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Reasons Why You Feel Sleepy

Sleep Apnea, Narcolepsy, and Other Disorders May Cause Excessive Sleepiness

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Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

If you have trouble staying awake, suffer from excessive daytime sleepiness, easily doze off, take naps on a regular basis, and have difficulty with attention or concentration, you may wonder: Why do I feel sleepy? Some sleep disorders, such as insomnia, make it so you can't sleep, while many others result in poor sleep. Here are some possible reasons why you feel sleepy.

1. Poor Sleep Hygiene

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The most common cause of feeling too sleepy might be the most obvious: not getting enough sleep. You may simply not know how much sleep you need. And if you do know, you may choose to not sleep enough, which is sometimes called sleep restriction. You could be trying to sleep in a poor sleep environment that is not conducive to sound sleep. You may have a horrible bedtime routine that does not prepare you well to fall asleep. You may also fail to follow any of the other simple guidelines to improve your sleep. Any and all of these things may leave you too sleepy the next day, without any specific sleep disorder as the cause.

2. Sleep Apnea

Sleep apnea is a condition in which you repeatedly stop breathing while asleep. This results in a loud snort and brief awakening as you gasp for air. This may occur dozens or even a hundred times per hour of sleep. With each awakening, you shift briefly into lighter stages of sleep. This disruption leads to sleep fragmentation and results in significant excessive daytime sleepiness. People with severe sleep apnea are at risk for falling asleep while driving.

A similar condition called upper airway resistance syndrome (UARS) can also be problematic. There are also serious health consequences to sleep apnea, so treatment should be pursued.

3. Narcolepsy

There are four defining symptoms of narcolepsy, the least specific being excessive sleepiness. This sleep disorder occurs when there is a problem with the regulation of sleep and wakefulness. Therefore, characteristics of sleep may suddenly occur while awake (such as paralysis) and elements of wakefulness may intrude upon sleep. The most characteristic symptom is cataplexy, which is the sudden loss of muscle tone with emotional stimulus such as surprise or laughter. The sleepiness associated with narcolepsy may require treatment with stimulants such as Ritalin, Provigil, and Nuvigil.

4. Chronic Fatigue Syndrome

Chronic fatigue syndrome is a condition that might make you feel sleepy. It is characterized by worsened fatigue that occurs after exertion, associated with unrefreshing sleep and often joint and muscle pains. Although the cause of chronic fatigue syndrome is not completely understood, it can lead to significant impairment and disruption of the affected person's life.

5. Kleine-Levin Syndrome

Although quite rare, Kleine-Levin syndrome is a condition that may affect young adults and can cause recurrent episodes of excessive sleepiness. These episodes can last for days, weeks, or even months at a time. The sleepiness can be incapacitating. There may be associated symptoms, such as hallucinations or hypersexual or compulsive behaviors. The only treatment known to be beneficial in the treatment of Kleine-Levin syndrome is the mood stabilizer called lithium.

6. Restless Legs Syndrome

Disorders that cause excessive movements during sleep may lead you to feel sleepy the next day. The most common condition is restless legs syndrome (RLS). This disorder is characterized by an uncomfortable sensation in the legs that often develops in the evening as you are lying down to rest and is relieved by movement.

A commonly associated condition, called periodic limb movement syndrome (PLMS), is diagnosed when there are sudden jerking movements that occur during sleep. There are effective treatments available for these conditions.

7. Circadian Rhythm Disorders

Various circadian rhythm disorders may leave you feeling too sleepy. The circadian rhythm is the body's natural clock that helps to coordinate your activities to the timing of light and dark in your environment. If this timing is misaligned, you may find yourself sleepy at inappropriate times.

For example, if you have advanced sleep phase syndrome, you will feel sleepy in the evening. Conversely, with delayed sleep phase syndrome, you will have difficulty falling asleep and feel sleepy in the morning. Fortunately, there are effective treatments for these and other circadian rhythm conditions, such as jet lag and seasonal affective disorder (SAD).

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