Shift work and cancer: Circadian disruption, epidemiological evidence and occupational disease criteria

Abstract

The health effects of shift and night work have been the subject of many scientific studies. The spectrum of possible diseases and endpoints associated with shift and night work range from chronic diseases, such as cancer and cardiovascular diseases, over sleep disorders and psychological stress up to reproductive disorders and accidents. In June 2019 the International Agency for Research on Cancer (IARC) classified night work as probably carcinogenic to humans (group 2A), thus confirming its previous assessment from 2007. The IARC expert group pointed out the continuing large heterogeneity of the study results. The majority of population-based case-control studies showed positive associations between shift work and cancer, whereas in many cohort studies no such associations were observed. Therefore, the question as to whether increased cancer risks can actually be attributed to shift or night work cannot yet be answered with certainty. This article provides an overview of open questions and aspects of shift work research using the example of cancer and discusses the current implications for occupational health.