Shift work is a widespread feature of our society, with a third of men and a fifth of women in the UK engaged in it. However, shift work has been linked with a number of poor health outcomes, including obesity, diabetes, heart disease, depression and some types of cancer. The pathways mechanisms by which shift work might lead to these diseases are poorly understood. A major area of interest is the effect shift work, and night shift work in particular, has on altering a person’s body clock. There is information available on shift work patterns at multiple time points in Understanding Society. The availability of blood samples for some study participants provides an opportunity to look at biological changes associated with shift work, including the impact shift work might have on epigenetic modifications, which influence how our genes are expressed turned on or off (via epigenetic changes). This work will help us better understand how the occupational exposure of working shifts might become embodied in human biology, with the potential for long term health consequences.