Mid Sweden University

Shift work is often defined as working time outside daytime hours (06:00 to 18:00). In recent years, shift work has been associated with an increased risk of cardiovascular disease (CVD), type II diabetes, and the metabolic syndrome. While some studies support the associations, others do not. Therefore, more research is needed. The aim of this thesis was to further study the association between shift work and CVD. This was addressed by performing four studies, one analysed if shift workers had an increased risk of ischemic stroke, the second study analysed whether shift workers had an increased risk of short-term mortality (case fatality)after a myocardial infarction (MI). The third study analysed if shift work interacts with other risk factors for MI and the fourth study analysed if parental history of CVD interacted with shift work on the risk of MI. The studies were performed using logistic regression analyses and additive interaction analyses in two different case-control databases. Shift workers did not have an increased risk of ischemic stroke. Male shift workers had an increased risk of death within 28 days after a MI. Shift work interacts with some CVD risk factors and interacts with paternal history of CVD and the risk of MI for males. The findings from this thesis provide new evidence showing that shift work is in different ways associated with an increased risk of MI and related mortality, but not with ischemic stroke. However, more research is needed to clarify and characterise these results.