The Value of Sleep for Optimizing Health

We spend a third of our lives sleeping, a behavioral state that typically requires the person to lie recumbent in the dark with eyes closed, in a comfortable, quiet, and safe location. If evolutionary processes, spanning millions of years, are responsible for fine-tuning our adaptive advantage, then it stands to reason that sleep must be an evolved adaptation important for the survival (and health) of all mammalian species. Since the 1950s, when the different stages of sleep were first identified, enormous intellectual and physical resources have been dedicated to the task of identifying a function (or set of functions) for sleep and to better understand why sleep is so important for general health. Prominent among the many scientific hypotheses of sleep function are whether (and how) sleep serves a basic restorative function, a memory/cognition function, and/or a general health function. In contrast to these health-oriented hypotheses of sleep function is the reality that lost and disrupted sleep promote their own set of negative health outcomes. This chapter will describe what is known about healthy sleep, disrupted sleep, and sleep loss and their general effects on cognitive and physical health. An efficient, practical clinical assessment of sleep quality and quantity and the approach to sleep interventions are also described.