Neurology, Neuromuscular Disorders,
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Intrinsic Sleep Disorders

INTRINSIC SLEEP DISORDERS

PSYCHOPHYSIOLOGICAL AND IDIOPATHIC INSOMNIA 

Insomnia refers to the perception of insufficient sleep. This can be related to a difficulty initiating sleep, a difficulty staying asleep or the perception that the sleep quality is poor or insufficient. This condition is more commonly reported by women than men, and is more prevalent as the population ages.

Insomnia can be acute (less than a month in duration) or chronic (greater than 6 months duration) or somewhere in-between. Acute or transient insomnia is estimated to occur in about 15% of the population. Acute insomnia is often associated with physical or emotional stresses as causative factors. Psychophysiological insomnia, also known as "conditioned arousal" or "learned" insomnia, occurs when the individual associates various environmental or lifestyle stimuli with an inability to sleep. Idiopathic insomnia is a life-long innate tendency to sleep poorly.

It is helpful to understand insomnia using a framework of the three "P's": predisposing factors, precipitating factors and perpetuating factors.

Predisposing factors are the innate tendencies towards being a poor sleeper. These include personality, biologic make-up, age, coping mechanisms etc. Chronic insomnia that is caused primarily by these factors is termed idiopathic insomnia.

Precipitating factors are usually situational events, environmental or emotional stresses, or acute medical or psychological conditions that contribute to the insomnia. Stressful events in one's life such as personal loss, a new medical problem, financial problems may lead to problems with insomnia. Situational events which may precipitate an insomnia are not necessarily bad. Exciting or exhilarating events such as one's wedding, graduation, or purchase of a new car can equally serve as precipitating factors. Environmental stresses such as new construction taking place outside the home or a broken air conditioner in the middle of summer serve as precipitating factors. When these factors are the dominant influences, the insomnia is usually short-lived and ends soon after the precipitating factors are removed.

Perpetuating factors can be maladaptive behaviors, such as "trying too hard to fall asleep" and clock watching. Individuals can develop poor sleeping habits such as irregular bed-times and arise-times or taking daytime naps. Perpetuating factors can also be learned associations. These associations can happen for instance if the individual regularly does activities other than sleeping in the bed such as watching television, doing work or reading. The one thing the human brain does the best is learn. One way the brain learns is by association or pairing of different stimuli. Sometimes the brain will pair or associate stimuli that it should not such as being in bed with being awake. The individual may also develop a "performance anxiety", becoming overly preoccupied with his inability to fall asleep, which further perpetuates the sleep disturbance. When these perpetuating factors become the dominant influences on an individual's poor sleep quality, long after the initial precipitating factors have passed, the insomnia is termed "psychophysiological insomnia" or "conditioned arousal" and is frequently chronic.

OBSTRUCTIVE SLEEP APNEA

Obstructive sleep apnea is the heavy snorer's disease. Apnea refers to the cessation of breathing. In obstructive sleep apnea, the individual frequently stops breathing during sleep due to an obstruction of the airway, usually at the back of the throat. Apnea is most common in middle aged over-weight men who snore loudly. It is estimated that 20 million Americans suffer from obstructive sleep apnea. In general, obstructive sleep apnea would be present in approximately 5% of any workforce, however, certain sub-populations have considerably higher proportions. For instance, a study of long haul truck drivers found that 50% were suffering from moderate to severe obstructive sleep apnea.

As we get older and heavier, the back of the throat, called the pharynx, becomes more flexible and easily collapsible. During sleep, the muscles in the pharynx relax to make the pharynx even more collapsible. Initially, this may result in a vibration in the throat, known as snoring. Snoring is in and of itself a sleep disorderand can be very loud! Loud snoring can reach sound pressure levels of greater than 80 decibels, which even exceeds the OSHA limits for a safe workplace! Indeed loud snorers have a higher incidence of hearing loss than non-snorers. In addition, snoring has been associated as an independent risk factor in high blood pressure.

The next step past the vibration of the pharynx, is collapse. Either the airway may collapse partially or completely, either way, the individual is not getting enough air into the lungs, resulting in a drop in the concentration of blood oxygen. Fortunately, a reflex prevents the individual from asphyxiating. Oxygen detectors in the blood vessels detect the falling oxygen concentration and alert the brain. The brain has to decide between sleeping and breathing, and that is a "no-brainer"! The brain always chooses to breathe. With a snort and a gasp, the individual arouses enough for muscle tone to return to the throat and extra respiratory effort to resume breathing. As the oxygen concentration rises, the brain falls back to sleep, only to start the cycle all over again. The individual never gets the chance to fall into the deep, restful stages of sleep because of constant arousals throughout the night. Because of this restless sleep, the individual is fatigued and sleepy during the day. Additional symptoms include irritability, morning headaches and difficulty concentrating. Obstructive sleep apnea has also been identified as a causal risk factor in the development of high blood pressure due to the massive swings in pressure in the chest as the individual struggles to breathe against the closed airway. Indeed, two thirds of patients with obstructive sleep apnea will develop high blood pressure. Obstructive sleep apnea patients have a higher incidence of heart attacks, strokes and industrial and motor vehicle accidents than healthy individuals.

RESTLESS LEGS SYNDROME (RLS) and PERIODIC LIMB MOVEMENTS OF SLEEP (PLMS)

Restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) are two distinct entities, however, because they frequently overlap they are both discussed here.

RLS is a common disorder, which actually occurs in wakefulness, and frequently leads to difficulty initiating sleep. It often runs in families. The condition consists of abnormal and uncomfortable sensations primarily in the legs. The arms can also be affected. These sensations are often vaguely described as creeping feelings deep with in the limbs associated with an irresistible urge to move the limbs. Bedtime is particularly a problem with individuals with RLS because the abnormal sensations and the irresistible limb movements worsen when in the relaxed and recumbent position, as when getting ready to fall asleep. Frequently these individuals will awaken in the night with the same sensations and have to stretch, rub, flex or move the limbs vigorously. At times they must get out of bed to "walk off" the symptoms. RLS was initially thought to occur in about 5% of the population, however, more recent reports indicate that this is probably an underestimation. RLS not only affects the individual suffering from the condition but also can affect the bed partner. In 25% of all cases of RLS seen at one sleep center, the referral was due to complaints by the bed partner due to the incessant nocturnal movements. One third of those couples were sleeping in separate beds due to the disorder.

PLMS can occur with RLS or alone. The condition is a movement disorder, which occurs during sleep. Throughout the night, the individual has rhythmic stereotyped movements of the affected limbs, again more commonly the legs. These kicking movements consist of an upward flexion of the toe and foot, and can involve the knee and hip as well. They are brief, lasting between 1/2 second to 5 seconds, occurring about every 20 to 40 seconds. The movements can cluster into episodes that can last several minutes to hours. When the movements are brisk, they can result in brief arousals or awakenings throughout the night leading to restless and non-restorative sleep. PLMS can occur in individuals who do not complain of a sleep problem; however, studies have found PLMS to be the major sleep abnormality in 11 to 17 percent of individuals complaining of restless sleep or excessive daytime sleepiness.

Although these conditions are treatable medically, few individuals suffering from them seek treatment. First, they frequently do not recognize the condition as a problem that has a solution, attributing a "That's just the way I am" philosophy. Second, the condition is little known to general physicians, thus going undiagnosed. Educational programs can help alert workers with sleep problems to the signs and symptoms of these disorders and direct them to the proper medical attention.

NARCOLEPSY

Narcolepsy is a primary disorder of excessive daytime sleepiness. It is an inheritable condition which, in large part, consists of dysfunction of the rapid eye movement (REM) stage of sleep. Narcolepsy is not rare. The condition is estimated to occur in 250,000-375,000 Americans, making it about as common as Parkinson's Disease or Multiple Sclerosis. This lifelong condition can begin any time from childhood to the late 40's. The peak age of onset is in the teens, with a second smaller peak between 35 and 45 years of age. The syndrome of Narcolepsy consists of excessive daytime sleepiness and overwhelming episodes of sleep; cataplexy (sudden loss of muscle tone); sleep paralysis (awakening from sleep finding oneself unable to move for a few minutes); and hypnagogic hallucinations (dreamlike images that occur at the onset of sleep). Frequently, sufferers of Narcolepsy will also complain of disrupted sleep at night as well.

REM stage of sleep is the stage in which we dream. It is characterized by complete muscle relaxation. In individuals with Narcolepsy, features of REM sleep intrude into wakefulness. In addition to the excessive sleepiness that intrudes into the daytime hours impairing concentration and attention and at times leading to frank unconsciousness, individuals with Narcolepsy often have attacks of cataplexy or sudden loss of muscular tone. These attacks are usually triggered by an emotionally charged situation such as hearing bad news or a funny joke. Cataplectic attacks can result in falls to the ground or sudden weakness resulting in a transient weakness of the arms. This can lead to injury if the individual is operating machinery or lifting and carrying.

Unfortunately, due to lack of physician awareness of the condition and its symptoms, the symptoms of Narcolepsy may go on for years before an accurate diagnosis is made. The average time from onset of symptoms to diagnosis of Narcolepsy is 15 years! In that time, the individual will have gone to an average of five physicians in search for an explanation of the symptoms. Narcolepsy is also a medically treatable condition. When properly diagnosed and treated most individuals with Narcolepsy can return to a functional and productive life.