Clinical Definition

The Epworth Sleepiness Scale (ESS) is a subjective scale that assesses the general level of daytime sleepiness, or the propensity to fall asleep during common, sedentary situations. The questionnaire consists of eight items, each scored on a 4-point scale from 0 (would never doze) to 3 (high chance of dozing). The total score ranges from 0 to 24.

It is one of the most widely used tools in sleep medicine for screening for excessive daytime sleepiness (EDS) and for monitoring treatment response.

Etymology & History

The scale was developed by Dr. Murray Johns in Melbourne, Australia, and first published in 1991. It was named after the Epworth Hospital where he worked. Its simplicity and validity have made it a global standard.

Reference Values & Interpretation

Normal Values

A score of 0-10 is considered to be within the normal range for healthy adults.

Abnormal Values

A score of 11-15 indicates mild to moderate daytime sleepiness. A score of 16 or higher indicates severe daytime sleepiness and is a strong indicator of a clinically significant sleep disorder requiring further evaluation.

How It's Measured

The ESS is a self-administered questionnaire. The patient rates their likelihood of dozing in eight situations:

  • Sitting and reading
  • Watching TV
  • Sitting inactive in a public place
  • As a passenger in a car for an hour without a break
  • Lying down to rest in the afternoon
  • Sitting and talking to someone
  • Sitting quietly after lunch without alcohol
  • In a car, while stopped for a few minutes in traffic

The scores for each situation are summed to get the total.

Role in Diagnosis

A high ESS score (≥11) is not diagnostic of a specific disorder but is a strong indication that a significant sleep problem may be present. It is a critical part of the initial clinical evaluation for sleep apnea, narcolepsy, and idiopathic hypersomnia.

Role in Treatment

A primary goal of treatment for sleep disorders like OSA is to reduce daytime sleepiness. A decrease in the ESS score is a key indicator of successful treatment. Clinicians will often administer the ESS before and after treatment to objectively measure the improvement in a patient's quality of life and daytime function.

Associated Conditions

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Clinical Guidelines

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Latest Research & Updates

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While widely used, the ESS has limitations. It is subjective and can be influenced by mood disorders like depression. It measures sleep propensity in sedentary situations and may not capture sleepiness during active tasks. Despite this, it remains a valuable and efficient clinical tool.