Fifty years of research in the Scandinavian Journal of Work, Environment & Health

Changing of the guards at the Scandinavian Journal of Work, Environment & Health

With the first quarter of the 21st century in the books and the first issue of the year of the Journal in front of you, we would like to use this opportunity to wish all our readers, authors and reviewers a happy and healthy New Year. May your wishes, aspirations, and resolutions for 2025 come true.

One of the main challenges for the second quarter of the 21st century is the current and upcoming mass retirement of the baby boomer generation that is occurring in many countries, including and in particular in Europe (1). Numerous papers in the Journal have discussed the challenges and possible remedies (2–4). And now, the retirement of the boomers is also happening at SJWEH. As the New Year starts, we are saying goodbye to two Associate Editors as well as one Editor-in-Chief while saying hello to a new one.

The Associate Editors – Jens Peter Bonde and Mikko Härmä – are riding off into the sunset after decades-long service to the journal. Mikko has been with the Journal for more 30 years. He is a distinguished scholar in working time research and the effects of working time arrangements on workers’ health, which has evolved as a key topic in occupational health and SJWEH (5). Mikko joined the Journal as an Assistant-Editor-in-Chief in 1994 and became Editor-in-Chief in 2000, when the Journal’s inaugural Editor-in-Chief, Sven Hernberg, retired. For 20 years, Mikko was at the helm and steered the Journal towards its current position as one of the internationally leading occupational health journals. He recently reflected on this process in a presentation on the “changing business of running a scientific journal”, which is available on the Journal’s home page (6). At the end of 2019, Mikko stepped down as Editor-in-Chief, but remained on the Editorial Board as an Associate Editor, a position from which he is now retiring. Jens Peter has served as an Associate Editor since 2010. As an occupational physician and distinguished occupational epidemiologist, he had published extensively on a broad range of topics, including but not limited to reproductive health, cardiovascular disease, musculoskeletal disorders, mental disorders, and, most recently, COVID-19. For a research journal, it is stroke of luck to have a scholar with such a broad expertise on the Editorial Board, who can be assigned to a large proportion of the submitted papers. On a personal level, I would like to add that I am very grateful to Jens Peter for the many discussions we had on the methodological challenges in studying the health effects of psychosocial working conditions. These discussions influenced my research quite a bit.

The third retirement is that of Alex (Lex) Burdorf. Lex joined SJWEH as an Associate Editor in 2006 and became Co-Editor-in-Chief at the end of 2018, first together with Mikko Härmä and then with me. As an occupational hygienist and public health researcher, Lex is known for his seminal contributions to exposure assessment methods, musculoskeletal disorders, working-life expectancy and labor market participation, and causal inference debates. Sharing the Editor-in-Chief position with Lex for the past five years has been a privilege. It was educational, effective and, last but not least, a lot of fun. Fortunately for the Journal, Lex will stay on as an Associate Editor.

After saying all these goodbyes, we can also say one hello. Join me in welcoming Annina Ropponen, professor at the Finnish Institute of Occupational Health, who has been an Associate Editor at the Journal since 2018, as our new Co-Editor-in-Chief. Annina’s research covers a broad area in occupational health and includes, among other things, research on musculoskeletal disorders, working hours, shift work, remote work, sustainable employment, and sickness absence. I am very happy that Annina agreed to take on this new role and am very much looking forward to working together on the future for the Journal.

As we turn the page on this remarkable chapter and embrace the changes ahead, we remain deeply grateful for the invaluable contributions of our retiring editors and are excited to welcome new leadership. With this blend of continuity and fresh perspectives, we are confident that the Journal will continue to thrive as a leading voice in occupational health research. Here’s to building on our legacy and shaping an even brighter future together—thank you for being part of this journey.

References 1. European Commision. 2024 Ageing Report. Economic and Budgetary Projections for the EU Member States (2022-2070). Institutional Paper 279. Luxembourg: Publications Office of the European Union; 2024. Available from: https://economy-finance.ec.europa.eu/ecfin-publications_en. (Accessed: 10 December 2024). 2. Andersen LL, Calatayud J, Núñez-Cortés R, Polo-López A, López-Bueno R. Facilitators and barriers for working beyond statutory pension age: A prospective cohort study across 26 European countries. Scand J Work Environ Health. 2024;50(8):622-630. https://doi.org/10.5271/sjweh.4189 3. van der Mark-Reeuwijk KG, Weggemans RM, Bültmann U, Burdorf A, Deeg DJ, Geuskens GA, et al. Health and prolonging working lives: an advisory report of the Health Council of The Netherlands. Scand J Work Environ Health. 2019;45(5):514-519. https://doi.org/10.5271/sjweh.3828 4. Hasting RL, Mehlum IS, Undem K, Robroek SJW, Burdorf A, Gran JM, et al. The effects of a national, voluntary agreement for a more inclusive working life on work participation following long-term sickness absence: a Norwegian cohort study. Scand J Work Environ Health. 2023;49(7):466-476. https://doi.org/10.5271/sjweh.4112 5. Burdorf A, Rugulies R. Fifty years of research in the Scandinavian Journal of Work, Environment & Health. Scand J Work Environ Health. 2024;50(1):3-10. https://doi.org/10.5271/sjweh.4135 6. Härma M. The changing business of running a scientific journal - reflections on the SJWEH. Recording of a presentation held on 4 October 2024. Available from: https://www.sjweh.fi/index.php?page=50y. (Accessed: 10 December 2024).

Towards the year 2049: The next 25 years of occupational health and safety research

OBJECTIVE

In this discussion paper, we close our 2024 series reflecting on the successes, failures, and promises of occupational health and safety research in celebration of the 50th anniversary of the Scandinavian Journal of Work, Environment & Health (SJWEH). This paper aims to elaborate on the future of our research field.

METHODS

We conducted a narrative review of lessons learned in the series, examining insights gained and key takeaways. Additionally, we explored the current and anticipated agendas of major institutions, including the World Health Organization and the European Union, on occupational health and safety, as well as potential developments in the academic publishing industry.

RESULTS

Occupational health and safety research has significantly evolved over the last 50 years, emphasizing longitudinal study designs, enriching observational data with registry-based information, and expanding the scope of hazardous determinants impacting workers` health. Novel statistical approaches have further enabled researchers to address complex associations, such as mediation effects, and to strengthen causal inference in observational studies. At the same time, the publishing business is changing rapidly, with artificial intelligence poised to reshape both research practices and the landscape of academic publishing.

CONCLUSION

In the changing landscape of research and academic publishing, our goal is for SJWEH to continue to be a leading source of high-quality research dedicated to protecting and improving workers' health. We are curious and excited to see where all these current and anticipated changes will lead in the years to come.

When will we have enough evidence to require improvements at the workplace?

The need for evidence-based improvements at the workplace Work is an important social determinant of health (1). Decades of research on a wide range of different types of exposure, such as chemical, physical, biological, and psychosocial exposures at the workplace, has shown how poor working conditions are associated with adverse health outcomes and disparities in health. This has been well illustrated in the 2024 Discussion Paper series celebrating `50 years of research` in the Scandinavian Journal of Work, Environment & Health (2–9). With this rapidly increasing body of knowledge, it is quite disappointing to note that the increasing number of high-quality studies on identifying occupational risk factors are not matched by a similar number of high-quality studies aimed to design and evaluate measures that promote workers’ health and prevent work-related disease and disability (2).

There is a scarcity of evidence-based workplace interventions that can guide appropriate workplace policies, programs, and practices. A linked issue is that, in situations when sufficient evidence seems available, there is a lack of urgency in utilizing research findings in the practice of occupational safety and health (OSH). A European Union report argued that, in order for research to have an impact on workers’ safety and health, there is a great need to improve the translation of OSH research findings into practice, both in the occupational health services and at workplaces (10).

Both the lack of evidence-based guidance for healthy and safe workplaces as well as lack of implementation of available knowledge in practice can be partly attributed to the complexity of the workplace, given its multiple organizational levels, variety of settings and contextual factors, and required level of flexibility and adaptivity of interventions in order to be successful (11). Complex interventions require different research strategies, shifting the focus from the traditional binary question of effectiveness of a precisely defined intervention towards a broader understanding of mechanisms, processes, and outcomes of relevance to workers, companies, and OSH professionals (12).

Rise and demise of the RCT Many researchers have been trained that randomized controlled trials (RCT) provide the most rigorous evidence on beneficial effects of preventive, diagnostic, and therapeutic interventions (13). With the rise of the evidence-based medicine approach, the RCT design became the gold standard, demonstrating with high quality and reliability the causal effects of the intervention. In the past 40 years, this gold standard has increasingly been critiqued and – in the era of complex system thinking and complex interventions – the status of the RCT is eroding (13,14). There is strong evidence that if evidence-based health care is limited to RCT, the evidence will favor individual-based over multicomponent interventions, highly standardized simple interventions over complex ones, and short- over long-term interventions (14).

In occupational health, it has long been acknowledged that interventions often have an organizational or work environment context that hampers – or even excludes the possibility of – individual-level randomization and also makes cluster randomization very difficult (15). Very successful interventions in occupational health, eg, the introduction of a complete ban on asbestos (3) and the substitution of organic solvents in paints (4), would not have happened if knowledge from an RCT would have been the required level of evidence.

Alternative study designs and research methods In recent years, there has been a big debate around which study designs are needed for a valid interpretation of an intervention`s effects. At the heart of the discussion is the inherent trade-off between causal estimation of an intervention effect and estimation of an intervention effect that matters for practice. Opinions remain strongly divided.

Some researchers claim that observational studies will always be affected by bias and, thus, causal evidence can only be derived from experiments or trails emulated in observational studies (16). An experiment with randomization ensures exchangeability in that both groups are comparable for all known and unknown factors and, thus, these factors cannot bias the intervention effect. In the absence of an RCT, researchers have applied the ‘experimental causal inference’ framework to particular situations that may be interpreted as happening at random. These so-called `natural experiments` have specific statistical methods that try to ensure that the intervention of interest can be interpreted as an exogenous source (17). These natural experiment approaches include, among others, methods such as propensity-score matching, difference-in-differences, interrupted time series, instrumental variables, and regression discontinuity. An illustrative example is the introduction of a new nationwide graded return-to-work program whereby propensity-score matching demonstrated an increasing labor force participation and reduced permanent disability as a result of this intervention (18). Laaksonen and colleagues (19) used the regression discontinuity approach to show that vocational rehabilitation, assigned based on a threshold in earnings in past few years, increased paid employment, but results were far from being statistically significant. A difference-in-differences approach comparing trends before and after the introduction of a work reintegration program demonstrated reductions in the number of disability days, most notably among longer duration episodes (20). Jan Vandenbroucke and colleagues (21) have eloquently criticized this ‘causal inference’ movement, stating that truly natural experiments are rare and those that happen are usually not widely generalizable. Hence, complete reliance on natural experiments and linked statistical methods will limit much needed evidence in occupational health tremendously (22).

On the other side of the spectrum, researchers argue for a paradigm shift towards more practice-relevant evidence with a system lens on multiple factors that interact in dynamic and unpredictable ways in the complex world of real data (23, 24). It is proposed to determine whether an intervention contributes, along with other factors, to a desirable outcome, acknowledging that multiple components of the intervention might each contribute to an overall beneficial effect through heterogeneous effects on disparate causal pathways (23). Such a question can often not be answered by a specific research design, but requires a myriad of new types of data, analytical methods, and interdisciplinary work (24). It will be of interest to see in the next few years whether the ‘experimentalists’ and the ‘system thinkers’ can bridge the huge gap in their appreciation of what is considered solid evidence.

When is evidence strong enough to take action? Societal impact of our research requires research that matters, ie, research that provides compelling arguments to implement specific improvements in order to contribute to the health and wealth of workers and communities. Working longer in good health is an example of a key societal challenges in many countries (25), and, thus, researchers in occupational health are in the fortunate position to create societal impact by identifying determinants of healthy working-life expectancy and designing interventions that promote working longer in good health. However, this requires that scientific scrutiny for valid results does not result in postponing highly needed programs and policies in the workplace.

Several articles celebrating `50 years of research` in the Journal have documented that some preventive measures have been delayed unnecessarily, sometimes in a deliberate strategy by industry to manufacture uncertainty (4, 26). Delays in taking necessary action can also be the result of scientists hesitating too long about the correct interpretation of results. A classic example is the infamous crocidolite-chrysotile asbestos debate during the 1980s and 1990s, whereby proponents of the `chrysotile is safe` argument delayed the ban on asbestos (3). In an earlier editorial, we have argued that causal inference considerations should hamper neither development nor implementation of evidence-based recommendations in occupational health when the evidence-base is reasonable (27).

There are no golden rules to determine when our knowledge is sufficient to require preventive measures. I can only refer to the wise words of Sir Bradford Hill in his seminal address to the Royal Society of Medicine, describing the purpose of the newly-founded section of occupational medicine: “All scientific work is incomplete—whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have or to postpone action that it appears to demand at a given time (28)."

With these words in mind, we look forward to research that provides compelling information on how to tackle the current challenges in occupational health and studies that document how this knowledge has guided successfully preventive measures at the workplace. Hopefully, we can redress the imbalance between risk-oriented research and intervention studies and create a long-lasting positive societal impact on workers’ health.

References

1. Frank J, Mustard C, Smith P, et al. Work as a social determinant of health in high-income countries: past, present, and future. Lancet 2023;402:1357-67. https://doi.org/10.1016/S0140-6736(23)00871-1  2. Burdorf A, Rugulies R. Fifty years of research in the Scandinavian Journal of Work, Environment & Health. Scand J Work Environ Health 2024;50:3-10. https://doi.org/10.5271/sjweh.4135  3. Järvholm B, Burdorf A. Asbestos and disease - a public health success story? Scand J Work Environ Health 2024;50:53-60. https://doi.org/10.5271/sjweh.4146  4. Albin M, Johanson G, Hogstedt C. Successful prevention of organic solvent induced disorders: history and lessons. Scand J Work Environ Health 2024;50:135-41. https://doi.org/10.5271/sjweh.4155  5. Härmä M, Kecklund G, Tucker P. Working hours and health - key research topics in the past and future. Scand J Work Environ Health 2024;50:233-43. https://doi.org/10.5271/sjweh.4157  6. Kuijer PPFM, van der Wilk S, Evanoff B, Viikari-Juntura E, Coenen P. What have we learned about risk assessment and interventions to prevent work-related musculoskeletal disorders and support work participation? Scand J Work Environ Health 2024;50:317-28. https://doi.org/10.5271/sjweh.4172  7. Boot CRL, LaMontagne AD, Madsen IEH. Fifty years of research on psychosocial working conditions and health: From promise to practice. Scand J Work Environ Health 2024;50:395-405. https://doi.org/10.5271/sjweh.4180  8. Turner MC, Straif K, Kogevinas M, Schubauer-Berigan MK. Five decades of occupational cancer epidemiology. Scand J Work Environ Health 2024;50:489-502. https://doi.org/10.5271/sjweh.4190  9. Ropponen A, Rugulies R, Burdorf A. Towards the year 2049. The next 25 years of years of occupational health and safety research. Scand J Work Environ Health 2024;50(8):581-587. https://doi.org/10.5271/sjweh.4136  10. European Agency for Safety and Health at Work (EU-OSHA). Priorities for Occupational Safety and Health Research in Europe for the Years 2013-2020. Luxembourg: Publications Office of the European Union, 2014.  11. Skivington K, Matthews L, Simpson SA, et al. A new framework for developing and evaluating complex interventions: update of Medical Research Council guidance. BMJ 2021;374:n2061. https://doi.org/10.1136/bmj.n2061  12. Raine R, Fitzpatrick R, de Pury J. Challenges, solutions and future directions in evaluative research. J Health Serv Res Policy 2016;21:215-6. https://doi.org/10.1177/1355819616664495  13. Jones DS, Podolsky SH. The history and fate of the gold standard. Lancet 2015;385:1502-3. https://doi.org/10.1016/S0140-6736(15)60742-5  14. Bothwell LE, Greene JA, Podolsky SH, et al. Assessing the Gold Standard - Lessons from the history of RCTs. N Eng J Med 2016;374:2175-81. https://doi.org/10.1056/NEJMms1604593  15. Schelvis RMC, Oude Hengel KM, Burdorf A, et al. Evaluation of occupational health interventions using a randomized controlled trial: challenges and alternative research designs. Scand J Work Environ Health 2015;41:491-503. https://doi.org/10.5271/sjweh.3505  16. Hernán MA. Methods of public health research - strengthening causal inference from observational data. N Engl J Med 2021;385:1345-8. https://doi.org/10.1056/NEJMp2113319  17. Craig P, Katikireddi SV, Leyland A, Popham F. Natural experiments: an overview of methods, approaches, and contributions to public health intervention research. Ann Rev Public Health 2017:38:39-56. https://doi.org/10.1146/annurev-publhealth-031816-044327  18. Bethge M. Effects of graded return-to-work: a propensity-score-matched analysis. Scand J Work Environ Health 2016;42:273-9. https://doi.org/10.5271/sjweh.3562  19. Laaksonen M, Ilmakunnas I, Tuominen S. The impact of vocational rehabilitation on employment outcomes: A regression discontinuity approach Scand J Work Environ Health 2022;48:498-506. https://doi.org/10.5271/sjweh.4038  20. Macpherson RA, He A, Amick III BC, Koehoorn M, McLeod CB. Evaluating effectiveness of an integrated return-to-work and vocational rehabilitation program on work disability duration in the construction sector. Scand J Work Environ Health 2022;48:229-38. https://doi.org/10.5271/sjweh.4006  21. Vandenbroucke JP, Broadbent A, Pearce N. Causality and causal inference in epidemiology: the need for a pluralistic approach. Int J Epidemiol 2016;45:1776-86. https://doi.org/10.1093/ije/dyv341  22. Pearce N, Lawlor DA. Causal inference - so much more than statistics. Int J Epidemiol 2016;45:1895-1903. https://doi.org/10.1093/ije/dyw328  23. Greenhalgh T. Will COVID-19 be evidence-based medicine’s nemesis? PLoS Med 2020;17:e1003266. https://doi.org/10.1371/journal.pmed.1003266  24. Rod NH, Broadbent A, Rod MH, et al. Complexity in epidemiology and public health. Addressing complex health problems through a mix of epidemiologic methods and data. Epidemiology 2023;34:505-14. https://doi.org/10.1097/EDE.0000000000001612  25. Burdorf A, Cassai Pereira Fernandes R, Robroek SJW. Health and inclusive labour force participation. Lancet 2023;402:1382-92. https://doi.org/10.1016/S0140-6736(23)00868-1  26. Michaels M, Monforton C. Manufacturing uncertainty: contested science and the protection of the public’s health and environment. Am J Public Health 2005;95(suppl 1):S39-48. https://doi.org/10.2105/AJPH.2004.043059  27. Rugulies R, Burdorf A. Causal inference and evidence-based recommendations in occupational health and safety research. Scand J Work Environ Health 2020;46:554-6. https://doi.org/10.5271/sjweh.3929 28. Hill AB. The environment and disease: association or causation? Proc. Royal Soc Med 1965;58:295-300. https://doi.org/10.1177/003591576505800503

Five decades of occupational cancer epidemiology

OBJECTIVE

In this discussion paper, we provide a narrative review of past and present occupational cancer studies in the journal with a viewpoint towards future occupational cancer research.

METHOD

We reviewed all references in the journal that mentioned cancer according to relevance to etiology, cancer type, agent type, study design, and study population.

RESULTS

The Scandinavian Journal of Work, Environment & Health has published over 300 manuscripts on occupational cancer over the 50 past years. Although studies of cancer represent the primary health outcome in the journal overall, the relative ranking of cancer manuscripts has declined somewhat over time. A large body of evidence from studies of occupation and industry was apparent both in early research and continuing in recent years. There are several examples of the utility of pooled multi-country collaborative studies. Studies also took advantage of available high-quality national population and cancer registers in Nordic countries. There have been notable shifts in focus with regard to the cancer types examined, with increases in publications examining female breast cancer over the decades. The interplay of studies of occupational and environmental cancer has also been apparent.

CONCLUSIONS

The journal offers a unique viewpoint to consider the evolution of occupational cancer evidence over time. Studies of occupational cancer have played a central role in global cancer hazard identification efforts. Although much has been gained, there remains a need for renewed global support for occupational cancer research. Concerted efforts will be needed to ensure a future robust evidence-base for occupational and environmental cancer worldwide.

Research topics in occupational medicine, 1990-2022: A text-mining-applied bibliometric study

OBJECTIVE

Occupational health has been influenced by societal and industrial changes. This study aimed to clarify topic trends in occupational health research in 1990-2022.

METHODS

We conducted a text-mining-adjusted bibliometric study using research titles in occupational health. Data on research titles and the years of publication were collected from 26 peer-reviewed journals on PubMed. Using morphological and correspondence analyses in text mining, we structured research topics into multiple categories and visualized the relationship between all categories and publication years. Statistical analyses were conducted using the text mining software - KH Coder 3.0.

RESULTS

We obtained 48 645 articles containing 714 890 words in their titles. The research topics were classified into 4 categories and 17 subcategories, of which those of occupations; countries; non-intervention; psychosocial factors; lifestyle factors; safety; symptoms; therapy and care; and productivity have recently shown an increasing trend. In contrast, the subcategories of risk, chemical factors, disease, and organ damage showed decreasing trends. Chemical factors, which were the main topics in the 1990s, included risk, organ damage, and disease. Productivity, the main topic in the 2020s, co-occurred with lifestyle factors, symptoms, and intervention.

CONCLUSIONS

Focal areas in occupational-health research shift according to societal trends. Occupational-health research has primarily analyzed issues in developed countries with capitalist values and may not have sufficiently covered issues in developing countries. It is imperative for policymakers and public funding bodies to determine priorities for investigation in the field.

Fifty years of research on psychosocial working conditions and health: From promise to practice

OBJECTIVE

This paper presents an overview of 50 years of research on psychosocial working conditions and health with regards to conceptualization, interventions and policy. We reflect on the promise of past and current research on psychosocial working conditions and, in addition, discuss current progress in translating this research into workplace practice and improvements in people's working lives.

METHODS

We conducted a narrative review of meta-reviews and key publications on psychosocial working conditions and health. The review covers a historical overview of theories of the past 50 years, measurement of psychosocial working conditions, health effects, intervention research, and policy development on psychosocial working conditions.

RESULTS

Psychosocial working conditions are conceptualized in different ways, with increasing complexity in the understanding developing over time. Exposures related to psychosocial working conditions are associated with a wide range of health outcomes, in particular cardiovascular disease and mental health conditions. In response to growing evidence on associations between psychosocial working conditions and health outcomes, intervention research has expanded rapidly, but for various reasons the evidence base is stronger and more extensive for individual- than organizational-level interventions. This individual/organizational imbalance is reflected in practice, and may partly explain why policy interventions have yet to show reductions in exposures to psychosocial work factors and associated adverse outcomes.

CONCLUSIONS

Pressing needs for advancing the field include improvements in capturing exposure dynamics, developing objective measures of exposure, methodologic advancements to optimize causal inference in etiologic studies, and alternatives to randomized controlled trials for intervention evaluation.

What have we learned about risk assessment and interventions to prevent work-related musculoskeletal disorders and support work participation?

OBJECTIVE

The Scandinavian Journal of Work, Environment & Health (SJWEH) was established half a century ago. This paper provides an overview of research on musculoskeletal disorders (MSD) published over these 50 years. Three themes are described: risk assessment, interventions to prevent work-related MSD, and interventions to support work participation. Finally, implications for future research are highlighted.

METHODS

A systematic literature search was performed for all papers on MSD published in SJWEH. Each paper was coded on several criteria including research topic, type of MSD, risk factor(s), and number of citations. Findings were tabulated, and discussions within the author team defined the main results and future research directions.

RESULTS

The search resulted in 1056 papers, of which 474 were included. The most reported-on MSD was low-back pain (LBP, 18%) and the most reported-on work-related risk factors were physically demanding work (14%) and psychosocial factors (12%). Research has contributed to improving case definitions, refining work-related exposure criteria, and recognizing the varying importance of physical and psychosocial factors across different MSD. Research on the association between work-related risk factors and LBP continues to emerge. Effective interventions for prevention of MSD are characterised by sufficient exposure reduction, while supporting work participation requires integrating health care, with multidisciplinary actions directed at factors involving the worker, employer, and workplace.

CONCLUSION

Research has provided valuable insights into risk assessment, interventions for preventing work-related MSD, and supporting work participation. Intervention studies remain warranted and new areas include adopting whole-system approaches to prevent work-related MSD and promoting the concept of musculoskeletal health.

Working hours and health - key research topics in the past and future

OBJECTIVE

This paper discusses the past and present highlights of working hours and health research and identifies key research needs for the future.

METHOD

We analyzed over 220 original articles and reviews on working hours and health in the Scandinavian Journal of Work, Environment & Health published during the last 50 years. Key publications from other journals were also included.

RESULTS

The majority of identified articles focussed on the effects of shift and night work, with fewer studying long and reduced working hours and work time control. We observed a transition from small-scale experimental and intensive field studies to large-scale epidemiological studies utilizing precise exposure assessment, reflecting the recent emergence of register-based datasets and the development of analytic methods and alternative study designs for randomized controlled designs. The cumulative findings provide convincing evidence that shift work and long working hours, which are often associated with night work and insufficient recovery, increase the risk of poor sleep and fatigue, sickness absence, occupational injuries, and several chronic health conditions such as cardiovascular diseases and cancer. The observed risks are strongly modified by individual and work-related factors.

CONCLUSIONS

Although the observed health risks of shift work and long working hours are mostly low or moderate, the widespread prevalence of exposure and the hazardousness of the many associated potential outcomes makes such working time arrangements major occupational health risks. Further research is needed to identify exposure-response associations, especially in relation to the chronic health effects, and to elucidate underlying pathways and effective personalized intervention strategies.

Working hours and cardiovascular disease

Working hours, including the number and the arrangement thereof – such as shift work, night work, and quick returns – are classic topics in research on work environment and health. The struggle for working time reduction and the eight-hour work day is also one of the oldest fights of the labor movement, dating back to the 19th century (1). International Workers’ Day, celebrated annually on 1 May, has its origin in the Haymarket Affair, a rally in support of a strike for the eight-hour work day at the Haymarket Square in Chicago, USA, on 4 May 1886. At the rally, a riot broke out and a bomb exploded, killing several workers and police officers. In the aftermath, the State of Illinois prosecuted labor movement activists. Although the person who throw the bomb was never identified and the circumstances of the attack remained unclear, four labor movement activists, including August Spies, the editor of the German-American newspaper Arbeiter-Zeitung, were executed by hanging on 11 November 1887. A fifth activist died by suicide in prison (2).

When the International Labour Organization (ILO) was established as an agency of the newly created League of Nations (the predecessor of today’s United Nations) after World War I in 1919, one of its main aims was the regulation and reduction of working time (1). The demand for the 8-hour work day and 48-hour work week was even included in the peace treaty of Versailles (Part XIII, Section II, Article 427) that was signed on 28 June 1919 following World War I (3, 4).

Although working hours have been greatly reduced in many high-income countries since the 19th century, particularly in Europe, the discussion about working hours remains topical, as can be seen by the recent debate about a 4-day working week (5, 6). In South-East and East Asian countries, such as Japan, South Korea, and Taiwan, where working hours >48 hours per week are still widely prevalent, health concerns of such long working hours are an important topic of discussion (7, 8). Notably, the Japanese language has coined two terms: karōshi for death due to overwork (usually of cardiovascular causes) and karōjisatsu for death by suicide due to overwork (9). At the Scandinavian Journal of Work, Environment & Health, we regularly receive papers from researchers in Asia examining the health effects of long working hours (10–12). This issue includes a paper from a German research group on the association between night shift work and risk of cardiovascular disease (13). I use this opportunity to reflect briefly in this editorial on research on working hours and cardiovascular health. In the May issue (number 4) of the Journal, as part of our 50-year anniversary special publication series (14, 15), there will be a much more detailed account on what we have learned so far on working hours and health.

Long working hours and cardiovascular disease In 2015, Kivimäki et al (16) published a seminal paper on long working hours and cardiovascular disease for the Individual Participant Data Meta-Analysis of Working Population (IPD-Work) Consortium that showed an association of long working hours with an increased risk of both ischemic heart disease and stroke (16). The association was stronger for stroke than ischemic heart disease (pooled relative risks 1.33 versus 1.13). Furthermore, for stroke, but not ischemic heart disease, the analyses suggested an exposure–response pattern. Thus, the longer the working hours, the greater the risk of stroke.

From 2017 to 2021, the World Health Organization (WHO) and ILO conducted a project on the WHO/ILO Joint Estimates of the Work-Related Burden of Disease and Injury (17, 18) that included systematic reviews on the association of long working hours and risk of ischemic heart disease (19) and stroke (20). Results were similar to those reported by the IPD-Work Consortium in 2015. Long working hours, defined as ≥55 hours per week, were associated with a small increased risk of ischemic heart disease (pooled risk ratio 1.17) (19) and a larger increased risk of stroke (pooled risk ratio 1.35) (20). Based on these risk estimates and estimates on the country-specific prevalence of long working hours, the WHO and ILO estimated that, in 2016, globally 745 194 deaths were attributable to long working hours, with the largest burden in South-East Asia (17, 18, 21). A summary of the WHO/ILO joint estimates project has been published as a discussion paper in our Journal (22), together with an editorial (23).

Obviously, the estimate of approximately 750 000 annual deaths due to long working hours is based on several assumptions, including that the epidemiological studies` estimates indicate a causal association between long working hours and cardiovascular outcomes and that data on the worldwide prevalence of long working hours are valid. Kivimäki and colleagues (24) expressed concerns about the interpretation that there is sufficient evidence for harmfulness of long working hours with regard to ischemic heart disease. Among other things, the authors were concerned about residual confounding (eg, by health-related behaviors, although it is debated whether they are mainly confounders, for which one should control, or mediators, for which one should not control (25)). They also presented analyses of data that suggested that socioeconomic position might be an important effect modifier and that the harmful effect of long working hours on risk of ischemic heart disease may be limited to workers of low socioeconomic position. As socioeconomic position is linked to the type of work the workers are doing, the possible effect modification by socioeconomic position could also mean that other, unmeasured working conditions may modify the association between long working hours and health. In other words, in addition to the length of the working hours, what happens during these working hours might also be important. In Denmark, Hannerz and colleagues (26, 27) attempted to replicate the analyses on long working hours and ischemic heart disease and stroke using large-scale register data. With regard to ischemic heart disease, they did not find an increased risk with long working hours [rate ratio (RR) 1.07, 95% confidence interval (CI) 0.94–1.21 for >48 versus 32–40 hours] (26). When stratified by socioeconomic position, long working hours were not associated with an increased risk of ischemic heart disease among workers of high, medium and unknown socioeconomic position, but there was an increased risk among workers of low socioeconomic position that worked long hours (RR 1.27, 95% CI 1.05–1.53). Although the interaction `long working hours × socioeconomic position` was not statistically significant, this increased risk among workers of low socioeconomic position is in agreement with the analyses by Kivimäki et al (24). With regard to stroke, Hannerz et al (27) did not find an increased risk for all types of stroke combined among those with long working hours, however, they reported an association between long working hours and increased risk of hemorrhagic stroke. This result was recently replicated in an analysis of the French CONSTANCES study (28) where exposure to long working hours during the past ten years was, in the adjusted model, associated with an increased risk of hemorrhagic stroke but not ischemic stroke.

One can summarize that during the past ten years, several large-scale studies and meta-analyses on long working hours and cardiovascular outcomes have been published. Whereas the WHO has concluded that there is sufficient evidence for harmfulness for the association between long working hours and ischemic heart disease and stroke (19–21), other studies point to possible effect modification by socioeconomic position (24, 26) with regard to ischemic heart disease and the need to distinguish between ischemic and hemorrhagic stroke (27, 28).

Shift work, night shift work and cardiovascular disease In 2018, Torquati et al (29) published a systematic review and meta-analysis that showed an increased risk of cardiovascular disease among shift workers. For those working shifts for five years, each additional five-year period of shift work was associated with a 7% increased risk of cardiovascular disease.

Night shift work has been of particular interest for cancer research (30) but might also be relevant with regard to cardiovascular diseases. In their recent review and meta-analysis, Su et al (31) reported that night shift work was associated with an increased risk of cardiovascular mortality (pooled estimate 1.15, 95% CI 1.03–1.29). However, only four studies were included in this review. In 2022, a Swedish research group published two papers on night shift work from a large sample of healthcare workers in Stockholm, one on cerebrovascular disease and the other on ischemic heart disease. Bigert et al (32) reported that frequent night shifts and frequent consecutive night shifts were associated with an increased risk of cerebrovascular disease, including stroke. Kader et al (33) reported that permanent night shifts and frequent night shifts were associated with an increased risk of ischemic heart disease. In Denmark, Vestergaard et al (34)examined the association between night shift work and ischemic heart disease in a large-cohort of healthcare workers with day-to-day payroll information. The results were less clear than those of Kader et al (33): male, but not female, healthcare workers with night work had an increased risk of ischemic heart disease compared to day-time workers. The paper by Jankowiak et al (13) in the current issue of the Journal examined night shift work and risk of cardiovascular disease in a population-based cohort in the city of Mainz and Mainz-Bingen in Germany (13). The hazard ratios for low, middle, and high night shift work were 1.19, 1.32, and 1.14, respectively, compared to no night shift work, in the most-adjusted model. An important strength of the study is the comprehensive clinical examination of the participants, both at baseline and follow-up. An important limitation is the very low number of cases in the exposure groups during the five-year follow-up. Unsurprisingly, the CI of all estimates were wide and included unity and, thus, were far away from being statistically significant. The uncertainty of the estimates do not allow firm conclusions on the results. However, the estimates from this study can be included in meta-analyses, which then may provide us with more insight on the role of night shift work on risk of cardiovascular disease.

Important challenges for future research on working time and cardiovascular disease will include better use of electronic working time registration systems that will allow a more precise measurement of exposure to long working hours and the frequency and type of shift work and night shift work (35, 36). It will also be important to conceptually clarify whether health behaviors that are hazardous to cardiovascular health – such as certain dietary patterns, lack of leisure time physical activity, or smoking – are confounders or mediators, or both, for the association between working time and cardiovascular disease. This clarification is key to correctly handling data on these health behaviors in the statistical models. Finally, examining the relations of the different working time arrangements with the contents of work conducted during these arrangements might be fruitful for a better understanding of the contribution of work to cardiovascular disease.

Conflict of interest statement Reiner Rugulies was involved in both the IPD-Work Consortium and the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury project. References 1. International Labour Organization (ILO). International Labour Standards on Working time [Website]. 2024. Available from: https://www.ilo.org/global/standards/subjects-covered-by-international-labour-standards/working-time/lang--en/index.htm. (Accessed: 26 Februar 2024). 2. Chicago Historical Society and the Trustees of Northwestern University. The dramas of Haymarket [Website]. 2000. Available from: https://www.chicagohistoryresources.org/dramas/. (Accessed: 26 February 2024). 3. Yale Law School. The Avalon Project: Documents in Law, History and Diplomay. The Versailles Treaty June 28, 1919: Part XIII [Website]. 2008. Available from: https://avalon.law.yale.edu/imt/partxiii.asp. (Accessed: 2 March 2024). 4. International Labour Office. Official Bulletin, Volume I, April 1919 - August 1920. 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New occupational threats to Japanese physicians: karoshi (death due to overwork) and karojisatsu (suicide due to overwork). Occup Environ Med. 2008;65(6):428-429. https://doi.org/10.1136/oem.2007.037473 10. Huang Y, Xiang Y, Zhou W, Li G, Zhao C, Zhang D, et al. Long working hours and all-cause mortality in China: A 26-year follow-up study. Scand J Work Environ Health. 2023;49(8):539-548. https://doi.org/10.5271/sjweh.4115 11. Lee DW, Choi J, Kim HR, Myong JP, Kang MY. Differential impact of working hours on unmet medical needs by income level: a longitudinal study of Korean workers. Scand J Work Environ Health. 2022;48(2):109-117. https://doi.org/10.5271/sjweh.3999 12. Lee W, Kang SK, Choi WJ. Effect of long work hours and shift work on high-sensitivity C-reactive protein levels among Korean workers. Scand J Work Environ Health. 2021;47(3):200-207. https://doi.org/10.5271/sjweh.3933 13. Jankowiak S, Rossnagel K, Bauer J, Schulz A, Liebers F, Latza U, et al. 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World Health Organization and International Labour Organization (WHO/ILO). Joint estimates of the work-related burden of disease and injury, 2000-2016: global monitoring report. Geneva: WHO/ILO; 2021. Available from: https://apps.who.int/iris/rest/bitstreams/1370920/retrieve. (Accessed: 25 March 2022). 18. World Health Organization and International Labour Organization (WHO/ILO). Joint estimates of the work-related burden of disease and injury, 2000-2016: technical report with data sources and methods. Geneva: WHO/ILO; 2021. Available from: https://apps.who.int/iris/rest/bitstreams/1370904/retrieve. (Accessed: 25 March 2022). 19. Li J, Pega F, Ujita Y, Brisson C, Clays E, Descatha A, et al. The effect of exposure to long working hours on ischaemic heart disease: A systematic review and meta-analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury. Environ Int. 2020;142:105739. https://doi.org/10.1016/j.envint.2020.105739 20. Descatha A, Sembajwe G, Pega F, Ujita Y, Baer M, Boccuni F, et al. The effect of exposure to long working hours on stroke: A systematic review and meta-analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury. Environ Int. 2020;142:105746. https://doi.org/10.1016/j.envint.2020.105746 21. Pega F, Náfrádi B, Momen NC, Ujita Y, Streicher KN, Prüss-Üstün AM, et al. Global, regional, and national burdens of ischemic heart disease and stroke attributable to exposure to long working hours for 194 countries, 2000-2016: A systematic analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury. Environ Int. 2021;154:106595. https://doi.org/10.1016/j.envint.2021.106595 22. Pega F, Hamzaoui H, Nafradi B, Momen NC. Global, regional and national burden of disease attributable to 19 selected occupational risk factors for 183 countries, 2000-2016: A systematic analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury. Scand J Work Environ Health. 2022;48(2):158-168. https://doi.org/10.5271/sjweh.4001  23. Coggon D. Estimating population burdens of occupational disease. Scand J Work Environ Health. 2022;48(2):83-85. https://doi.org/10.5271/sjweh.4007 24. Kivimäki M, Virtanen M, Nyberg ST, Batty GD. The WHO/ILO report on long working hours and ischaemic heart disease - Conclusions are not supported by the evidence. Environ Int. 2020;144:106048. https://doi.org/10.1016/j.envint.2020.106048 25. Li J, Rugulies R, Morgan RL, Woodruff T, Siegrist J, WHO/ILO Working Group of Individual Experts on Long Working Hours on Ischaemic Heart Disease. Systematic review and meta-analysis on exposure to long working hours and risk of ischaemic heart disease - Conclusions are supported by the evidence. Environ Int. 2020;144:106118. https://doi.org/10.1016/j.envint.2020.106118  26. Hannerz H, Larsen AD, Garde AH. Long weekly working hours and ischaemic heart disease: a follow-up study among 145 861 randomly selected workers in Denmark. BMJ Open. 2018;8(6):e019807. https://doi.org/10.1136/bmjopen-2017-019807 27. Hannerz H, Albertsen K, Burr H, Nielsen ML, Garde AH, Larsen AD, et al. Long working hours and stroke among employees in the general workforce of Denmark. Scand J Public Health. 2018;46(3):368-374. https://doi.org/10.1177/1403494817748264 28. Fadel M, Sembajwe G, Li J, Leclerc A, Pico F, Schnitzler A, et al. Association between prolonged exposure to long working hours and stroke subtypes in the CONSTANCES cohort. Occup Environ Med. 2023;80(4):196-201. https://doi.org/10.1136/oemed-2022-108656 29. Torquati L, Mielke GI, Brown WJ, Kolbe-Alexander T. Shift work and the risk of cardiovascular disease. A systematic review and meta-analysis including dose-response relationship. Scand J Work Environ Health. 2018;44(3):229-238. https://doi.org/10.5271/sjweh.3700 30. IARC Working Group on the Identification of Carcinogenic Hazards to Humans. Night shift work. Lyon, France: IARC; 2020. Available from: https://publications.iarc.fr/_publications/media/download/6397/c965a667eda3a390d9797cbcde59765fef9dcb7a.pdf. (Accessed: 29 February 2024). 31. Su F, Huang D, Wang H, Yang Z. Associations of shift work and night work with risk of all-cause, cardiovascular and cancer mortality: a meta-analysis of cohort studies. Sleep Med. 2021;86:90-98. https://doi.org/10.1016/j.sleep.2021.08.017 32. Bigert C, Kader M, Andersson T, Selander J, Bodin T, Gustavsson P, et al. Night and shift work and incidence of cerebrovascular disease - a prospective cohort study of healthcare employees in Stockholm. 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Vestergaard JM, Haug JND, Dalbøge A, Bonde JPE, Garde AH, Hansen J, et al. Validity of self-reported night shift work among women with and without breast cancer. Scand J Work Environ Health. 2024;50(3):152–157. https://doi.org/10.5271/sjweh.4142

The achievements and challenges of occupational health research: Looking back and ahead

With this first issue of 2024, we kick off the celebration of 50 years of publishing research in the Scandinavian Journal of Work, Environment & Health. In January 1975, the inaugural issue of the Journal was published (read it here: www.sjweh.fi/issue/274). We are delighted that 50 years later not only are we still around, but we have retained our special position in the science publication business as an independent journal that is not owned by a commercial publishing house. We are grateful that our not-for-profit publisher, the Nordic Association of Occupational Safety and Health (NOROSH), has ensured this independence. And we are proud to belong to a community of authors, reviewers, editors, international advisory board members, and, of course, readers that is committed to research excellence and has carried this journal for now half a century. Thank you!

We want to celebrate our anniversary by looking both back and ahead. In each issue of 2024, we will include an invited 50-year-anniversary article, authored by leading researchers in the field. In this first issue, we take a look at ourselves, reflecting on work environment exposures and health outcomes that have emerged as well as those that have vanished from the pages in the Journal. And we take a look at those papers that have generated the greatest interest among our readers (1).

In the coming year, various authors will take a look at the research field, that is, they will discuss specific work environment conditions and health outcomes. This will include exposures as diverse as asbestos and the psychosocial work environment and outcomes such as musculoskeletal disorders and occupational cancers. We will in particular examine the successes and failures with regard to these exposures and outcomes. Has occupational health research made a difference? Are there success stories where our research has helped to protect and improve workers’ health and thereby contributed to a better population health? Did we provide solid evidence on health hazardous, health-protecting, and health enhancing working conditions and did this result in changes at the workplace? Or did we fail? Was our research not good enough to provide sufficient evidence for action? Or was our research good enough but action still did not happen? And what can we do in the future to improve? How can we do research better and thus make a difference in society?

We are looking forward to the answers to these questions in the anniversary-related papers, which are incidently not yet written, so we do not know what they will tell us. Our guess is, though, that there are no easy answers and a lot of work still remains ahead of us. We and others have recently argued in a Discussion Paper series on “Work and Health” in The Lancet that “major gains in population health and reductions in health disparities can be made by an increased focus on improving the work environment.” (2). However, as we also argue in the series, there is still a long way to go in realizing the potential that good work has for better population health (2–4).

Our objective with 50-year SJWEH anniversary series is that, by the end of the year, the occupational health community will have become more knowledgeable about what went well and not so well in our research field and that we feel confident where to go next. To engage the community further in this discussion, we are planning a half-day in-person and online symposium on 4 October 2024. We are still working on the exact format and content of the symposium. Please stay tuned on LinkedIn and follow the updates in our newsletter.

References 1. Burdorf A, Rugulies R. Fifty years of research in the Scandinavian Journal of Work, Environment & Health. Scand J Work Environ Health. 2024;50(1):3–10. https://doi.org/10.5271/sjweh.4135 2. Frank J, Mustard C, Smith P, Siddiqi A, Cheng Y, Burdorf A, et al. Work as a social determinant of health in high-income countries: past, present, and future. Lancet. 2023;402(10410):1357-1367. https://doi.org/10.1016/S0140-6736(23)00871-1 3. Rugulies R, Aust B, Greiner BA, Arensman E, Kawakami N, LaMontagne AD, et al. Work-related causes of mental health conditions and interventions for their improvement in workplaces. Lancet. 2023;402(10410):1368-1381. https://doi.org/10.1016/S0140-6736(23)00869-3 4. Burdorf A, Fernandes RCP, Robroek SJW. Health and inclusive labour force participation. Lancet. 2023;402(10410):1382-1392. https://doi.org/10.1016/S0140-6736(23)00868-1