ABSTRACT
The sleep-wake cycle is governed by neuronal processes that control alertness and the tendency to sleep. This cycle in humans is a balance between endogenous circadian and ultradian (more than one cycle per 24 hours) processes, but is inuenced by external factors such as light, temperature and social mores (zeitgebers) that entrain the individual to the environment. Broadly, the abnormalities of sleep that affect daytime function are sleep deprivation and sleep disruption. Clients will present as ‘too sleepy’ or having insufcient sleep. Both can result from a variety of social pressures or disorders that are either intrinsic to sleep or caused by other medical conditions. This chapter will consider the medical conditions that affect sleep and impact on daytime function, secular changes in sleep habits, primary problems with sleep that affect sickness absence and occupational aspects related to circadian issues-shift work and extended working hours.
