Insomnia
Approximately 40% of the general population experiences intermittent or chronic insomnia at least once. Epidemiologic studies find that between 10% and 17% of the population have some kind of insomnia at any given point in time and approximately 7% of the population have insomnia (persistent difficulty falling or staying asleep that compromises daytime functioning) of sufficient severity to warrant formal diagnosis and treatment. Insomnia affects patients of all ages and backgrounds but is especially prevalent in the elderly and in people of lower socioeconomic status.
The consequences of insomnia are significant, including impairment of work and social function, increased risk of motor vehicle accidents, and disturbance of mood.
Sleep physiology is examined by using the polysomnogram, a continuous all-night recording of respiration, eye movements, electroencephalogram (EEG), muscle tone, blood oxygen saturation, and electrocardiogram.
Normal Sleep versus Insomnia. Normal sleep can be divided into two basic phases: rapid eye movement sleep (REM) and non-REM (NREM). REM is a state of mental and physical activation. Pulse and respiration are increased but muscle tone is diminished, so little body movement occurs. The brain is active, and the EEG shows a pattern similar to that seen during waking. Most dreaming occurs during REM. In contrast, NREM is a time of deep rest. Pulse, respiration, and EEG all slow, and the patient goes from light sleep, called stages 1 and 2, to deep or delta sleep, called stages 3 and 4. REM and NREM normally cycle in a reciprocal pattern, giving a typical “architecture” to the polysomnogram. The entire cycle lasts about 90 minutes and is repeated smoothly four or five times during the night.
Insomnia is best regarded as a symptom, or complaint, which may be produced by a variety of underlying pathophysiologic processes. Therefore, insomnia has no single or pathognomonic polysomnographic pattern. Some insomniacs have slightly shorter than normal sleep times, some have less stages 3 and 4 sleep, but most have normal-appearing polysomnograms. Slight disruptions of the normal smooth cycling caused by frequent brief arousals may be related to subjectively unsatisfying sleep. Psychologic variables appear to strongly influence an insomniac’s perceptions of restfulness and sleep.
Finding the underlying problem (often there are multiple problems operating simultaneously) producing the complaint is the key to effective management of insomnia.
Psychiatric Disorders appear to be the underlying cause in about half of all cases. Among patients presenting to primary care physicians, insomnia may be the initial manifestation of depression. Patients with major depression complain of either difficulty falling asleep or of waking in the early morning and being unable to return to sleep. Diurnal variation of mood is often noted. Severe depression with agitation may lead to markedly diminished total sleep and overall exhaustion. Patients in the manic phase of a bipolar affective disorder may report difficulty falling asleep or staying asleep, but they do not report feeling tired during waking times.
Patients suffering from dysthymic disorder typically complain of feeling tired, irritable, have difficulty falling asleep, and report that they cannot get enough sleep to feel rested. Sometimes they deny feeling sad or depressed and focus only on their physical complaints. Insomnia may be their major presenting complaint.
Patients with anxiety and obsessive disorders frequently have great difficulty falling asleep because they lie in bed and ruminate. Character disorders make up about 40% of the other psychiatrically based insomnias. Patients with narcissistic or borderline character disorders characteristically feel angry or entitled and may have difficulty falling asleep. They lie in bed, furiously trying to make themselves sleep. Such patients may use their insomnia as a justification for their inability to function or to get ahead in life. Their lack of sleep is viewed as the source of all their troubles. Some even use it as a rationale for their inability to comply with the treatment of the insomnia itself.
Active psychosis of any type (e.g., schizophrenia) produces disturbed sleep and accounts for the other 10% of psychiatric insomnia. Hallucinations, delusions, and other signs and symptoms of psychotic illness present with the insomnia, facilitating recognition.
Drugs and Substance Abuse. Drugs and alcohol account for about 10% to 15% of all cases. Alcohol induces sedation, but the resulting sleep is often shallow, fragmented, and not restorative. Alcoholics can have prematurely “aged” sleep (i.e., shallow and short) during and for months after cessation of drinking.
Sedatives, especially barbiturates, when used on a regular long-term basis lead to shallow fragmented sleep. Rebound insomnia and rebound anxiety prompt reuse, and tolerance leads to dose escalation, so patients get caught in a vicious cycle. Sedatives and alcohol depress respiratory function, which can lead to very poor quality sleep in patients with sleep apnea.
Stimulant drugs such as amphetamine, pemoline, or methylphenidate; activating antidepressants (e.g., fluoxetine, sertraline, venlafaxine, desipramine, bupropion, phenelzine, protriptyline); and the phenylpropanolamine found in many over-the-counter decongestant, cold, and diet remedies can induce significant difficulty falling asleep. The caffeine and other stimulant xanthines found in tea, coffee, cola drinks, and chocolate are well recognized and often used for their ability to keep one awake. In those who are sensitive, even small amounts will prevent sleep. Nicotine and other substances found in cigarette smoke disrupt sleep induction and continuity. Bronchodilators such as aminophylline and b-agonists can make sleep difficult when given before bed.
Medical Problems are responsible in approximately 10% of cases. Chronic pain is a leading, though often overlooked, factor (e.g., that experienced by elderly persons with degenerative joint disease). Delirium is another important cause in the elderly, resulting from unrecognized infection or medication toxicity (as from anticholinergic agents used in over-the-counter sleep remedies). Cardiopulmonary dysfunction may contribute by causing orthopnea, paroxysmal nocturnal dyspnea, or nocturnal angina.
Sleep apnea is a disorder characterized by repeated apneic periods due to soft tissue upper airway obstruction followed by disruption of sleep. In severe cases, behavioral changes, pulmonary hypertension, cardiac arrhythmias, and death can occur. Patients are unaware of how disrupted their sleep is, though spouses may be kept awake by loud snoring and frightened by the apneic periods. Patients complain of marked daytime sleepiness.
Urinary frequency due to infection, prostatism, diabetes, or poor timing of diuretic use are among other important disrupters of sleep. Often, it is the nocturia and disturbed sleep that causes the patient with prostatism to finally seek definitive therapy.
Primary Sleep Disorders make up another 10% of insomnia cases. In primary or idiopathic insomnia, patients have objectively verified difficulty initiating or maintaining sleep in the absence of any identifiable underlying pathology. Such patients may need more, rather than less, sensory input to fall asleep, rather like hyperactive children who require stimulants to control their activity. Others have a persistent complaint of insomnia with no objective evidence. Although they believe they awaken, their polysomnographic studies reveal that they are actually sleeping. There is sleep state misperception. Their polysomnographic studies are entirely normal. A final group have poorly understood polysomnographic aberrations, such as the intrusion of alpha EEG into delta sleep.
In conditioned or “psychophysiologic” insomnia, patients begin to associate bedtime with frustration, anxiety, and sleep-preventing behaviors. In this learned disorder, they typically sleep very well while away from their usual bedroom (e.g., while on vacation or on the living room couch).
Circadian rhythm disorders may present with insomnia. In the delayed sleep-phase syndrome, the patient falls asleep later than the usual bedtime, sleeps well, and gets up later than is socially acceptable. This common disturbance often presents in adolescents. Other common forms are due to alternating shift work or jet travel across time zones (“jet lag”), in which the inability to rapidly reset one’s diurnal rhythm to local time leads to insomnia. For travel westward across time zones, the typical experience is awakening in the middle of night local time (morning at home) and being unable to fall back to sleep despite feeling tired. Restful sleep is not achieved. Moreover, there is marked afternoon or early evening sleepiness (bedtime at home). The inability to attain restful sleep culminates in exhaustion and the patient requests help for insomnia. Endogenous disruptions of the brain’s internal circadian rhythm setter can produce a similar picture.
Nocturnal myoclonus can produce poor quality sleep and lead to the complaint of “insomnia.” It is characterized by repetitive twitching of the legs, which is often unrecognized by the patient.