Excessive daytime sleepiness (EDS) occurs when a person experiences regular periods of tiredness and drowsiness throughout the day. People with narcolepsy always experience EDS.

EDS can cause a person to experience recurrent episodes of daytime sleepiness.

It is a common condition that affects approximately 10–20% of the population. One common cause of EDS is narcolepsy.

In this article, we look at what EDS is and its possible causes. We also explain how healthcare professionals diagnose and treat EDS.

A person sleeping on a seat while traveling on public transport. They may have narcolepsy.Share on Pinterest
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A person who has EDS will regularly experience significant drowsiness and tiredness, even if they get the recommended amount of sleep.

Hypersomnia” is another name for EDS. Common symptoms of EDS include:

  • recurrent episodes of daytime sleepiness
  • prolonged nighttime sleep
  • difficulty waking from a long sleep
  • disorientation
  • anxiety
  • irritability and restlessness
  • lack of energy
  • slow thinking
  • slow speech
  • loss of appetite
  • hallucinations
  • memory problems

A person with EDS may also have the compulsion to nap repeatedly during the day, often at inappropriate times, such as during a meal or while at work. These naps often do not relieve EDS symptoms.

EDS can also cause a person to have difficulty carrying out their daily activities.

Narcolepsy is a chronic neurological condition that causes a person to experience fragmented sleep and the quick onset of rapid eye movement (REM) sleep.

According to the National Institute of Neurological Disorders and Stroke, all individuals with narcolepsy experience EDS.

EDS is often the most obvious symptom of narcolepsy.

People with narcolepsy often experience EDS as a “sleep attack,” which occurs suddenly. They may experience EDS episodes that persist for a few seconds or several minutes. These episodes may vary in frequency and can occur several times in a single day.

EDS has several possible causes, including:

Narcolepsy is another common cause of EDS. People with narcolepsy often experience EDS as a sleep attack and may have their usual levels of alertness between these attacks.

Healthcare professionals do not yet know the exact cause of narcolepsy. Some link narcolepsy to the naturally occurring chemical hypocretin, which promotes wakefulness and regulates REM sleep.

Studies suggest that low hypocretin levels may be the main cause of narcolepsy symptoms.

Learn more about the pathophysiology of narcolepsy.

To diagnose EDS, a healthcare professional may ask:

  • how long a person has experienced EDS
  • how long a person sleeps on weekdays and weekends
  • how often a person wakes up during the night
  • whether a person has experienced any changes in their work or personal life that may affect their sleep

A healthcare professional will want to determine the cause of the person’s EDS. They may also wish to determine whether it is medical or behavioral.

They may carry out a physical examination and order lab tests to check for underlying causes.

To find the cause of a person’s EDS, a doctor may also ask the person to undergo a polysomnogram (PSG). This is a type of sleep study that often takes place at a hospital or sleep center.

While a person sleeps, a PSG measures their:

The results of a PSG can help a doctor determine whether an underlying condition is causing a person’s EDS.

If healthcare professionals suspect that narcolepsy is the cause, they may follow up with an additional daytime sleep test called a multiple sleep latency test (MSLT) to find out how sleepy a person is during waking hours.

Doctors may also refer to an MSLT as a daytime nap study, as it measures how long it takes for a person to fall asleep during the daytime.

During an MSLT, a person takes four or five naps about 2 hours apart, with sensors measuring how long it takes them to fall asleep and to enter REM sleep. People who enter two or more REM sleep stages during the MSLT typically have narcolepsy.

Learn more about what happens during a sleep study.

The treatment for EDS will depend on the cause.

If a person’s EDS has behavioral causes, then their doctor may recommend that they try some lifestyle strategies such as:

  • going to bed at the same time each night and getting up at the same time each morning
  • ensuring that their bedroom is quiet and dark
  • ensuring that their bedroom is always at a comfortable temperature
  • removing electric devices such as TVs and phones from their bedroom
  • not eating large meals before bed
  • avoiding caffeine and alcohol before bed
  • avoiding tobacco, which contains nicotine
  • exercising regularly and being physically active during the day

Learn more about tips for good sleep habits.

If a person’s EDS has an underlying cause, then their doctor will want to treat this cause first.

Treating EDS that results from narcolepsy

Narcolepsy currently has no cure, but some medications can help treat the symptoms. These include:

If a person is regularly experiencing symptoms of EDS, they should contact a healthcare professional. A healthcare professional can help treat the symptoms of EDS, but they will also want to discover the cause of the symptoms.

They may suggest that the person see a sleep specialist, a doctor who diagnoses and treats sleep disorders.

EDS causes a person to regularly experience significant drowsiness and tiredness throughout the day.

It is often a symptom of another condition, such as insomnia, RLS, or sleep apnea. Another possible cause of EDS is narcolepsy. All people with narcolepsy experience EDS.

EDS can also result from behavioral factors. A person may be able to reduce EDS symptoms by making certain lifestyle changes to improve their sleep.

If a person’s EDS is a result of another condition, a doctor will want to treat that condition to improve the EDS symptoms.

Narcolepsy currently has no cure, but certain medications can treat the symptoms.