Social Jetlag Linked to Increased Cardiovascular Risk in Shift Workers

Circadian misalignment is associated with a high cardiovascular risk among shift workers: Interview with:

Sara Gamboa Madeira Medical Doctor - General & Family Physician PhD Student - EnviHealth&Co - Faculty of Medicine Lisbon University

Dr. Gamboa Madeira

Sara Gamboa Madeira
Medical Doctor – General & Family Physician
PhD Student – EnviHealth&Co – Faculty of Medicine
Lisbon University What is the background for this study?

Response: One in every five employees work in shifts across Europe1. Shift work have been associated with an increased risk for several cardiovascular diseases2 and three main mechanism have been proposed: unhealthy behaviours, disturbed sleep, and circadian misalignment.

This study focused on the role of circadian misalignment, which we assessed via social jetlag. Social jetlag is calculated using the Munich Chronotype Questionnaire3 by the difference between sleep behaviour on free-days (mainly driven by the individual “biological clock”, also called chronotype) and sleep behaviour on workdays (mainly drive by the “social clock”, namely work schedules). Chronotype is an individual feature which ranges from early/morning people to late/evening people (from proverbial lark to owls), with the majority of the population falling in between as a Gaussian distribution. Therefore higher levels of social jetlag mean a greater mismatch between what your biological clock need (e.g. go to sleep at 9pm) and what your social obligations impose on you (e.g. work until midnight). What are the main findings?

Response: Among a population of 300 blue-collar workers performing fixed shifts, we found that higher levels of social jetlag were significantly associated with a greater prevalence of smoking, hypertension and high cardiovascular relative risk (relative SCORE chart ≥3). We also found that the odds of being in the high cardiovascular risk group increased by 31% for each additional hour of social jetlag, even after adjusting for sociodemographic, lifestyle, occupational, and sleep characteristics in a multivariate analysis. What should readers take away from your report?

Response: These results add to the growing evidence that circadian misalignment may explain, at least in part, the association found between shift work and negative health outcomes. These findings suggest that assessing individual chronotype could guide employers to allocate each worker to their best timing for work, especially among atypical work schedules or, at least, to avoid the most detrimental shift among extreme chronotypes (e.g., an extreme early chronotype in late evening shifts or a late chronotype allocated to early morning shifts). What recommendations do you have for future research as a result of this study?

Response: Our findings suggest that sleep and circadian features, such as chronotype and social jetlag, should be included in future studies evaluating cardiovascular health, especially among the working population. We need both interventional and longitudinal studies to properly assess the potential impact of reducing social jetlag, meaning if late chronotypes cope better with late evening shifts and/or earlier chronotypes to early morning schedules, both psychologically and physiologically. Is there anything else you would like to add?

Response: The scientific paper will be published soon in open access on the Journal of sleep research.

Any disclosures?

Response: This work was supported by the Envihealth&Co PhD programme on Environmental Health co‑funded by the Fundação para a Ciência e a Tecnologia (FCT) and by companies associated with the programme (research grant PDE/BDE/127787/2016).

1 Eurofound Sixth European Working Conditions Survey – Overview report (2017 update). , Luxembourg , 2017. DOI: 10.2806/422172

2 Rivera, A.S., Akanbi, M., O’Dwyer, L.C., McHugh, M. Shift work and long work hours and their association with chronic health conditions: A systematic review of systematic reviews with meta-analyses. PLoS One, 2020, 15: e0231037. DOI: 10.1371/journal.pone.0231037

3 Roenneberg, T., Pilz, L.K., Zerbini, G., Winnebeck, E.C. Chronotype and social jetlag: A (self-) critical review. Biology (Basel)., 2019, 8: 1–19. DOI: 10.3390/biology8030054


ESC Preventive Cardiology 2021 online presentation:

Circadian misalignment is associated with a high cardiovascular risk among shift workers: is this an opportunity for prevention in occupational settings?



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Last Updated on April 27, 2021 by Marie Benz MD FAAD