Case study on night shift work

Experimental and epidemiological evidence shows that long-term disruption of endogenous circadian rhythms, in particular due to exposure to light during the biological night, may be associated with a wide range of common NCDs, including cancers, cardiovascular diseases and major metabolic disorders (obesity and type 2 diabetes). The prevalence of circadian disruption in human populations is high and increasing due to expanding human activities over the 24-hour day in both the working and the general population. The need of establishing the long-term impact of circadian disruption on health, the understanding of biological pathways and the application of population and individual prevention policies is a priority for health across all ages. In 2007, the International Agency for Research on Cancer (IARC/WHO) concluded that “shift work that involves circadian disruption is probably carcinogenic to humans”). This mainly based on animal experimental evidence with only limited human evidence on shift work and breast cancer. The public health consequences of this evaluation are important, since about 20% of the workforce in Europe is doing some non-standard work schedule. Individual chronotype is a human attribute with genetic basis that reflects the circadian phase of entrainment. Chronotype correlates with diurnal preference, an attribute reflecting personal preference for activities in the morning or evening. Diurnal preference and chronotype may affect shift work adaptation and evening types (subjects with a later circadian phase) may adapt faster to night shift work. Genetic variation, related to chronotype, may also affect adaptation and effects of circadian disruption on health. Circadian disruption may also affect behaviour and lifestyle and even other work-related factors  due to fatigue. These are, however, understudied areas of research limiting the prediction of individual risk and planning of prevention policies. This complex exposure situation involves both occupational and non-occupational risk factors and genetic make-up. There is a need for better insights in relevant exposure metrics and biological pathways, particularly relevant in the context exposome research. By complementing the evidence on shift work in the EPHOR mega cohort with state-of-the-art methods for assessing the external and internal exposome, we uniquely advanced knowledge on how the long-term and short-term occupational and non-occupational environment (including behaviour and lifestyle) interact with the genetic make-up of individuals, and disease risk and identify mechanistic pathways and potential gender differences. 

In this case study we investigated the effects of shift work on health by looking at short-term exposures. Effects of short-term exposures, in relation to the working life exposome, biological pathways, early markers of disease and key body functions were assessed using external and internal exposome data. The protocol used in this case study can be downloaded below. 

The EPHOR-NIGHT project investigated the biological, clinical, and psychosocial impacts of night shift work using an exposome approach. Conducted between 2022 and 2024, the study recruited 937 healthcare workers aged 20–65 from Spain, Sweden, Denmark, and the Netherlands. Participants were classified as permanent day workers (39%), rotating night shift workers (26%), and permanent night workers (35%). Using an integrated methodology—including questionnaires, wearable sensors, clinical assessments, and extensive multi-omics profiling (hormones, immune markers, DNA methylation, transcriptomics, proteomics, metabolomics, and gut microbiome)—the study examined the impact of night shift work across multiple health domains.

All data is updated to YODA, where they will be available until 2030. The data will be made available pseudoanonymized. Access to study data is possible through a completed data request form, available at (https://www.isglobal.org/en/-/ephor). Participants are required to adhere to the specified collaboration requirements namely include 2 participants per center where data are used from, no overlapping topics, relevant human subjects review, review by the steering committee. There will be minimal costs if data preparation is needed or if biological samples are requested.