Every day over six billion people and innumerable animals on earth succumb to the need for sleep. However, many fundamental questions such as ‘What is sleep?’ ‘How is it controlled?’ ‘How can we measure it?’ ‘Why do we need it?’ ‘How much is required?’ and ‘What happens if you do not get enough?’ are still to be fully answered. This article will briefly examine these and some related questions. It will examine some of the factors that are known to regulate sleep, how it is measured and how much is considered ‘normal’. It will discuss the consequence to an individual or society of insufficient or poor quality sleep. In turn, it will consider whether individuals who ‘sleep for excessive periods’ of time, who are ‘slow at doing things’ or who appear to be ‘lazy’ are willingly complicit to committing the deadly sin ‘sloth’ or whether their ‘abnormal’ sleeping patterns or observed ‘excessive daytime sleepiness’ (EDS) may be ‘normal’ for their age, caused by different sleep needs, the result of underlying sleep disorders and/or other health problems.

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