Sleep is core to our ability to function and there is increasing evidence that poor or mis-timed sleep increases our risk of cardio vascular disease, type II diabetes, obesity and cognitive decline. In this talk I will discuss the mechanisms that are believed to underlie sleep wake regulation and review some recent mathematical models. In particular, I will focus on age-related changes to sleep and explain how the mathematical models can be used to bring insight into the possible mechanisms that could cause these changes.