Scientific Symposium on the Health Effects of Shift Work

On April 12, 2010, the Canadian Occupational Cancer Research Centre and the
Institute for Work & Health (IWH) co-hosted a scientific symposium on the
health effects of shift work. More than 100 researchers and representatives
from the employer, labour and workers’ compensation communities - primarily
from Ontario, but also other parts of Canada, the United States and Europe -
came together in Toronto to participate in the symposium. The aim was to
provide an overview from leading scientific experts on research findings about
the health effects of shift work, and collectively identify the key gaps in the
research evidence. The results now available online.

Key findings presented at the symposium are:

  • Shift work is common. About one-quarter of the workforce in North America and Europe is engaged in shift work requiring working at night. In Canada, 11 per cent of workers work rotating shifts, six per cent work regular evening shifts and two per cent work regular night shifts.

  • Shift work can result in sleep disruption and sleep deprivation, and in sleepiness/fatigue at work.

  • Night shift work has been associated with an increase in breast cancer in women who work rotating shifts for longer durations (i.e. 30-plus years).

  • A number of biological mechanisms to explain the association between light at night and cancer risk are being explored. The key ones are the suppression of the normal night-time production of melatonin and the disruption of the circadian gene function.

  • Evidence from animal studies supports the link between circadian disruption (in the form of suppressed melatonin production) and the growth of tumours.

  • In 2007, based on limited evidence from human studies and sufficient evidence from animal experiments, the International Agency for Research on Cancer (IARC) classified "shift work that involves circadian disruption" (i.e. night shift work) as a probable human carcinogen.

  • There is strong evidence that night, evening, rotating and irregular shifts are associated with an elevated risk of workplace injuries.

  • There is not enough high quality evidence to reach firm conclusions on the influence of shift work on heart disease.

  • There is evidence that shift work has a moderate negative effect on fetal growth in pregnant women.

More information - Source: European Agency for Safety and Health at Work