The Epworth sleepiness scale (ESS) is a self-administered questionnaire that’s routinely used by doctors to assess daytime sleepiness. The person filling in the questionnaire rates how likely they are to doze off during the day in different situations.

The ESS was developed in 1990 by Australian doctor Murray Johns and named after the Epworth Sleep Center he established in 1988.

The questionnaire was created for adults, but it’s been used successfully in various studies of adolescents. A modified version — the ESS-CHAD — was created for children and adolescents. This version is similar to the adult ESS, but the instructions and activities have been changed slightly to make it more relatable to children and adolescents and easier to understand.

Daytime sleepiness may be a sign of a sleep disorder or underlying medical condition. The questionnaire may be used to help your doctor diagnose a sleep disorder or to monitor your response to treatment.

The ESS consists of eight questions. You’re asked to rate your usual chances of having dozed off or fallen asleep while engaged in different activities on a scale of 0 to 3. The activities included in the questionnaire are:

  • sitting and reading
  • watching TV
  • sitting inactive in a public place, such as a meeting or theatre
  • riding as a passenger in a car for an hour without a break
  • lying down to rest in the afternoon when circumstances permit
  • sitting and talking to someone
  • sitting quietly after a lunch without alcohol
  • sitting in a car, stopped for a few minutes in traffic

These activities vary in their somnificity, which is a term introduced by the creator of the ESS. It describes how different postures and activities impact your readiness to fall asleep.

Your scores provide estimates of how likely you are to fall asleep during routine situations in your daily life. The higher your score, the higher your daytime sleepiness.

You can download the ESS questionnaire from the America Sleep Apnea Association or through Division of Sleep at Harvard Medical School.

Each of the activities listed has an assigned score from 0 to 3 that indicates how likely a person is to fall asleep during the activity:

  • 0 = would never doze
  • 1 = slight chance of dozing
  • 2 = moderate chance of dozing
  • 3 = high chance of dozing

Your total score can range from 0 to 24. A higher score is associated with increased sleepiness.

The following shows how your score is interpreted:

  • 0 to 10 = normal range of sleepiness in healthy adults
  • 11 to 14 = mild sleepiness
  • 15 to 17 = moderate sleepiness
  • 18 to 24 = severe sleepiness

A score of 11 or higher represents excessive daytime sleepiness which could be a sign of a sleep disorder or medical condition. If you score 11 or higher, your doctor may recommend you see a sleep specialist.

The following are some conditions that can cause excessive daytime sleepiness.

  • hypersomnia, which is excessive daytime sleepiness even after a long night of sleep
  • sleep apnea, in which you stop breathing involuntarily for brief periods during sleep
  • narcolepsy, a neurological disorder that causes sleep attacks in which a person can fall into and wake from REM sleep at any time of day during any activity

Excessive daytime sleepiness can also be caused by:

The validity of the ESS has been established in multiple studies and in correlation with objective sleepiness tests, such as the multiple sleep latency test (MSLT). While it’s been shown to be a reliable way to measure daytime sleepiness, there’s evidence that it may not be a reliable predictor of sleep disorders, such as sleep apnea and narcolepsy.

The test has proven to be an effective screening tool, but isn’t meant to be used as a diagnostic tool by itself. This is because it can’t distinguish which sleep disorders or factors cause a person’s sleep propensity. The questionnaire is also self-administered, so scores are based on subjective reports.

A 2013 study looked at whether or not having the questionnaire administered by a physician instead of self-administering was more accurate in people with suspected obstructive sleep apnea.

The results showed the physician-administered scores to be more accurate. This suggests that having a doctor administer the questionnaire may make the ESS more reliable in predicting sleep apnea.

The ESS is not a diagnostic tool and can’t diagnose a sleep disorder. The questionnaire is meant to be used as a screening tool to help your doctor determine whether or not you need further testing, such as a referral for a sleep study.

There are other factors that can influence your results and cause your score to be higher, such as occasional insomnia.

If you’re worried about the quality of your sleep or concerned that you may have a sleep disorder, see your doctor regardless of what your self-assessment reveals.