Abstract
Since the discovery of electroencephalography to measure brain activity in 1924, sleep research has rapidly advanced. Contemporary sleep research no longer focuses on the length of sleep and the consequences of sleep loss. Instead, a multitude of sleep parameters, such as sleep duration, quality, irregularity, health, and disordered sleep, now inform the sleep science community about the importance of sleep in relation to health, performance, cognitive, cultural, and clinical outcomes through diverse study designs, equipment, and across a range of populations. This special issue on sleep and its disorders has shown us how diverse and widespread the study of sleep has become today. Geographically, it is remarkable that we received manuscripts from various continents and from dozens of countries. The themes and approaches were equally diverse, ranging from population-based studies to laboratory investigations, and including discussions of public policies related to sleep.