1 in 5 Australian workers operate outside the “normal” hours of 8am to 6pm, are forced to sleep during the day, often in noisy environments and have reduced sleep time and poor quality sleep. Some of the greatest environmental disasters, 3-Mile Island, Chernobyl and the Exxon Valdez wreck all happened during night shifts. Fatigue clearly is a major OHS issue for industries using shiftworkers. There is also a more personal side to the impact of shiftwork. In recent years evidence has emerged that shiftwork may be a hidden contributor to the development of some important chronic diseases. For example shiftworkers are at an increased risk of developing diabetes, cardiovascular disease and becoming obese, as well as developing certain cancers. And the longer you do shiftwork, the higher the risk of disease.

Humans are diurnal and our physiological systems have evolved accordingly. For example in the hypothalamus the suprachiasmatic nucleus (SCN) operates as a “clock” powered by a suite of clock genes and is entrained to the environment by light perception via the retina. This “central master clock” coordinates brain function (e.g. the timing of sleep) as well as clock gene expression and specific, rhythmic, “functional” genes in the liver, muscle, adipose, pancreas, etc. Importantly shiftworkers, like day-workers, are exposed to light during the day during their commute or in their bedrooms. As a consequence, they rarely re-adjust their central SCN rhythmicity to their nocturnal work schedules and continue to secrete melatonin at night while working. Emerging evidence implicates the conflict between central and peripheral clocks as a contributor to pathological changes in organ function, such as insulin resistance.

Shiftwork is not going away and is in fact expected to increase in Australia with the mining boom. There is an urgent need to understand what is happening to the health of shiftworkers and to develop strategies to minimise the risk that they are exposed to, either by designing better rosters, better lighting systems, identifying those at particularly high risk of developing chronic disease or by developing drugs to reset the cellular timing system.