The dark side of night shift

When the NSW Industrial Relations Commission last looked at shift penalty rates in 1972 scientific research into the health impacts of shift work was embryonic and the health effects were believed to be minor.

Thirty-six years later there has been an explosion in the amount of sleep and circadian research. The completion of the mapping of the human genome in 2006 further enabled the understanding of the genes that regulate human circadian rhythms (biological clocks).

The evidence submitted in the NSWNA case to the NSW IRC by Professor Ron Grunstein from the Woolcock Institute of Medical Research, shows the poor health effects of night shift.

‘There’s compelling evidence that a range of poor health indicators are found in individuals exposed to rotating shift work involving night work,’ reported Professor Grunstein.

‘A strong body of research has demonstrated that the longer an individual performs shift work, especially shift work that comprises a night duty rotation, the greater the risk of serious illness for that shift worker.’

Some of the evidence comes from very large research projects on nurses in the United States including one that investigated the health risk factors of 121,700 female, married nurses, aged 30 to 55 years over a period of 30 years.

The studies show that shift workers have increased risks of breast cancer, cardio-vascular disease, gastro-intestinal disorders and reproductive health problems.

Professor Grunstein said the evidence is so compelling that in November 2007 the working group of the World Health Organisation International Agency for Research on Cancer ranked ‘shiftwork that involves circadian disruption’ on the second highest of five tiers used to grade exposure and carcinogenicity to humans’.

He also said there is ample and consistent evidence to conclude that night or rotating shiftwork poses a serious health risk for the worker. This evidence did not exist when the night penalty rates were last reviewed in 1972.

‘The risks are serious, not transitory or minor, with evidence of increase with repeated exposure,’ he said.