Methods for Assessing Human Sleep

Over the last two decades there has been a great increase in interest and experimentation in the physiology and pathology of sleep. This has involved many different disciplines such as neurophysiology, general physiology, biochemistry, pharmacology, endocrinology, psychology, and psychiatry. The description of changes in the electroencephalogram during sleep by Loomis et al in 1935¹and the later definition of sleep stages by Dement and Kleitman in 1957²greatly facilitated these investigations. Similarly, the discovery of a relationship between rapid eye movements (REM), a low-amplitude fast-frequency EEG, and subjective reports of dreaming has been followed by many objective investigations into the nature of the dreaming state which previously had not been possible. The nature of sleep disturbances in psychiatric illness and the effects of hypnotic drugs, which are so widely used but so little understood, are now the subject of intense research. Normal sleep habits and the epidemiology of