to 3.53) and other mental and somatic symptoms (PR 2.54; 95% CI 1.31 to 4.91). Adjustment for sleep duration did not alter these findings. However, longer shift duration may explain the higher occurrence of lower extremity pain during night shifts. Conclusions We found no evidence of a general effect of night work on MSP. Only an acute effect on lower extremity pain was observed, which may be attributable to longer night shift duration. Employees also more frequently reported other types of symptoms when working night shifts, even after adjusting for job demands and sleep duration. Thus, physiological effects related to circadian misalignment may be a plausible explanation.