Professor David KennawayMore than 1.4 million Australians work outside normal working hours. Shift work and increased light exposure at night has been associated with poor sleep and fatigue, resulting in workplace accidents and incidents. But there is now emerging evidence that shift work is a significant public health issue, with the workers being at significantly higher risk of developing or exacerbating chronic diseases. Since 2009 there have been more than 50 workplace-based studies reporting increased risk of Metabolic Syndrome, in particular vascular events, diabetes/impaired glucose tolerance, elevated BMI/obesity, as well as adverse impacts on fertility/pregnancy and increased risk of breast, ovary and prostate cancers.We do not yet know why night-time activity and daytime sleep increase the risk of developing or exacerbating chronic diseases; but one strong possibility is that this lifestyle disrupts fundamental cellular circadian rhythms that are essential for normal physiological functions. In 2012 the American Medical Association adopted a policy statement on night-time lighting and human health. They concluded that among the diseases exacerbated by circadian disruption are: “obesity, diabetes, depression and mood disorders, and reproductive problems. ... Due to the nearly ubiquitous exposure to light at inappropriate times relative to endogenous circadian rhythms, [we need] further multidisciplinary research on occupational and environmental exposure to light-at-night, the risk of cancer and effects on various chronic diseases.”I have made major contributions to our understanding of circadian physiology and through unique and significant cutting-edge research, have revealed how disrupted circadian and cell rhythms affect major physiological systems. My group, for example, was the first to show that circadian rhythm disruption during pregnancy pre-disposes the offspring to metabolic disorders later in life.