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Causes of Excessive Sleepiness

Danielle Pacheco

Written by

Danielle Pacheco, Staff Writer

Dr. Anis Rehman

Medically Reviewed by

Dr. Anis Rehman, Endocrinologist

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Do you notice yourself feeling tired all the time, or sometimes falling asleep during the daytime when you’d prefer to be awake? Excessive daytime sleepiness, also called drowsiness, can majorly interfere with your life. When you feel excessively sleepy, you might doze off at inappropriate times. For example, you could find yourself falling asleep during a work meeting or while driving. As a result, excessive sleepiness can create personal problems or even become dangerous.

Excessive sleepiness is generally considered a symptom or side effect rather than a primary disorder. Most people who have excessive sleepiness also have an underlying issue causing their drowsiness, even if they aren’t aware of it. Pinpointing the cause of one’s excessive sleepiness is the first step toward overcoming it.

What Is Excessive Sleepiness?

Excessive sleepiness refers to the urge or tendency to fall asleep when you want to be awake, such as during daytime hours. Many people commonly experience excessive sleepiness. Research shows that up to 37% of the U.S. population reports experiencing excessive sleepiness at least a few days each month, with fewer people experiencing it more often.

Although excessive sleepiness overlaps with fatigue, it is a distinctly different symptom. When a person experiences excessive sleepiness, they tend to nod off or fall asleep when they want to be awake. When a person experiences fatigue, they often feel tired but do not usually fall asleep when they want to be awake.

Excessive sleepiness is often referred to as excessive daytime sleepiness, or EDS, by physicians and sleep specialists. To eliminate or reduce your EDS, you must first figure out why you are experiencing it.

Why Do I Have Excessive Sleepiness?

If you experience excessive sleepiness, you’ve probably asked yourself, “Why am I so sleepy during the day?” There is no single, universal answer to that question because different people experience excessive daytime sleepiness (EDS) for various reasons.

Research shows people experience EDS as a result of a wide variety of underlying causes, such as:

  • Sleep deprivation due to lifestyle, jet lag, or sleep problems
  • Sleep disorders such as obstructive sleep apnea and narcolepsy
  • Disturbed sleep due to environmental disruptions
  • Neurological disorders such as Parkinson’s and epilepsy
  • Psychiatric disorders such as depression and anxiety
  • Health problems such as heart and liver failure
  • Medications such as pain medications and alcohol

If you don’t have health or psychiatric problems that could be causing your EDS, consider exploring the possibility of a sleep disorder. Since poor sleep causes sleepiness, EDS is a symptom of multiple sleep disorders.


What Sleep Disorders Commonly Cause Excessive Sleepiness?

Many sleep disorders commonly cause EDS. Have you found yourself wondering, “Why am I so tired all the time?” If so, consider seeing a sleep specialist to determine if you have a sleep disorder. Talking to your doctor about your symptoms is the best way to start the process of understanding your personal causes of sleepiness, whether or not a sleep disorder is a factor.

People with the following sleep disorders commonly experience EDS:

  • Obstructive sleep apnea is a disorder in which the airway closes during sleep, causing a person to stop breathing and temporarily wake up — sometimes without being aware of doing so — multiple times throughout the night
  • Restless leg syndrome is a disorder that causes abnormal sensations and a strong desire to move the legs, especially in the evening or while lying down, which can interfere with falling asleep or cause nighttime awakenings
  • Periodic limb movement disorder is a disorder in which a person experiences frequent leg or arm twitching during sleep
  • Circadian rhythm sleep disorders, such as jet lag or shift work sleep disorder, cause a person’s internal sleep-wake clock to mismatch with the daily sun schedule, so they are less likely to feel tired at night or alert during the day
  • Narcolepsy is a disorder characterized by excessive sleepiness in which a person falls asleep easily during the day, sometimes completely losing muscle tone (cataplexy), and often experiences disturbed sleep at night.
  • Parasomnias are a variety of disorders that involve unwanted experiences during sleep or while falling asleep, such as sleepwalking (somnambulism), night terrors, nightmares, sleep-related leg cramps, and rapid eye movement (REM) behavior disorder
  • Menstrual-related sleep disorder involves sleep problems, such as excessive daytime sleepiness and insomnia, that occur only in the days leading up to menstruation, likely due to hormonal changes
  • Idiopathic hypersomnia is a diagnosis given when a person is sleepier or requires more sleep than is considered normal but isn’t found to have any other underlying sleep disorders
  • Insomnia describes a symptom in which a person has trouble sleeping at night, often due to an underlying condition or other issue

Of the many sleep disorders that can cause EDS, only two present primarily as excessive sleepiness: narcolepsy and idiopathic hypersomnia. That said, sometimes a person isn’t aware of their other symptoms, so you can’t assume you have a specific sleep disorder because you believe you experience excessive sleepiness alone.

For example, a person with obstructive sleep apnea might not realize they stop breathing during the night, and someone with periodic limb movement disorder might not realize they often twitch while asleep. You may need a professional to identify the cause of your excessive sleepiness.

Identifying and Treating Causes of Excessive Sleepiness

Learning the cause of your excessive sleepiness is essential because of the significant toll excessive sleepiness can take on your life. Excessive sleepiness in adolescents can negatively impact their school performance, personal relationships, overall health, and driving ability. In adults, excessive sleepiness can greatly affect their work, leading to lower productivity, more absent days, and even an increased risk of on-the-job accidents.

If you’re experiencing excessive sleepiness, tell your doctor. They should work with you to determine the cause and identify appropriate treatments. To diagnose underlying problems, your doctor might:

  • Ask questions about your sleep quality, sleep habits, and daytime drowsiness concerns
  • Ask questions about your medical history, including any past psychiatric diagnoses
  • Ask you to complete a questionnaire rating the sleepiness you feel at different times of day
  • Order a sleep study
  • Order other medical tests or refer you to another type of doctor

Depending on what comes out of your examination, your doctor will likely recommend one of the following treatments for EDS:

  • Improved sleep hygiene, such as a consistent bedtime and nighttime routine
  • Treatment for underlying sleep disorders, such as a continuous positive airway pressure (CPAP) machine for obstructive sleep apnea or sleep medications for other disorders
  • Evaluation by a physician to treat underlying disease
  • Medications that promote wakefulness
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About Our Editorial Team

Danielle Pacheco

Staff Writer

Danielle writes in-depth articles about sleep solutions and holds a psychology degree from the University of British Columbia.

Dr. Anis Rehman



Dr. Rehman, M.D., is a board-certified physician in Internal Medicine as well as Endocrinology, Diabetes, and Metabolism.


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