Insomnia

Robert N. Turner

Difficulties with initiating and/or maintaining sleep have been described for centuries, yet significant progress in the understanding of these problems has occurred only within the past 60 years or so. Some cultures believed that disturbed sleep and dreams were associated with evil spirits and ghosts. Others have suggested that the gods determined poor sleep and the severity of the condition was in proportion to one’s sinful deeds. As significant mysticism surrounded the complaint of sleep disturbances, remedies for these troubles included religious practices as well as assorted other rituals and various compounds. Disturbed sleep has long been associated with a wide variety of medical and psychological conditions. Chronic and acute pain, allergies, and various other disease processes have certainly disturbed the sleep of many throughout the centuries. In addition, psychiatric conditions and insomnia have long been described. An early study with groups of good and poor sleepers suggested a biologic basis for insomnia, with greater physiologic arousal, including higher electromyogram levels and a faster heart rate, among poor sleepers (1). These differences were noted both during wakefulness and during sleep.

ISSUES OF DEFINITION

What Is Insomnia?

From our own lifetime experiences, most of us intuitively understand what is meant by the term “insomnia.” There are criteria for diagnosis provided by the American Academy of Sleep Medicine (AASM). Short-term insomnia is considered a transient disturbance, typically lasting a few days to a few weeks, and typically not requiring treatment. Chronic insomnia persists for months or even years. The International Classification of Sleep Disorders, 3rd edition (ICSD-3) (2) requires that adults and children diagnosed with insomnia report one or more of the following:

Difficulty initiating sleep
Difficulty maintaining sleep
Waking up earlier than desired
Resistance to going to bed on an appropriate schedule
Difficulty sleeping without parent or caregiver intervention

In the past, subtypes of insomnia were described, but patients often failed to fit into a single category. Multiple sleep symptoms are more common than any single symptom, with symptoms occurring simultaneously or switching from one to another over time. In addition, patients with insomnia often overestimate the time taken to fall asleep and underestimate sleep duration, indicating an altered perception of sleep (3).

Patients with insomnia vary in the amount of sleep per night. Some people may feel alert, refreshed, and energized with only 6 hours of sleep, whereas other individuals may feel “horrible” after such a “poor” night’s sleep. In addition, some regularly require more than an hour to initiate sleep, awaken four or more times during the sleep episode, and generally sleep about 6 hours per night, yet do not complain of insomnia. Others may awaken early in the morning. They may not complain of poor sleep. However, some may experience sleep-onset problems when requiring longer than 15 minutes to fall asleep, complain of insomnia with one or two brief awakenings during the sleep episode, and/or describe disturbed sleep if awakened earlier than usual. How do we make clinical sense of this?

First, the subjective experience of insomnia may have little to do with currently utilized objective sleep-electroencephalogram (EEG) parameters. Considerable variability obviously exists between one’s perception and impression of sleep and laboratory findings (sleep latency and sleep duration). There exists a possibility that several other important measures of physiologic functioning, both during wakefulness and during sleep, which are not routinely employed in clinical evaluation settings, may more accurately reflect the subjectively experienced complaint of insomnia. As such, our current view of insomnia remains limited and only a partial view of the entire problem is understood.

Second, people with other sleep-wake disorders may incorrectly perceive that their problem is insomnia. Consider the middle-aged, moderately overweight, “stressed-out” male who snores and awakens frequently. He may believe that his problem is insomnia, yet obstructive apnea is one of his significant problems. Another example is a 50-year-old married female with a history of recurrent depression, migraine headaches, fibromyalgia, and asthma. Upon polysomnographic evaluation, snoring with repetitive arousals and stereotypic movements of the lower extremities are observed. Diagnoses may include upper airway resistance syndrome, periodic limb movement sleep disorder, and major depressive disorder. Both patients complain of insomnia, yet objective evaluation reveals other causes, likely promoting the experience of inadequate, nonrefreshing sleep.

Third, people may have disorders comorbid with insomnia. In other words, the patients described previously may have obstructive apnea and insomnia, or perhaps most commonly, depression and insomnia. In the past, primary insomnia was intended to represent discrete conditions, predicated upon conditioning factors, sleep-wake processes, and other matters as well. Secondary insomnia referred to the disturbance as a symptom associated with other variables, such as personality styles, numerous illnesses and disease, and a variety of psychiatric disorders. However, the cause-and-effect relationships of these factors have been difficult to determine. The most recent version of the ICSD (2) uses the term “comorbid” instead of secondary, reflecting a complex interaction between insomnia and other disorders. This is evident in a variety of medical disorders, especially those associated with pain; many psychiatric disorders, especially depression; and in interactions between sleep and medications used to treat comorbid disorders.

Fourth, circadian and aging factors also require consideration. In general, variations in core body temperature are correlated with the timing and duration of sleep and alertness. Older people may exhibit a lower amplitude of temperature rhythms and may also advance the sleep-alertness phase to an earlier time than younger people. Older patients may also report more frequent awakenings during the major sleep episode and complain of sleep-maintenance insomnia, whereas younger patients may describe sleep-onset insomnia. Both circadian and aging issues require consideration of normal sleep and rhythmic processes across the life span.

Fifth, in order to meet ICSD-3 criteria for diagnosis (2), some degree of distress must be associated with the complaint. It has long been known that poor sleep can be associated with decrements in mood and performance. Consequences of poor sleep can be described in terms of interpersonal, emotional, cognitive, vocational, and/or other areas of general functioning. Resultant sleepiness during normal waking hours may or may not occur. Although these troubles can be merely annoying with short-term insomnia, data suggest the potential medical consequences of persistent difficulties initiating and/or maintaining sleep.

Sixth, chronic insomnia may be conceptualized as a disorder of hyperarousal. It is essential that one is aware of the potential 24-hour overactivation of the hypothalamic-pituitary-adrenal (HPA) axis and/or other systemic physiologic processes, because these may be primary etiologic factors. As mentioned, hyperarousal is typically present throughout the day and night (1).

To summarize, numerous factors, characteristics, and consequences are associated with insomnia. These sleep-wake disturbances require careful consideration of many potential medical/psychiatric factors in the complaint of insomnia, as well as environmental factors, primary sleep-wake pathologies, and numerous other variables.

EPIDEMIOLOGY

Early epidemiologic studies indicated that approximately one-third of respondents to surveys described sleep difficulties over the previous year and at least 50% reported the experience of insomnia at some time during their lives. Severe or constant sleep troubles were reported by about 10% to 30% and an estimated 6% meet criteria for the diagnosis of insomnia (4). The most frequent type of disturbance was sleep-maintenance insomnia, whereas sleep-onset insomnia and early-morning awakening insomnia were less common. Importantly, some individuals reported a combination of these troubles.

More recent studies have documented daytime consequences of insomnia. Patients with insomnia reported memory problems and attention/concentration impairments, as well as mood decrements and less positive experiences with interpersonal relationships. Katz and McHorney (5) found that insomnia was associated with a worsened quality of life among a variety of patients with various illnesses. Collectively, evidence indicates that insomnia is widely prevalent, associated with daytime consequences, correlated with medical and mental health conditions, and associated with a reduced quality of life.

SHORT-TERM INSOMNIA

Short-term insomnia, or a brief episode of trouble falling and/or remaining asleep, affects almost everyone from time to time. Short-term insomnia is defined as a sleep problem lasting less than 3 months. During periods of stress or change (such as the loss of a loved one), individuals may exhibit time-limited difficulties with sleep. Sparingly studied through empirical methods, much remains unknown about this common problem within the general population.

According to the ICSD-3 (2), the diagnosis of short-term insomnia requires that a sleep disturbance occurs for less than 3 months and represents a clear change from the person’s typical sleep-wake patterns and habits.

Numerous external factors may promote short-term insomnia. Environmental disturbances, such as light and noise, stress, problematic interpersonal circumstances, and other matters, can initiate the problem. Changing one’s typical circadian sleep-wake pattern and drug initiation and/or withdrawal are also possible contributors to short-term insomnia. Other external events, internal circumstances (e.g., medical problems), and short-duration pain or discomfort can also promote short-term insomnia. It is important to keep in mind that this time-limited, usually resolvable, problem can become a very significant issue in people’s lives. It is well known that numerous factors can activate short-term insomnia. Personality style, genetic makeup, vulnerability to psychiatric illness, medical problems, and other issues can make the patient susceptible to persistent insomnia.

CHRONIC INSOMNIA

Criteria for the diagnosis of chronic insomnia are provided in ICSD-3 (2). These problems must occur for 3 months or longer, and some degree of daytime impairment or distress is essential. The new classification system makes the diagnosis a binary decision—yes or no. Previous insomnia subcategories may have some value in tailoring treatment plans to address primary complaints, but no longer have an influence on whether or not the diagnosis is made.

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