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The importance of quality sleep is becoming increasingly recognized by the general population, yet sleep is still not commonly addressed as part of a comprehensive medical evaluation. Sleep disturbances can increase the risk of many medical disorders and worsen preexisting medical conditions such as epilepsy. Poor sleep can also affect social and emotional well-being and may result in symptoms misattributed and subsequently treated as attention disorders.

Behaviorally induced insufficient sleep syndrome has reached an epidemic proportion in many developed countries. Reaffirmation of the need to allocate 7–8 hours for sleep per 24-hour period is cited by groups such as the World Health Organization and National Sleep Foundation. The timing, duration, and intrinsic qualities of sleep, as well as extrinsic factors that may impede it need to be considered in the detailed evaluation of this physiologic state.


Sleep consists of four stages, each defined primarily by its electroencephalogram (EEG) characteristics analyzed in 30-second chunks, called epochs. These are N1, N2, N3, and R (Figure 31–1). N1 and N2 are considered “light sleep.” N3 is also called slow wave sleep, deep sleep, or delta sleep. In R sleep, there are autonomic fluctuations, breathing is irregular, and the body is paralyzed, although rapid eye movements (REMs) occur. Sleep in a normal young adult is typically 5% N1, 45% N2, 25% N3, and 25% R. During sleep, the brain cycles from N1, N2, N3, to R every few hours (the ultradian rhythm). However, most of the N3 sleep is obtained in the first third of the night, and most of the R sleep is obtained in the last third. Durations of N3 become progressively shorter while cycles of R become progressively longer. On recovery from a sleep-deprived state, an increase in N3 followed by an increase in R sleep is seen on one or subsequent nights.

Figure 31–1.

A hypnogram showing the cycling through various stages of sleep (R, 1, 2, and 3) through the night with successively deep sleep (3) and more rapid eye movement (REM) sleep (R) as the night progresses and few awakenings (W).


Sleep timing and duration can be assessed using sleep logs or diaries as well as by instrumentation such as actigraphy. An actigraph is a device typically worn on the wrist that measures movement in order to estimate sleep parameters. Personal health devices that track sleep are inaccurate and should not be solely relied on in a sleep evaluation. The home sleep apnea test (HSAT) evaluates specifically for breathing disturbances and may not evaluate sleep architecture. Consequently, results may underestimate severity of sleep-disordered breathing or produce false-negative results. The test is used for convenience and may be a required first-line investigation for individuals who have difficulty maintaining sleep or present with ...

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