People experience cyclical rhythms as part of their everyday lives. The most familiar rhythm is the 24-hour, day-night cycle known as the diurnal or circadian rhythm (derived from Latin: circa, “about,” and dies, “day”). The suprachiasmatic nucleus (SCN) nerve cells in the hypothalamus control the rhythm of the sleep-wake cycle and coordinate this cycle with other circadian rhythms (McCance et al., 2010). Circadian rhythms influence the pattern of major biological and behavioral functions. The predictable changing of body temperature, heart rate, blood pressure, hormone secretion, sensory acuity, and mood depend on the maintenance of the 24-hour circadian cycle (Van der Zee et al., 2009).

Factors such as light, temperature, social activities, and work routines affect circadian rhythms and daily sleep-wake cycles. All persons have biological clocks that synchronize their sleep cycles. This explains why some people fall asleep at 8 PM, whereas others go to bed at midnight or early in the morning. Different people also function best at different times of the day.

Hospitals or extended care facilities usually do not adapt care to an individual’s sleep-wake cycle preferences. Typical hospital routines interrupt sleep or prevent patients from falling asleep at their usual time. Poor quality of sleep results when a person’s sleep-wake cycle changes. Reversals in the sleep-wake cycle, such as when a person who is normally awake during the day falls asleep during the day, often indicate a serious illness.

The biological rhythm of sleep frequently becomes synchronized with other body functions. For example, changes in body temperature correlate with sleep patterns. Normally body temperature peaks in the afternoon, decreases gradually, and then drops sharply after a person falls asleep. When the sleep-wake cycle becomes disrupted (e.g., by working rotating shifts), other physiological functions usually change as well. For example, a new nurse who starts working the night shift experiences a decreased appetite and loses weight. Anxiety, restlessness, irritability, and impaired judgment are other common symptoms of sleep cycle disturbances. Failure to maintain an individual’s usual sleep-wake cycle negatively influences the patient’s overall health.

Sleep involves a sequence of physiological states maintained by highly integrated central nervous system (CNS) activity. It is associated with changes in the peripheral nervous, endocrine, cardiovascular, respiratory, and muscular systems (McCance et al., 2010). Specific physiological responses and patterns of brain activity identify each sequence. Instruments such as the electroencephalogram (EEG), which measures electrical activity in the cerebral cortex; the electromyogram (EMG), which measures muscle tone; and the electrooculogram (EOG), which measures eye movements provide information about some structural physiological aspects of sleep.

The major sleep center in the body is the hypothalamus. It secretes hypocreatins (orexins) that promote wakefulness and rapid eye movement sleep. Prostaglandin D₂, L-tryptophan, and growth factors control sleep (McCance et al., 2010).

Researchers believe that the ascending reticular activating system (RAS) located in the upper brainstem contains special cells that maintain alertness and wakefulness. The RAS receives visual, auditory, pain, and tactile sensory stimuli. Activity from the cerebral cortex (e.g., emotions or thought processes) also stimulates the RAS. Arousal, wakefulness, and maintenance of consciousness result from neurons in the RAS releasing catecholamines such as norepinephrine (Izac, 2006).

Researchers hypothesize that the release of serotonin from specialized cells in the raphe nuclei sleep system of the pons and medulla produces sleep. This area of the brain is also called the bulbar synchronizing region (BSR). Whether a person remains awake or falls asleep depends on a balance of impulses received from higher centers (e.g., thoughts), peripheral sensory receptors (e.g., sound or light stimuli), and the limbic system (emotions) (Fig. 42-1). As people try to fall asleep, they close their eyes and assume relaxed positions. Stimuli to the RAS decline. If the room is dark and quiet, activation of the RAS further declines. At some point the BSR takes over, causing sleep.

Current theory suggests that sleep is an active multiphase process. Different brain-wave, muscle, and eye activity is associated with different stages of sleep (Izac, 2006). Normal sleep involves two phases: nonrapid eye movement (NREM) sleep and rapid eye movement (REM) sleep (Box 42-1). During NREM a sleeper progresses through four stages during a typical 90-minute sleep cycle. The quality of sleep from stage 1 through stage 4 becomes increasingly deep. Lighter sleep is characteristic of stages 1 and 2, during which a person is more easily aroused. Stages 3 and 4 involve a deeper sleep, called slow-wave sleep. REM sleep is the phase at the end of each sleep cycle. Different factors promote or interfere with various stages of the sleep cycle.

Once asleep, the person usually passes through four or five complete sleep cycles per night, each consisting of four stages of NREM sleep and a period of REM sleep (McCance et al., 2010). Each cycle lasts approximately 90 to 100 minutes. The cyclical pattern usually progresses from stage 1 through stage 4 of NREM, followed by a reversal from stages 4 to 3 to 2, ending with a period of REM sleep (Fig. 42-2). A person usually reaches REM sleep about 90 minutes into the sleep cycle. Seventy-five to eighty percent of sleep time is spent in NREM sleep.

With each successive cycle stages 3 and 4 shorten, and the period of REM lengthens. REM sleep lasts up to 60 minutes during the last sleep cycle. Not all people progress consistently through the stages of sleep. For example, a sleeper moves back and forth for short intervals between NREM stages 2, 3, and 4 before entering REM stage. The amount of time spent in each stage varies over the life span. Newborns and children spend more time in deep sleep. Sleep becomes more fragmented with aging, and a person spends more time in lighter stages (National Sleep Foundation, 2009). Shifts from stage to stage of sleep tend to accompany body movements. Shifts to light sleep or wakefulness tend to occur suddenly, whereas shifts to deep sleep tend to be gradual (Izac, 2006). The number of sleep cycles depends on the total amount of time that the person spends sleeping.

Although dreams occur during both NREM and REM sleep, the dreams of REM sleep are more vivid and elaborate; and some believe that they are functionally important to learning, memory processing, and adaptation to stress (Kryger et al., 2011). REM dreams progress in content throughout the night from dreams about current events to emotional dreams of childhood or the past. Personality influences the quality of dreams (e.g., a creative person has elaborate and complex dreams, whereas a depressed person dreams of helplessness).

Most people dream about immediate concerns such as an argument with a spouse or worries over work. Sometimes a person is unaware of fears represented in bizarre dreams. Clinical psychologists try to analyze the symbolic nature of dreams as part of a patient’s psychotherapy. The ability to describe a dream and interpret its significance sometimes helps resolve personal concerns or fears.

Another theory suggests that dreams erase certain fantasies or nonsensical memories. Because most people forget their dreams, few have dream recall or do not believe they dream at all. To remember a dream, a person has to consciously think about it on awakening. People who recall dreams vividly usually awake just after a period of REM sleep.

Insomnia is a symptom that patients experience when they have chronic difficulty falling asleep, frequent awakenings from sleep, and/or a short sleep or nonrestorative sleep (Kryger et al., 2011). It is the most common sleep-related complaint. People with insomnia experience excessive daytime sleepiness and insufficient sleep quantity and quality. However, frequently a patient gets more sleep than he or she realizes. Insomnia often signals an underlying physical or psychological disorder. It occurs more frequently in and is the most common sleep problem for women.

People experience transient insomnia as a result of situational stresses such as family, work, or school problems; jet lag; illness; or loss of a loved one. Insomnia sometimes recurs, but between episodes a patient is able to sleep well. However, a temporary case of insomnia caused by a stressful situation can lead to chronic difficulty in getting enough sleep, perhaps because of the worry and anxiety that develop about getting it.

Insomnia is often associated with poor sleep hygiene, or practices that a patient associates with sleep. If the condition continues, the fear of not being able to sleep is enough to cause wakefulness. During the day people with chronic insomnia feel sleepy, fatigued, depressed, and anxious. Treatment is symptomatic, including improved sleep hygiene measures, biofeedback, cognitive techniques, and relaxation techniques. Behavioral and cognitive therapies have few adverse effects and show evidence of sustained improvement in sleep over time (Babson et al., 2010).

Sleep apnea is a disorder characterized by the lack of airflow through the nose and mouth for periods of 10 seconds or longer during sleep. There are three types of sleep apnea: central, obstructive, and mixed apnea. The most common form is obstructive sleep apnea (OSA). Research estimates that 2% to 4% of the adults in the United States meet the diagnostic criteria for OSA (Adult Obstructive Sleep Apnea Task Force, 2009). The two major risk factors for OSA are obesity and hypertension (Sheldon et al., 2009). Smoking, heart failure, type II diabetes, alcohol, and a positive family history of OSA also greatly increase the risk of developing the problem (Adult Obstructive Sleep Apnea Task Force, 2009). It occurs in up to 2% of middle-age women and up to 4% of middle-age men, with occurrence higher in the older-adult population and African Americans (Malhotra and Desai, 2010).

OSA occurs when muscles or structures of the oral cavity or throat relax during sleep. The upper airway becomes partially or completely blocked, diminishing nasal airflow (hypopnea) or stopping it (apnea) for as long as 30 seconds (Kryger et al., 2011). The person still attempts to breathe because chest and abdominal movement continue, which often results in loud snoring and snorting sounds. When breathing is partially or completely diminished, each successive diaphragmatic movement becomes stronger until the obstruction is relieved. Structural abnormalities such as a deviated septum, nasal polyps, certain jaw configurations, larger neck circumference, or enlarged tonsils predispose a patient to OSA (Pinto and Caple, 2010). The effort to breathe during sleep results in arousals from deep sleep often to the stage 2 cycle. In severe cases hundreds of hypopnea/apnea episodes occur every hour, resulting in severe interference with deep sleep.

Excessive daytime sleepiness (EDS) and fatigue are the most common complaints of people with OSA. Persons with severe OSA often report taking daytime naps and experience a disruption in their daily activities because of sleepiness (Adult Obstructive Sleep Apnea Task Force, 2009). Feelings of sleepiness are usually most intense on awakening, right before going to sleep, and about 12 hours after the midsleep period. EDS often results in impaired waking function, poor work or school performance, accidents while driving or using equipment, and behavioral or emotional problems.

Obstructive apnea causes a serious decline in arterial oxygen saturation level. Patients are at risk for cardiac dysrhythmias, right heart failure, pulmonary hypertension, angina attacks, stroke, and hypertension. Sleep apnea contributes to high blood pressure and increased risk for heart attack and stroke (National Sleep Foundation, 2010b).

Central sleep apnea (CSA) involves dysfunction in the respiratory control center of the brain. The impulse to breathe fails temporarily, and nasal airflow and chest wall movement cease. The oxygen saturation of the blood falls. The condition is common in patients with brainstem injury, muscular dystrophy, and encephalitis. Less than 10% of sleep apnea is predominantly central in origin. People with CSA tend to awaken during sleep and therefore complain of insomnia and EDS. Mild and intermittent snoring is also present.

Patients with sleep apnea rarely achieve deep sleep. In addition to complaints of EDS, sleep attacks, fatigue, morning headaches, irritability, depression, difficulty concentrating, and decreased sex drive are common (Kryger et al., 2011). OSA affects quality of life issues such as marital relationships and interactions within and outside the family and often is an embarrassment to a patient (Adult Obstructive Sleep Apnea Task Force, 2009). Treatment includes therapy for underlying cardiac or respiratory complications and emotional problems that occur as a result of the symptoms of this disorder.

Narcolepsy is a dysfunction of mechanisms that regulate sleep and wake states. Excessive daytime sleepiness is the most common complaint associated with this disorder. During the day a person suddenly feels an overwhelming wave of sleepiness and falls asleep; REM sleep occurs within 15 minutes of falling asleep. Cataplexy, or sudden muscle weakness during intense emotions such as anger, sadness, or laughter, occurs at any time during the day. If the cataplectic attack is severe, a patient loses voluntary muscle control and falls to the floor. A person with narcolepsy often has vivid dreams that occur as he or she is falling asleep. These dreams are difficult to distinguish from reality. Sleep paralysis, or the feeling of being unable to move or talk just before waking or falling asleep, is another symptom. Some studies show a genetic link for narcolepsy (Ahmed and Thorpy, 2010).

A person with narcolepsy falls asleep uncontrollably at inappropriate times. When individuals do not understand this disorder, a sleep attack is easily mistaken for laziness, lack of interest in activities, or drunkenness. Typically the symptoms first begin to appear in adolescence and are often confused with the EDS that commonly occurs in teens. Narcoleptic patients are treated with stimulants or wakefulness-promoting agents such as sodium oxybate, modafinil (Provigil) or armodafinil (Nuvigil) that only partially increase wakefulness and reduce sleep attacks. Patients also receive antidepressant medications that suppress cataplexy and the other REM-related symptoms. Brief daytime naps no longer than 20 minutes help reduce subjective feelings of sleepiness. Other management methods that help are following a regular exercise program, practicing good sleep habits, avoiding shifts in sleep, strategically timed daytime naps if possible, eating light meals high in protein, practicing deep breathing, chewing gum, and taking vitamins (Kryger et al., 2011). Patients with narcolepsy need to avoid factors that increase drowsiness (e.g., alcohol; heavy meals; exhausting activities; long-distance driving; and long periods of sitting in hot, stuffy rooms).

Sleep deprivation is a problem many patients experience as a result of dyssomnia. Causes include symptoms (e.g., fever, difficulty breathing, or pain) caused by illnesses, emotional stress, medications, environmental disturbances (e.g., frequent nursing care), and variability in the timing of sleep because of shift work. Physicians and nurses are particularly prone to sleep deprivation as a result of long work schedules and rotating shifts. Chronic sleep deprivation is associated with development of cardiovascular disease, weight gain, type II diabetes, poor memory, depression, and digestive problems (Ohlmann and O’Sullivan, 2009).

Hospitalization, especially in intensive care units (ICUs), makes patients particularly vulnerable to the extrinsic and circadian sleep disorders that cause the “ICU syndrome of sleep deprivation” (Fontana and Pittiglio, 2010). Constant environmental stimuli within the ICU such as strange noises from equipment, the frequent monitoring and care given by nurses, and ever-present lights confuse patients. Repeated environmental stimuli and the patient’s poor physical status lead to sleep deprivation (Fontana and Pittiglio, 2010).

A person’s response to sleep deprivation is highly variable. Patients experience a variety of physiological and psychological symptoms (Box 42-3). The severity of symptoms is often related to the duration of sleep deprivation.

The parasomnias are sleep problems that are more common in children than adults. Some have hypothesized that sudden infant death syndrome (SIDS) is thought to be related to apnea, hypoxia, and cardiac arrhythmias caused by abnormalities in the autonomic nervous system that are manifested during sleep (Kryger et al., 2011). Because of an association between the prone position and the occurrence of SIDS, the American Academy of Pediatrics recommends that parents place apparently healthy infants in the supine position during sleep (Koren et al., 2010).

Parasomnias that occur among older children include somnambulism (sleepwalking), night terrors, nightmares, nocturnal enuresis (bed-wetting), body rocking, and bruxism (teeth grinding). When adults have these problems, it often indicates more serious disorders. Specific treatment varies. However, in all cases it is important to support patients and maintain their safety.

By the age of 2 children usually sleep through the night and take daily naps. Total sleep averages 12 hours a day. After 3 years of age children often give up daytime naps (Hockenberry and Wilson, 2011). It is common for toddlers to awaken during the night. The percentage of REM sleep continues to fall. During this period toddlers may be unwilling to go to bed at night because they need autonomy or fear separation from their parents.

On average a preschooler sleeps about 12 hours a night (about 20% is REM). By the age of 5 he or she rarely takes daytime naps except in cultures in which a siesta is the custom (Hockenberry and Wilson, 2011). The preschooler usually has difficulty relaxing or quieting down after long, active days and has bedtime fears, awakens during the night, or has nightmares. Partial awakening followed by normal return to sleep is frequent (Hockenberry and Wilson, 2011). In the awake period the child exhibits brief crying, walking around, unintelligible speech, sleepwalking, or bed-wetting.

The amount of sleep needed varies during the school years. A 6-year-old averages 11 to 12 hours of sleep nightly, whereas an 11-year-old sleeps about 9 to 10 hours (Hockenberry and Wilson, 2011). The 6- or 7-year-old usually goes to bed with some encouragement or by doing quiet activities. The older child often resists sleeping because he or she is unaware of fatigue or has a need to be independent.

On average teenagers get about hours of sleep per night. The typical adolescent is subject to a number of changes such as school demands, after-school social activities, and part-time jobs, which reduce the time spent sleeping (Noland et al., 2009). Shortened sleep time often results in EDS, which frequently leads to reduced performance in school, vulnerability to accidents, behavior and mood problems, and increased use of alcohol (Noland et al., 2009; Vallido et al., 2009).

Most young adults average 6 to hours of sleep a night. Approximately 20% of sleep time is REM sleep, which remains consistent throughout life. It is common for the stresses of jobs, family relationships, and social activities to frequently lead to insomnia and the use of sleep medication. Daytime sleepiness contributes to an increased number of accidents, decreased productivity, and interpersonal problems in this age-group. Pregnancy increases the need for sleep and rest. Insomnia, periodic limb movements, RLS, and sleep-disordered breathing are common problems during the third trimester of pregnancy (Kryger et al., 2011).

Complaints of sleeping difficulties increase with age. More than 50% of older adults report sleep problems (Neikrug and Ancoli-Israel, 2010). Older adults experience weakening, desynchronized circadian rhythms that alter the sleep-wake cycle (Neikrug and Ancoli-Israel, 2010). Episodes of REM sleep tend to shorten. There is a progressive decrease in stages 3 and 4 NREM sleep; some older adults have almost no stage 4, or deep sleep. An older adult awakens more often during the night, and it takes more time for him or her to fall asleep. The tendency to nap seems to increase progressively with age because of the frequent awakenings experienced at night.

The presence of chronic illness often results in sleep disturbances for the older adult. For example, an older adult with arthritis frequently has difficulty sleeping because of painful joints. Changes in sleep pattern are often caused by changes in the CNS that affect the regulation of sleep. Sensory impairment reduces an older person’s sensitivity to time cues that maintain circadian rhythms.

Sleepiness, insomnia, and fatigue often result as a direct effect of commonly prescribed medications (Box 42-4). These medications alter sleep and weaken daytime alertness, which is problematic (Kryger et al., 2011). Medications prescribed for sleep often cause more problems than benefits. Older adults take a variety of drugs to control or treat chronic illness, and the combined effects of their drugs often seriously disrupt sleep. Some substances such as L-tryptophan, a natural protein found in foods such as milk, cheese, and meats, promote sleep.

In the past century the amount of sleep obtained nightly by U.S. citizens has decreased to about 6.7 hours per night, causing many Americans to be sleep deprived and experience excessive sleepiness during the day (Ohlmann and O’Sullivan, 2009). Sleepiness becomes pathological when it occurs at times when individuals need or want to be awake. People who experience temporary sleep deprivation as a result of an active social evening or lengthened work schedule usually feel sleepy the next day. However, they are able to overcome these feelings even though they have difficulty performing tasks and remaining attentive. Chronic lack of sleep is much more serious and causes serious alterations in the ability to perform daily functions. Sleepiness tends to be most difficult to overcome during sedentary (inactive) tasks such as driving. There is an increased risk of motor vehicle accidents if an individual drives after less than 7 hours of sleep (Heaton et al., 2009).

In hospitals and other inpatient facilities noise creates a problem for patients. Noise in hospitals is usually new or strange and often loud. Thus patients wake easily. This problem is greatest the first night of hospitalization, when patients often experience increased total wake time, increased awakenings, and decreased REM sleep and total sleep time. People-induced noises (e.g., nursing activities) are sources of increased sound levels. ICUs are sources of high noise levels because of staff, monitor alarms, and equipment. Close proximity of patients, noise from confused and ill patients, ringing alarm systems and telephones, and disturbances caused by emergencies make the environment unpleasant. Noise causes increased agitation; delayed healing; impaired immune function; and increased blood pressure, heart rate, and stress (Dennis et al., 2010).

Light levels affect the ability to fall asleep. Some patients prefer a dark room, whereas others such as children or older adults prefer keeping a soft light on during sleep. Patients also have trouble sleeping because of the room temperature. A room that is too warm or too cold often causes a patient to become restless.

Weight loss or gain influences sleep patterns. Weight gain contributes to OSA because of increased size of the soft tissue structures in the upper airway (Kryger et al., 2011). Weight loss causes insomnia and decreased amounts of sleep (Benca and Schneck, 2005). Certain sleep disorders are the result of the semi-starvation diets popular in a weight-conscious society.