Shiftwork: Health effects and interventions


Our goal is to raise awareness of night shiftwork as a probable cancer risk factor, and identify practical interventions that can be used in workplaces to reduce the negative health effects of shiftwork.

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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.

Health Effects Symposium

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.

Carcinogen Classification Workshop

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.

Interventions Symposium

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.

Workshop Materials
  • The Health Effects of Shiftwork Symposium

  • Carcinogen Classification Workshop

  • Shiftwork Interventions Symposium

Reports and Fact Sheets
  • OCRC Report: Workplace practices to address the health effects of shiftwork | Stakeholder knowledge and needs survey

  • Shiftwork, Breast Cancer and Health: Interventions to Reduce the Risks

  • Shift work in Canadian industries - a probable cancer risk factor

Scientific Articles
  • Health-related interventions among night shift workers: a critical review of the literature

  • Physical activity, physical fitness, and body composition of Canadian shift workers: data from the Canadian health measures survey cycles 1 and 2

  • Shiftwork trends and risk of work injury among Canadian workers

  • The impact of night shift work on breast cancer: Results from the Burden of Occupational Cancer in Canada Study

  • Night shift work and breast cancer risk: what do the meta-analyses tell us?

  • Use of a Canadian Population-Based Surveillance Cohort to Test Relationships Between Shift Work and Breast, Ovarian, and Prostate Cancer

Research Team
Cam Mustard
Institute for Work and Health
Kristan Aronson
Queen’s University
Paul Demers
Desre Kramer
Manisha Pahwa
Anne Harris
Ryerson University
Carolyn Gotay
Canadian Cancer Society-University of British Columbia Cancer Prevention Centre
Sarah Neil
University of British Columbia
Ron Saunders
Institute for Work and Health