Secondary, or comorbid, insomnia results from or coexists with another illness or condition. Examples of such disorders that can bring about secondary insomnia include: medical conditions, neurologic derangements, substance abuse, anxiety, depression, adjustment problems, and bipolar disorder. When evaluating a patient with sleep problems, it is important to explore a variety of factors.18
Depression
Data suggest that insomnia predicts future psychiatric disorders, including major depression, anxiety, and alcohol abuse.19-25 The link between insomnia and depression is so strong that depression is always included in the differential workup of a person with deranged sleep. The onset of insomnia commonly precedes depression. However, the same relationship does not apply to other psychiatric disorders. Patients who exhibit major depression are more likely to be suicidal if they cannot sleep.26,27
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Substances and medications
Although alcohol induces sleep quickly, it is not beneficial because alcohol is metabolized in the body rapidly, causing a withdrawal reaction that awakens the person. Caffeine is a short-acting substance but is best avoided after 2:00 pm.
Medications that can cause insomnia include antidepressants, antihypertensives, antineoplastics, hormones, and decongestants.28
Medical conditions that affect sleep
Respiratory disorders. Sleep can intensify the predisposition for diminished blood oxyhemoglobin saturation levels in patients with COPD, asthma, and other respiratory illnesses. Low arterial oxygen saturation levels can result in CNS irritability and poor sleep quality. Obstructive sleep apnea (OSA) is commonly characterized by poor sleep quality and interrupted sleep, daytime sleepiness, and snoring. The underlying cause is a functional collapse of the airway that occurs because of a derangement in the sleep mechanism that normally stimulates the pharynx to remain open at night.29,30
Gastroesophageal reflux disease (GERD). The arousal process is important in producing proper acid clearance from the esophagus in patients with an incompetent lower esophageal sphincter, the basis of GERD.31,32
Geriatric conditions. Prostate difficulties, which can force multiple trips to the bathroom at night, are a leading cause of insomnia in older men.31,32
Restless leg syndrome (RLS). Patients with RLS have an uncontrollable urge to move their extremities, which is often accompanied by sensations of itching, burning, crawling, and cramping in the legs and other body parts. These sensations intensify at night and can awaken the patient.31,32
Circadian rhythm sleep disorders
Circadian-rhythm sleep disorders result from externally imposed sudden changes in sleep-wake times to which internal clocks cannot adapt properly. This type of disorder can also be caused by aberrations of the biological-clock mechanism itself. Other functions that follow a circadian pattern include body temperature, melatonin production, cortisol release, kidney output, and hormone regulation.33-35
Jet lag and shift-work sleep disorder
Jet lag occurs after travel across at least two time zones and can often be accompanied by malaise and GI disturbances. It is presumed to result from a mismatch between the body’s rhythms and those of the environmental cycle, as well as a desynchronization between the various endogenous rhythms. In shift-work sleep disorder, the body is forced to change rhythms too rapidly and cannot adjust in a timely manner to repeated changes in sleep-wake times.33-36
There are four guiding principles to help counteract the effects of jet leg and shift work:33-36 (1) Adjust rhythms gradually in increments of no more than three hours from one day or one shift to the next; delay and do not advance the sleep schedule whenever possible. (2) Plentiful exposure to light during waking hours helps body rhythms to resynchronize quickly; sleeping in a darkened room is helpful. (3) Take brief naps when sleepy; however, naps should occur at the same time every day to avoid confusing circadian rhythms. (4) Keep sleep schedules as constant as possible, especially during shift work; sleep should occur at the same time every day, including days off and weekends.
Irregular sleep-wake rhythm
Irregular sleep-wake rhythm is characterized by chronic insomnia and multiple (three or more) bouts of sleep that occur during a 24-hour period. The repetitive pattern of sleeping and waking is involuntary. Although the cause of this disorder is unknown, it is more commonly seen in the elderly and those patients suffering from dementia or head trauma.33,35
Delayed and advanced sleep disorder
Delayed sleep-phase syndrome occurs primarily in children and adolescents. In this disorder, the timing of sleep is delayed relative to the usual day/night cycle. Affected persons are unable to fall asleep if they do go to bed earlier at night. Treatment for this disorder consists of good sleep hygiene and exposure to bright, artificial light in the morning. The schedule of light exposure is gradually advanced across one or two weeks until the child is falling asleep earlier in the evening.35-37
Those with advanced sleep-phase syndrome fall asleep early and wake up early. The elderly tend to be affected more than any other age group. Treatment for this disorder involves exposure to bright light in the evening and avoidance of early morning light.35-37
Free-running circadian rhythms
Patients suffering from free-running circadian rhythms are confronted with several days of insomnia followed by sleep periods that endure from 14 to 18 hours a day. After patients with this disorder awaken from these lengthy stretches of sleep, they are unable to fall back asleep for one day. Free-running circadian rhythms are more prevalent among the blind, which appears to support the theory that this particular disorder is caused in part by an absence of a light signal to the suprachiasmatic nucleus (SCN), a key region of the body’s sleep-regulating mechanism.35-37
Evaluation
When evaluating a person who has insomnia, obtaining a thorough medical and psychiatric history is necessary. Determine the pattern of insomnia and find whether it is related to any life event or changes in environment. Inquire as to the patient’s treatment with medication and consumption of caffeine or alcohol. Discuss the patient’s sleep habits and patterns, such as being a light or heavy sleeper. Inquire as to whether there is a family history of insomnia. An indication of an underlying psychological or psychiatric condition may necessitate further testing.
A physical examination is an important element of the patient’s workup. Test for diabetes, heart disease, GERD, RLS, and respiratory conditions, including allergies, asthma, OSA, and COPD.
Examine the patient’s lifestyle: inquire about his or her travel and work schedule, exercise, eating habits, and activities prior to going to bed. Ask the patient about keeping a sleep log, wherein the person records the 24-hour sleep-wake cycle patterns over a two-week period.38
Referral
The results of a thorough medical evaluation may indicate the need to refer the patient to a sleep specialist. This is especially true when the patient has been diagnosed with OSA or severe daytime sleepiness or exhibits dangerous nocturnal behaviors.
Treatment
Internal and external factors can influence an individual’s ability to fall asleep and remain asleep. Whatever initiates the episode usually does not perpetuate the symptoms. Therefore, the best strategy for treating patients with insomnia involves an integrated combination of psychological interventions, behavioral changes, and possibly pharmacologic therapy.
Nonpharmacologic treatment
Good sleep hygiene. Proper sleep hygiene includes maintaining regular sleep-wake hours. Homeostatic and circadian processes predispose a patient to sleep at a particular time. Individuals must listen to their body and not to fall into the “nap trap,” which can diminish the homeostatic drive that helps one fall asleep and stay asleep at the proper bedtime. Napping can perpetuate insomnia.
Advise patients to keep caffeine intake to a minimum (especially after lunch) and to beware of the effects of alcohol, which tends to be hyperarousing.
A small snack may be conducive to sleep; however, large or heavy meals just before bedtime can interfere with sleep, especially in a person who suffers from a reflux disorder.
