With normal physiologic sleep, a person feels adequately restored. The amount of sleep needed varies with the person but is generally about 7 hours a night, with a standard deviation of 1 hour. Many people are probably sleep-deprived (Barthlen & Stacey, 1994).

The stages of sleep follow a predictable pattern of rapid eye movement (REM) and nonrapid eye movement (NREM) sleep with corresponding physiologic functions. The neuroanatomy, neurophysiology, and biochemistry of sleep and wakefulness are not completely understood (Gillin et al, 1995).

Patients with primary insomnia may appear tired, exhausted, and weary; however, there may be no other characteristics on the physical exam. Polysomnography (PSG) may show alterations in sleep continuity and stages of sleep, increased muscle tension, and increased electroencephalographic (EEG) alpha activity.

Disorders that may cause insomnia include obstructive sleep apnea (OSA), periodic limb movement disorder (PLMD), and restless limb syndrome (RLS). PLMD and RLS are poorly understood disorders that interrupt sleep due to limb movements and sensations. They may be related to other medical conditions.

Obstructive sleep apnea (OSA) is caused by a collapse of the pharyngeal airway during sleep, despite continuous efforts to breathe. Airway muscles relax and the airway closes in a person with an anatomically small pharyngeal airway. Breathing resumes after a brief arousal or awakening. During apneic periods, there is a progressive blood oxygen desaturation and an increase in carbon dioxide. With each arousal, the person returns to a deeper stage of sleep, with subsequent periods of apnea and arousal. As the disease progresses, the duration of apneic periods and the degree of hypoxemia increase. Sequelae include:

Symptoms increase when the person drinks alcohol, takes a depressant drug, or changes sleep patterns. There may also be a reduction in intellectual capacity, personality changes, sudden bursts of anger and hostility, and impairments in social and work life (Jaquis, 1987; Stradling, 1995; White, 1995; Williams et al, 1995).

The pathophysiology of narcolepsy results in a disturbance of control of both REM and NREM sleep onset and offset. There is resulting disruption of nighttime sleep and the impingement of sleep into daytime wakefulness (Mahowald, 1996). Narcolepsy is considered a disorder of REM sleep mechanisms. There has not been supporting evidence thus far for the hypothesis that narcolepsy is an autoimmune disorder, based on the extremely high rate (up to 100%) of occurrence with HLA DR2 (Barthlen & Stacey, 1994).

Studies show a 1-year prevalence rate of insomnia complaints of 30% to 40% in adults (American Psychiatric Association [APA], 1994). The incidence of narcolepsy is estimated at 0.02% to 0.09% (Williams et al, 1995), with a prevalence of more than 50 per 100,000, and a genetic linkage. Narcolepsy occurs in 10% of first-degree relatives and excessive daytime sleepiness in up to 30% (Barthlen & Stacey, 1994).

OSA predominantly affects middle-aged, overweight men; however, it can occur at all ages and in both sexes (Williams et al, 1995). The prevalence is approximately 4% in men and 2% in women, with higher rates in African Americans, older people, obese people, and those with hypertension, hypothyroidism, and upper airway anatomic abnormalities (Young, 1993).

Restless leg syndrome (RLS) occurs in 5% to 10% of the population, with a strong family history. The rate of periodic limb movement disorder (PLMD) increases in patients older than age 60; it occurs rarely in patients younger than 30 and is found in nearly half of patients older than 65 (Barthlen & Stacey, 1994; Jamieson & Becker, 1992).

There is an increase in sleep disturbances in the elderly, with a greater number of awakenings, possibly as a result of the increased incidence of sleep-related breathing disorders (mild apnea) and PLMD. The elderly also sleep less efficiently and have more circadian rhythm changes (Moran & Stoudemire, 1992).

Many patients with insomnia can be successfully managed by a primary care provider. An in-depth interview to obtain a full description of the problem is the most important diagnostic
procedure. A sleep laboratory study (PSG) may also be indicated. Changes in sleep habits and patterns should alert the primary care provider to the possibility of a sleep disorder; however, not all disturbances in sleep are symptomatic of a primary sleep disorder. It is important to inquire about sleep as part of the routine assessments, because some patients will not describe problems otherwise. An accurate diagnosis can be difficult, because many different sleep disorders share signs and symptoms (Williams et al, 1995).

There is frequently a close connection and interaction between the quality of sleep and health problems (Moran & Stoudemire, 1992). The primary care provider should listen carefully for symptoms of depression, bipolar disease, anxiety disorder, panic disorder, substance abuse, or psychosis (Barthlen & Stacey, 1994). Disordered sleep is also found in dementia, parkinsonism, epilepsy, nocturnal cardiac ischemia, sleep-related gastroesophageal reflux, peptic ulcer disease, sleep-related asthma, and fibromyalgia (Barthlen & Stacey, 1994; Williams et al, 1995).

The APA’s Diagnostic and Statistical Manual of Mental Disorders, 4th edition (1994), classifies sleep disorders into four main classes:

Dyssomnias are basic disorders of initiating or maintaining sleep or of excessive sleepiness, characterized by a disturbance in the amount, quality, or timing of sleep. Parasomnias are disorders that include unusual behavior or physiologic events that occur in association with sleep.