Welcome to the California Center for Sleep Disorders

Daytime Sleepiness

Introduction

Excessive daytime sleepiness is extremely common in our society. The commonest cause by far is an inadequate amount of sleep. Most of us do need about 8 hours or more to be fully rested. Surprisingly, many people do not actually recognize that they are sleepier than they should be. They become accustomed to being sleepy and consider it normal. You can help yourself determine if you are sleepier than normal by taking the Epworth Sleepiness Test. If you are sleepy despite getting an adequate number of hours of sleep, it is very likely that you have a sleep disorder. While there are a large number of such disorders, a few are much more common as a cause for sleepiness:

Narcolepsy
Restless Legs Syndrome/Periodic Leg Movements in Sleep
Obstructive Sleep Apnea (OSA)
Insomnia

Importance of daytime sleepiness in society

Dangerous sleepiness can occur in anyone, not just people with serious sleep disorders. A study by the Center for Traffic Safety at the University of North Carolina Highway Safety Research Center determined that as many as 15% of all vehicle accidents are due to falling asleep, or fatigue-related inattentiveness, at the wheel.

Traffic accidents are a major cause of death, injury and property loss. More and more studies are finding that falling asleep at the wheel is a major factor, perhaps the most important after alcohol, in causing traffic accidents. Fatigue-related traffic accidents usually involve no more than one or two vehicles. Yet, they are the most destructive of all to life and property, probably because the drivers are so inattentive that they do not slow down before the crash. The time at which fatigue-related traffic accidents occur shows a pattern with two peaks: one between midnight and 3 AM and one between 2 and 5 PM. When scientists asked people to try and fall asleep periodically throughout the day, they found that sleep tendency in normal humans also has the same two-peak pattern with an early morning and a late afternoon high point. When we get too little sleep or take any substance that causes sleepiness, these periods of increased sleep tendency can be transformed into periods when bouts of unintentional sleep occur. These bouts of sleep may be experienced as harmless, brief lapses in attention, but they can also lead to disaster.

Modern day problems of sleep-related accidents extend beyond highway travel to industry as well. Throughout recorded history, many people have decided, or been forced, to cut back on their sleep and have often fallen asleep on the job. What is worrisome is that nowadays so many more people can be hurt by a sleepy or inattentive worker than even a hundred years ago. For example, when a train driver or a nuclear power engineer falls asleep on the job, the result can be catastrophic in terms of the loss of life and property. When a stagecoach driver fell asleep on the job in the 1800's, the lapse might even have gone unnoticed. The major reason for increased interest in sleep is that, in the 1900's, too much sleep in the work environment and too little sleep at home have become dangerous to all of us. In industries where people must work round the clock, scientists find that workers -- particularly those workers on evening and graveyard shifts -- may not always be sufficiently rested to function with necessary alertness. The nuclear accidents at Three Mile Island and Chernobyl both arose from mistakes that occurred between midnight and 3 AM. And, the decision to launch, which lead to the Space Shuttle disaster on January 28, 1986, came during this same early morning peak in sleepiness. Moreover, the NASA officials involved in that decision were seriously overworked and sleep-deprived.
Thus, on the road and in the work place, it is important to respect your sleep need and recognize the signs of excessive sleepiness, such as lapses in attention, that may actually be unintentional bouts of sleep.

Narcolepsy

Narcolepsy is a disorder involving a chemical imbalance in the brain cells that control wakefulness and sleep. The disorder can run in families or appear as an isolated problem affecting only one individual in a family. Narcolepsy, after sleep apnea, is the second most common cause of the symptom of disabling daytime sleepiness. Narcolepsy is not rare in humans. Afflicting about 1 of every 2000 people throughout the world, narcolepsy is about as common as Multiple Sclerosis. Several symptoms are characteristic of narcolepsy:
The patient suffers from excessive daytime sleepiness, with the possibility of a "sleep attack" -- at mealtime, at the theater -- really anywhere. The patient can often fight this sleepiness for awhile but eventually the sleepiness is overwhelming. A short nap may restore wakefulness temporarily.

Narcolepsy involves the abnormal intrusion of part or all of rapid eye movement or dream sleep (REM sleep) into wakefulness. Narcoleptic paralysis is involuntary and can come under two circumstances:

(a) cataplexy -- sudden muscle weakness leading to partial or complete collapse precipitated by excitement or an emotional response, most frequently laughter.

(b) sleep paralysis -- an often frightening inability to move just before falling asleep or upon awakening.

The hallucinations of narcolepsy are known as hypnagogic hallucinations. These hallucinations also depend on REM sleep mechanisms and come as sometimes benign, sometimes terrifying apparitions just as the narcoleptic falls asleep or just as they are awakening.

Animal forms of narcolepsy exist and can be passed genetically from parents to offspring, complete with abnormal sleepiness and cataplexy. Narcolepsy has been described in species such as dogs and horses. There are also reports of people getting narcolepsy after a disease or an injury to the brain. But the few carefully-studied cases of this 'acquired narcolepsy', indicate that there is no single disease of 'acquired narcolepsy', just various medical conditions with few real and sustained similarities to narcolepsy.
Exciting genetic discoveries have recently been made involving animal models of narcolepsy. Stanford University scientists identified a mutant gene that causes narcolepsy in dogs. The normal gene is called the hypocretin receptor 2 gene. The abnormal gene disrupts communications between neurons that use the neurotransmitter, hypocretin 2.
Working independently, a group in Dallas, TX and Boston, MA created a mouse strain that cannot produce hypocretin. This knock-out mouse has the symptoms of narcolepsy. It is expected that, because of the high degree of conservation across species in the hypocretin system, genetic defects affect hypocretin communication will be found to cause narcolepsy in some humans. However, it is not likely that defects in the hypocretin system will explain all narcolepsy because there are familial forms, non-familial forms and post traumatic forms.

The new anti-narcolepsy drug, modafinil, is chemically different from other drugs used to treat the sleepiness of narcolepsy. Modafinil, as well as older stimulant drugs activate hypocretin-containing neurons. These drug effects support the idea that hypocretin is somehow involved in the control of sleep.

Recent genetic studies have linked narcolepsy to certain genes at a particular location, called the Major Histocompatibility Complex, on chromosome number 6. The two genes most often studied because of their linkage with narcolepsy are those that produce the HLA-DR15 and HLA-DQ6 antigens found on the surface of white blood cells. Exhaustive research indicates that the gene which produces the specific HLA-DQ antigen called, HLA-DQB*0602, seems to be a true narcolepsy susceptibility gene. However, about 20 - 30 percent of the population have this gene and only about 0.05 percent of the population have narcolepsy. This means that other genes or environmental factors are necessary for narcolepsy to develop in people with the HLA-BQB*0602 gene. Since several genes in the Major Histocompatibility Complex have been linked to diseases of the immune system, there is currently much research on the genetic and the immunological make-up of narcoleptics and their families. To date, family studies of patients with narcolepsy have shown that in families where multiple members have narcolepsy, the HLA-DQB*0602 gene tends not to be present, indicating that familial forms of narcolepsy are caused by another gene or genes.

There is no cure, as yet, for narcolepsy. The symptoms of narcolepsy are controlled with a 'double barreled' approach: (a) Several daytime naps and stimulants, such as amphetamines, control the abnormal tendency to fall asleep at inappropriate times; (b) Other drugs that suppress REM sleep such as antidepressants, help control the symptoms of cataplexy, sleep paralysis and hypnagogic hallucinations.

Obstructive Sleep Apnea

This condition affects from 2-4% of the adult population. More here.

Restless Legs Syndrome (RLS) and Periodic Movements in Sleep (PLMS)

These conditions, which are also relatively common, may just be a slight annoyance to many, but in some sufferers have a huge impact on their quality of sleep. RLS is a condition of unknown cause that leads to an uncomfortable, creepy crawly, sometimes almost painful sensation in the patient's legs and less frequently arms. The sensation usually occurs when the patient lays down to sleep, and may be uncomfortable enough to cause them to move around, shake their legs, even get out of bed and walk. It may lead to great difficulty falling asleep. Once asleep these patients usually continue to have leg movements and jerks through much of the night. In many cases these are sufficient to briefly interrupt sleep. The result is often a less than restful nights sleep and resulting daytime sleepiness. Occasionally this can be almost disabling.

While we have generally thought of this as a disease that increases with age, we have begun to recognize its presence in younger patients and children. In some there seems to be a strong genetic component.

While the mechanism of leg movements is unknown, recent research has suggested a link to deficient body iron stores. This can sometimes be detected by measurement of serum ferritin, an iron binding protein in the blood. Low or low normal levels should suggest that a trial of iron treatment is warranted with many patients found to benefit.

In others, a variety of medications are available which often help. Currently the most popular group of medications include drugs used for Parkinson's Disease, though there is nothing to suggest this condition is associated with RLS/PLMS. In addition, sedatives and analgesics (narcotics) have been used with success.

Insomnia

When sleep is severely disrupted for any reason, resulting daytime sleepiness may occur. See the section on Insomnia.