Shiftwork: Health effects and interventions

Night-time shiftwork has been classified as ‘probably carcinogenic to humans’ by the International Agency for Research on Cancer and was identified as a research priority by Occupational Cancer Research Centre stakeholders. Approximately 18.5% of the working population in Canada, or nearly 2.8 million workers, work a regular evening shift, regular graveyard shift, or a rotating (both days and nights) shift. Understanding which industries employ shiftworkers and the types of shifts that they work helps us to design research studies, predict health impacts, and target prevention efforts.

The Occupational Cancer Research Centre has undertaken a variety of activities related to shiftwork to assess knowledge and needs within the stakeholder community and create a venue for ongoing discussion and research.

In April 2010, OCRC held a symposium on the health effects of shiftwork in conjunction with the Institute for Work and Health. This meeting brought together the research, employer, labour, and workers’ compensation communities to discuss and evaluate the state of scientific evidence on shiftwork and human health. Presentations from international experts focused on the prevalence of shiftwork, biological mechanisms that may explain how shiftwork affects health, the results of animal studies, and the impact of shiftwork on worker injury, heart disease, fertility and cancer. Presentation slides from the symposium are available.

The Occupational Cancer Research Centre held a Carcinogen Classification Workshop in February 2012 to outline the process that the International Agency for Research on Cancer (IARC) uses to evaluate carcinogenicity, using shiftwork as the example. This workshop provided a background on the evidence of the health effects of shiftwork, including animal studies and epidemiologic studies, and showed why shiftwork was classified as a ‘probable’ carcinogen.

Recognizing the need for information on interventions that reduce the potential risks of injury and disease among shiftworkers, on November 6, 2012, the Occupational Cancer Research Centre and the Institute for Work and Health held a Shiftwork Interventions Symposium. In order to plan for this symposium, the OCRC and the Institute for Work and Health determined stakeholder needs and current knowledge via a web-based survey about workplace practices to prevent injury and illness due to shiftwork. The survey assessed knowledge of risk associated with shiftwork, identified types of interventions that have been proposed and/or implemented, determined who are the key players involved in shiftwork-related interventions, and collected information on what is needed to protect the health of shiftworkers. Survey respondents included workers, unions, employers, researchers, and policy-makers, among others. The survey results are now available.

Altogether, these efforts helped us develop a comprehensive picture of current knowledge and workplace practices for the prevention of injury and disease related to shiftwork. We have raised awareness of both the health effects of shiftwork and practical interventions among the stakeholder community.

The impact of night shift work has also been investigated in the Burden of Occupational Cancer project.