Barbara Harding , Jesse Thacher , Jelle Vlaanderen , Antonio D’Errico , Anastasiia Snigireva , Frida Wiik , Gunilla Rydenstrand , Roel Vermeulen , Anne Helene Garde , Kirsten Nabe-Nielsen , Karin Broberg , Maria Albin , Manolis Kogevinas

Abstract

Objective Circadian disruption, as experienced by night shift workers, increases the risk of cardiometabolic diseases. The aim of this study is to investigate metabolite alterations and their relation to cardiometabolic outcomes among night shift workers.

Material and Methods Data from exposure measurements, questionnaires including diet, clinical examination (anthropometry including BMI, blood pressure, waist and hip circumference), and biological samples after shift work were collected within the EPHOR-NIGHT project (N=860, day shift n=363, night shift =497) from Sweden, Spain and Denmark. Plasma metabolites (cholesterol, triglycerides, fatty acids, apolipoproteins, HbA1c and fasting blood glucose (the latter two only assessed in the Swedish sub-cohort n=156-169) were quantified by 1 H NMR Spectroscopy and routine clinical assays. Using adjusted linear regression models, including diet, we examined differences in plasma metabolite levels and their association with cardiometabolic risk factors among night shift workers compared with day shift workers.

Results No differences were found for total cholesterol, triglycerides, or apolipoproteins in the whole cohort, nor fasting glucose or HbA1c in the sub-cohort. Night-shift workers had lower fractions of PUFAs, both omega-3 (-0.22, 95% CI -0.38 to -0.07) and omega-6 (-0.56, -0.99 to -0.12), and total PUFAs (-0.78, -1.22 to -0.35). Conversely, they had higher fractions of mono-unsaturated (0.48, 0.11 to 0.84) and saturated fatty acids (0.31, 0.06 to 0.55). Lower fractions of PUFAs and higher fractions of mono- and saturated fatty acids metabolites fractions were in turn significantly associated with higher BMI and higher blood pressure. Further mediation and dose-response analyses will be presented at the conference.

Conclusions We found differences in potential metabolic pathways linking night shift work with cardiometabolic risk. Contributions from other e.g. behavioral and environmental factors cannot be ruled out and warrant further longitudinal investigation. Research funding from the EU Horizon project EPHOR, Swedish Research Council FORTE and AFA insurance.

Tosca O.E. de Crom, Theresa Kynde, Wenxin Wan, Claudia Lissåker, Jenny Selander, Pernilla Wiebert, Henrik Kolstad, Jorunn Kirkeleit, Ingrid Sivesind Mehlum, Karina Undem, Svetlana Solovieva, Ioannis Basinas, Hans Kromhout, Michelle C. Turner-, Anjoeka Pronk, Vivi Schlünssen

Abstract

Objective: Chemical occupational exposures are established risk factors for chronic obstructive pulmonary disease (COPD), but most evidence comes from studies that overlook the potential impact of multiple co-exposures. The occupational exposome framework addresses this by capturing a broad range of occupational exposures across a career. We aimed to explore the association between the occupational exposome and COPD risk.

Material and Methods: We included individuals aged ≥40 years without COPD at baseline from four registry-based cohort studies: the Danish Occupational Cohort with eXposure data (DOC*X), the Swedish National Cohort on Work and Health (SNOW), the State of Labor Force in Finland (SLFF) cohort, and the Norwegian Nor-Work cohort. Participants were followed from cohort-specific start years between 1960 and 1990 through to 2022. Occupational histories were coded using the European version of the International Standard Classification of Occupations 1988 (ISCO-88 (COM)). Cumulative exposures were assigned via job-exposure matrices (EuroJEM, OAsJEM, Endo-JEM, ALOHA+ JEM, and DOM-JEM), collectively covering 52 chemical, psychosocial, and ergonomic factors. Incident COPD was identified from hospital records with a primary or secondary diagnosis of COPD (ICD-10 code J44) or emphysema (J43). In the ExWAS analysis, we used discrete-time hazard models to assess associations between individual exposures and incident COPD. Model 1 was adjusted for age, sex, and smoking status; model 2 included additional adjustment for education. These were followed by mutually adjusted LASSO regression to identify the most relevant exposures.

Results: Analyses are ongoing and are expected to reveal individual occupational exposures and co-exposure patterns associated with increased COPD risk.

Conclusion: This study is expected to improve our understanding of how complex occupational exposure patterns across working-life relate to COPD risk, offering insights that may inform future prevention strategies.

Charlotte Juul Nilsson, Anne Helene Garde, Kirsten Nabe-Nielsen

Abstract

Objective Job demands in hospital environments may vary across shifts and work schedules. Identifying where demands are highest can help guide targeted prevention to reduce work strain and schedule-specific health risks. This study examined how perceived job demands differ by shift type and work schedule.

Material and Methods We used data from 966 employees in the 1001 nights-cohort – a study of female hospital workers in Denmark. Participants completed a baseline questionnaire and daily reports on working hours and physical, quantitative, and emotional demands (scale: 1–10). Analyses included participants with complete data on exposures and key covariates (age, education, Major Depression Inventory score, BMI, and shift duration). Mixed-effects models estimated differences in mean job demands across shift types (day or night) and work schedule-groups (permanent day, 2-shift without night, 2- or 3-shift with night, permanent night). Within-person analyses included participants with both day and night shift data.

Results On day shifts, 2-shift workers without night and 2- or 3-shift workers with night reported higher job demands compared to permanent day workers. The largest difference was observed in physical demands (+1.32, 95% CI: 0.93 to 1.71) among 2-shift workers without night. On night shifts, no differences were observed between permanent night workers and 2- or 3-shift workers. Within-person comparisons showed that night shifts were perceived as less demanding – both quantitatively (-0.28, 95% CI: -0.42 to -0.13) and emotionally (-0.51, 95% CI: -0.65 to -0.37) – than day shifts.

Conclusion 2- or 3-shift workers – with and without night – reported higher job demands on day shifts. Preventive measures may be more effective if tailored to specific shifts and work schedules. Further research should investigate whether differences in perceived job demands reflect actual job demands or are influenced by shift-related fatigue.

Florencia Harari, Klara Midander, Anneli Julander, Sandra Johannesson

Abstract

Objective: Lithium-ion batteries (LiB) are essential for electrification needed to achieve the climate goals, thus large-scale LiB manufacturing and recycling facilities are emerging globally. This pilot study aimed at characterizing metal exposure through air, skin and biomonitoring at a new recycling facility of LiB from electric vehicles.

Material and methods: Biomonitoring (blood, plasma and urine) was performed in 16 employees at two time points: baseline (before start of production) and follow-up (four months later). Among these, five workers (from separation and sorting n=3, storage n=1, and maintenance n=1) were selected to perform exposure assessment through air using personal air samplers for inhalable dust, through skin by acid-wipe sampling, and biomonitoring (pre- and post-shift and pre-shift one day later). All samples were analyzed for lithium, nickel and cobalt, by inductively coupled plasma mass spectrometry.

Results: Airborne metal concentrations exceeded occupational exposure limits for all three workers in separation and sorting (work-shift averages, in µg/m3: lithium 17-78, nickel 85-351, cobalt 25-117). Direct reading particle instruments showed high peak exposures of dust during specific work tasks. Inhalable metal concentrations were low among storage and maintenance workers. Nickel (0.002-0.3 µg/cm2) and cobalt (0.001-0.1 µg/cm2) were detected on the hands of the five workers. Among the 16 workers, metal concentrations in blood, plasma and urine were low, similar to those found in the general population.

Conclusion: Low metal concentrations in biological samples among workers in sorting and separation, where metal dust was elevated, suggest effective use of powered air purifying respirators. Sensitizing metals were detected on skin of all workers, in some cases at ranges that trigger eczema in sensitized individuals. Efforts to reduce metal emissions at the sources are needed.

Rikke Harmsen , Jakob Møller Hansen , Dagfinn Matre , Anne Emily Saunte Fiehn Arup , Anne Helene Garde

Abstract

Objective To investigate the prevalence of headaches on days with night shifts compared with day shifts within the same individuals, accounting for work-related psychosocial stressors, physical job demands, and sleep duration and quality. This approach aimed to isolate the impact of circadian misalignment due to night work from other potential headache triggers.

Material and Methods We used data from the 1001 nights-cohort, comprising female employees from the Danish hospital sector. Participants completed 14-day diaries, providing daily information on working hours, sleep, emotional job demands, quantitative job demands, physical job demands, and headache occurrence (yes/no). Participants with data from at least one day shift and one night shift were included. In total, 522 participants contributed 3,348 measurement days (1,926 day shifts and 1,422 night shifts). We estimated prevalence ratios (PRs) for headache occurrence, accounting for repeated measures within individuals.

Results Headaches were reported on 21.5% of days with day shifts and 27.9% of days with night shifts. Night shifts were associated with a significantly higher headache prevalence (PR: 1.32; 95% CI: 1.15–1.51) compared with day shifts, independent of work-related psychosocial stressors, physical job demands, or sleep characteristics. Among consecutive night shifts, the second night showed the highest headache prevalence (PR: 1.20; 95% CI: 1.03–1.40), using the first night as the reference.

Conclusion This is the first study to assess headache occurrence on days with night shifts versus day shifts while accounting for both job-related and sleep-related factors. Neither work-related psychosocial stressors, physical job demands, nor sleep parameters explained the higher headache prevalence. These findings suggest that other mechanisms related to night work-induced circadian misalignment may be key drivers of headache risk in night shift workers. Funding The present study was funded by the Danish Working Environment Research Fund.

Esben Meulengracht Flachs, Regitze Sølling Wils, Ingrid Sivesind Mehlum, Jens Peter Ellekilde Bonde, Astrid Juhl Andersen, Hannah Nørtoft Frankel, Sandra Søgaard Tøttenborg, Karin Sørig Hougaard, Camilla Sandal Sejbaek

Abstract

Objectives To describe absence during pregnancy in the Danish workforce according to occupation, industry, and changes over time (1998-2018).

Methods The Danish register-based cohort DOC*X-Generation was used to identify all pregnancies among women (18-50 years) engaged in regular employment in Denmark from 1998 to 2018. The cohort holds individual-level data on occupations coded according to the Danish versions of the International Standard Classification of Occupations and of EU’s nomenclature, NACE rev. 2. Data on absence from work was retrieved from the Danish Register for Evaluation and Marginalization. The study population comprised 884,616 pregnancies in 547,870 women.

Results In 48% of the included pregnancies, the women had at least one week with registered absence with a median of eight weeks with absence (5-95% percentile; 1-27 weeks). The highest proportion of pregnancies with absence was observed among painters (75%) and women in the manufacture of meat products industry (68%). The lowest proportions were seen among professionals (physics, mathematics, engineering, architecture, 30%) and in the research and university education industry (32%). The difference between the lowest and highest number of cumulated weeks with absence was 9 weeks (5 to 14). From 1998-2018 the proportion of pregnancies with registered absence decreased, whereas the extent of absence per pregnancy increased.

Conclusions Absence during pregnancy was consistently high over time, but with vast differences across occupations and industries. A deeper understanding of underlying reasons for pregnancy-related absence is essential to develop targeted strategies for reducing absence, such as providing better opportunities for early adjustments or other tailored interventions.

Susanne Strohmaier; Magdalena Żebrowska; Tianyi Huang; Kyriaki Papantoniou; Susan Redline; Richa Saxena; Martin K Rutter, Eva Schernhammer

Abstract

Aims Non-standard work schedules are becoming increasingly prevalent, with one in five workers participating in night shifts. Whether working night shifts is associated with cardiovascular-kidney-metabolic (CKM) outcomes, and whether chronotype or sleep duration modify this association, remains unclear.

Methods We utilized data from 96,365 UK Biobank participants (57% female, mean age 62 years), with information on employment history and tracked incidence of CKM (including cardiovascular diseases, chronic kidney diseases and/or type 2 diabetes) through 2022. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CIs), adjusting for a range of potential confounding factors.

Results Based on 5,967 incident CKM cases, participants with more than 20 years of night shift work history had a significantly higher rate of CKM (HR=1.32 [95% CI, 1.20-1.45]) compared to day workers, after adjusting for sex, age, ethnicity, and socioeconomic factors. Elevated rates were also observed among those working 8 or more night shifts per month (HR=1.32 [95% CI, 1.21-1.43]) and those with over 1,200 lifetime night shifts (HR=1.36 [95% CI, 1.25-1.48]) as compared to day workers; all Ptrend<0.001. The association between night shift work and CKM risk was significantly modified by sleep duration, with higher rates among short sleepers (<7 hours/night;Pinteraction= 0.009, 0.031, and 0.017 for night shift work duration, intensity, and cumulative number of nights worked, respectively). However, chronotype did not significantly modify this association.

Conclusion Our findings reveal a dose-response relationship between night shift work and CKM disease, which is further amplified by short sleep duration. Future studies should consider using CKM conditions as a composite outcome and investigate further how various sleep characteristics may modify the impact of night shift work.

Annett Dalbøge, Jens Peter Ellekilde Bonde, Anne Helene Garde, Johnni Hansen, Åse Marie Hansen, Ann Dyreborg Larsen, Sadie Costello, Morten Böttcher, Morten Fenger-Grøn, Henrik Albert Kolstad

Abstract

Objective To examine the exposure-response relations between cumulative evening and night shifts and incident myocardial infarction among hospital employed health care workers, including nurses, physicians, and others.

Materials and methods This national register-based cohort study includes all newly hired health care workers ever working evening or night shifts with day by day payroll information on evening and night shifts, from 2008/2009 to 2020. In total, we included 137 184 health care workers (mean age 33.3 years at inclusion, 77% women) who were followed from first registered evening or night shift for an average of 6.4 years. First time hospital contacts for myocardial infarction were identified in national health registers. Incidence rates of myocardial infarction by cumulative evening and night shifts were estimated by Poisson regression adjusted for sex, age, calendar year, diabetes, obesity, hypertension, hypercholesterolemia, education, and family history of cardiovascular disease; and for a subset of 13 080 workers, additionally adjusted for self-reported smoking, body mass index, and alcohol consumption.

Results During follow-up, 477 workers (49% women) were diagnosed with myocardial infarction. Men and women showed overall incidence rates of 12.5 and 3.4 per 10 000 person years. No increasing incidence rates of myocardial infarction with cumulative number of evening or night shifts were observed.

Conclusions This study of health care workers found no exposure-response relation between cumulative evening or night shifts and incident myocardial infarction during up to 13 years after the first recorded evening or night shift.