Principles of sleep-wake regulation

Given the expanding number of associations emerging between sleep behaviour and health, measurement of sleep will become increasingly important, if not obligatory, in population-based public health research. This chapter provides the epidemiologist with a basic understanding of the physiological principles underlying sleep-wake regulation and how they might be considered when measuring sleep in epidemiological studies. Sleep is an active, rhythmic process with periodicities on multiple time scales, including homeostatic, ultradian, and circadian cycles. Measurement of sleep first of all requires a definition of what sleep is and estimates of sleep behaviour can be captured using a range of different methods. The chapter highlights possible confounding factors that might be considered when interpreting sleep data, and discusses the potential for sleep to affect the accurate measurement of other biomarkers in health research.