Sleeping outside the lines: The effects of social jetlag on glycemic and metabolic control

This thesis focuses on the association between social jetlag, a chronic mismatch between social and biological sleep timing, and markers of glycemic and metabolic control. In part 1, we examined whether social jetlag is associated with glycemic and metabolic control in the general population and in people with type 2 diabetes. We found cross-sectional associations with BMI, waist circumference, blood pressure and glucose levels, but no consistent prospective associations. In part 2, we studied mechanistic pathways that could explain these associations. We found that lifestyle factors partly explain the association between social jetlag and BMI but we could not confirm other proposed pathways and these remain to be studied. Part 3 of this thesis describes a study protocol of a randomized controlled trial that aims to reduce social jetlag and assess the effects on glycemic and metabolic control. This study is ongoing and still needs to point out whether reducing social jetlag could improve health. More attention for sleep and sleep timing in addition to dietary and physical activity guidelines could help in the prevention of conditions such as the metabolic syndrome and type 2 diabetes. Also, more general awareness of the importance of our sleep timing and more flexible school start times and work schedules could help reduce social jetlag.