Mini-symposium: Chronic diseases in shift work: recent mechanistic insights and prevention strategies
Wednesday 8 October 2025, 11.00 – 12.30 Glow
Moderated by Heidi Lammers-van der Holst
Shift work and chronic disease prevention: Where do we stand?
Heidi Lammers-van der Holst
Uncovering the biological and behavioral mechanisms underlying the pathogenicity of night work
Kyriaki Papantoniou (presenter)
Isabel Santonja, Sandra Haider, Vanessa Schoissinger, Katrin Scionti, Heidi Lammers, Monique Vingerhoeds and Karl-Heinz Wagner, on behalf of the ShiftHealth consortium
Abstract
Objective: The International Agency for Research on Cancer (IARC) recently classified night work as a probable human carcinogen and highlighted the lack of mechanistic studies in real-world settings. This study investigates behavioral and biological pathways linking night work to cancer and obesity risk, and explores the role of sleep and circadian disruption.
Methods: As part of the SHIFT2HEALTH project, a mechanistic study is being conducted recruiting 200 night shift and 200 day workers from multiple occupational sectors in Austria and the Netherlands. All participants complete questionnaires on work schedules, lifestyle, diet, and sleep. Participants provide fasting blood samples (for inflammatory, oxidative stress, and appetite hormone markers), first-morning urine (for melatonin), stool samples (for gut microbiome), hair samples (for chronotype). Night shift workers additionally collect 24-hour urine samples across a night and a day shift (for 6-sulfatoxymelatonin rhythm), dried blood spots pre- and post-shifts (for metabolomics), repeated tongue swabs (for oral microbiome) and wear and actiwatch for 7–10 days capturing sleep, activity, and light exposure continuously. We will use linear regression models with biomarker levels as the outcomes and night work as the exposure adjusting for potential confounders. Expected
Results: We will present prior mechanistic evidence, the study protocol and preliminary results from the SHIFT2HEALTH project on a variety of biomarker levels including hormones and inflammatory markers linked to night work. We will also explore the role of sleep and circadian misalignment based on actigraphy data, and assess susceptibility to night shift work according to sleep characteristics and chronotype.
Conclusion: The SHIFT2HEALTH study is among the most comprehensive real-world mechanistic studies of night shift work to date. The results will help identify key biological pathways underlying increased carcinogenic and metabolic risks, supporting future risk stratification and targeted occupational health interventions. Funding: Research related to this abstract was funded by the EU HEALTH call “HORIZON-HLTH-2022-STAYHLTH-01-05 (Grant agreement ID: 101080788)
How does night work-induced circadian disruption influence low-grade inflammation?
Kirsten Nabe-Nielsen (presenter)
Kyriaki Papantoniou , Anne Emily Saunte Fiehn Arup , Mette Sallerup , Helena Breth Nielsen , Anne Helene Garde
Abstract
Objective Night work disrupts circadian rhythms by misaligning the sleep–wake cycle with the solar day and has been classified as probably carcinogenic to humans by the International Agency for Research on Cancer (IARC). Increased inflammation is a proposed mechanism linking night work–induced circadian disruption to cancer; however, most supporting evidence comes from experimental rodent studies. This study aims to investigate the effect of night work–related circadian disruption on low-grade inflammation, measured by C-reactive protein (CRP) levels, in a female human population. Specifically, we examine acute and chronic effects, reversibility, and cumulative exposure to night work on CRP.
Material and methods We used baseline data from the 1001 nights-cohort, which includes 1,075 women employed in Danish hospitals. Participants were eligible for inclusion in the analyses if they provided a blood sample for CRP measurement of CRP-concentration and had complete data on key variables, including age, anthropometric measures, self-reported health, and recent infections (n = 960). Night work exposure was assessed via self-reported current work schedule, night work intensity, number of consecutive night shifts, time since the last night shift, and number of night shifts in the previous week. We used linear regression to analyze associations between night work and log-transformed CRP concentrations.
Results In preliminary age-adjusted models, CRP concentrations were 57% higher in permanent night workers compared with permanent day workers (95% CI: 11%–121%), and 38% higher compared with rotating night shift workers (95% CI: 1%–63%).
Conclusion This study adds to the limited evidence on the relationship between night work–induced circadian disruption and low-grade inflammation in humans. By improving our understanding of how night work influences inflammatory markers, these findings may offer insights into its broader health implications, including cancer risk. Funding The present study was funded by the Danish Working Environment Research Fund.
Evaluating quick return restrictions on sickness absence in healthcare employees: A difference-in-differences study
Jarno Turunen (presenter)
Kati Karhula ; Annina Ropponen ,; Rahman Shiri ; Kari Hämäläinen ; Jenni Ervasti ; Aki Koskinen ; Olli Haavisto ; Mikael Sallinen ; Jaakko Pehkonen ; Mikko Härmä
Abstract
Background: Quick returns in shift work have been linked to adverse health effects. The 2020 reform of Working Time Act in Finland limited rest periods under 11h in irregular shift work.
Design and methods: This observational longitudinal study, analysed as a quasi-experiment, used a difference-in-differences regression analysis with unit and time fixed effects and robust standard errors to evaluate the changes in quick returns and sickness absence following the 2020 reform. We assessed changes in sickness absence from 2019 to 2021 across hospital work units. The study compared units mandated to limit quick returns (Treatment group; 416 units, over 20,500 employees, 72% in nursing) with units that had low levels of quick returns prior to the reform and did not need to limit quick returns (Control group; 37 units, over 1700 employees, 70% in nursing).
Results: Simple regression analysis with fixed effects for unit and time over 2019–2020 showed a less pronounced increase in sickness absence by −0.7 percentage points (95% confidence interval [CI]: −1.3 to −0.1) for the treatment group compared to the control group, indicating a 13 % lower rate of sickness absence. For the period 2019–2021, the estimate was −0.5 percentage points (95% CI: −1.0 to 0.0). When incorporating covariates and inverse probability weighting, the estimates were more substantial with narrower confidence intervals: −0.9 percentage points (95% CI: −1.4 to −0.3) for 2019–2020, and −0.6 percentage points (95% CI: −1.2 to −0.1) for 2019–2021.
Conclusion: The problematic characteristics and consequences of shift work can be controlled, through legislation also. Policymakers and managers should evaluate and adjust the frequency of quick returns to achieve the potential effects on employee well-being, health, and operational efficiency, which in this study was indicated by the reduction in sickness absence.
PerfectFit@Night: An intervention to enhance sleep, fatigue, and recovery for healthcare shift workers
Karen Oude Hengel (presenter)
Heidi M Lammers-van der Holst, Fleur van Elk, Suzan JW Robroek, Alex Burdorf
Abstract
Objectives: Previous intervention studies among night workers mainly focused on single interventions and found inconclusive evidence for effectiveness. The current study aims to evaluate the effects and implementation of the PerfectFit@Night intervention to improve sleep, fatigue and recovery of night workers in healthcare.
Methods: PerfectFit@Night consisted of environmental (provision of a powernap bed and healthy food, and workshop healthy rostering) and individual elements (e-learning and sleep coaching) and was implemented for three months in a phased manner to night workers in the health care (n=210). Questionnaires, logbooks and interview data were used. Effects of the intervention on sleep, fatigue and recovery were evaluated and implementation factors were evaluated.
Results: Night shift-related insomnia (-11 %-points, 95 % CI: -19 %, -4 % at three months), need for recovery (β: -2.45, 95 % CI: -4.86, -0.03 at six months) and fatigue (OR: 0.46, 95 % CI: 0.25, 0.86 at six months) decreased significantly after the intervention. No changes were found for subjective sleep quality and sleep duration. Barriers and facilitators for implementation were identified for each intervention element at individual (e.g., dietary preferences), organisational (e.g., responsibilities at work) and workplace levels (e.g., location of power nap bed), and for the intervention itself (e.g., useful information in e-learning). Although satisfaction was high and continuation was preferred, embedding of the intervention in the daily routine was limited.
Conclusions: The PerfectFit@Night intervention reduced insomnia, fatigue and need for recovery in night workers in healthcare. The most important facilitators to improve the implementation of PerfectFit@Night exist at the organisational level (e.g., positive attitude within the culture and suitable work demands). Combining effect and implementation evaluation is crucial to identify barriers and facilitators that hamper or enhance intervention effects.
The impact of a sleep intervention on shift workers: Improved subjective sleep without objective changes
Maaike van der Rhee (presenter)
Johanneke E. Oosterman, Suzan Wopereis, Martijn E.T. Dollé, Alex Burdorf, Linda W.M. van Kerkhof , Heidi M. Lammers-Van der Holst
Abstract
Objective Shift work is associated with disturbed sleep and adverse health effects. The aim of this study is to analyze the effects of two interventions, i.e. personalized sleep or nutritional advice, on sleep duration and quality in real-life shift workers.
Methods This controlled intervention study included 57 healthy shift workers working 12-hour shifts. Participants received tailored advice based on their work schedule, social obligations, and physiological markers. The sleep advice focused on sleep timing, multiple sleep episodes, and sleep hygiene education, while the nutritional guidance structured meal timing, macronutrient distribution, and energy intake. Sleep was assessed objectively through actigraphy at baseline, start intervention and post-intervention (averaging 13 night shifts, 6 early shifts and 20 free days per participant). Subjective sleep was measured with the Insomnia Severity Index at baseline, post-intervention and follow-up. Mixed-effects models with a random intercept were used, adjusted for age, chronotype and household.
Results Participants experienced on average shorter sleep duration when working night and early shifts, compared to recovery days. Neither intervention changed the objective sleep duration or quality. Participants who received the sleep advice had significantly higher insomnia scores at baseline, and their scores had decreased to match those of the other groups on post-intervention and during follow-up 8 months after the intervention. No such effects were observed for the nutritional guidance.
Conclusion Personalized sleep guidance improved subjective sleep experience (insomnia scores) but had no effect on objective sleep measures, highlighting the disconnect between subjective experience and objective sleep metrics.