ESS: Epworth Sleepiness Scale

What this assessment is

The Epworth Sleepiness Scale, or ESS, is an eight-item self-report measure of daytime sleepiness.

It asks how likely a person is to doze in common situations. The result describes a general tendency to fall asleep during the day, not how tired someone feels at one moment.

Murray Johns introduced the scale in a 1991 study. The standard adult version was revised in 1997.

The ESS measures sleepiness. It does not diagnose a sleep disorder.

That distinction matters.

Who it was designed for

The standard ESS is for adults. It has been studied in sleep clinics, community samples, and people with several medical and sleep conditions.

There are separate versions for children and adolescents. Translations and adapted forms also exist. They should be identified by their exact name and language.

Age, health, medication, work schedule, and sleep opportunity can affect a score. A result from a sleep-clinic patient is not directly comparable with every community result.

Use evidence from the same version and a similar population.

How it is administered

The respondent rates their usual chance of dozing in eight situations. Each response runs from 0, meaning no chance, to 3, meaning a high chance.

The developer's guidance describes the timeframe as recent life, usually the past few weeks or months. It is not a strict seven-day or 14-day recall period.

Answer every situation. If a situation has not occurred recently, the respondent estimates how it would usually affect them.

The person should complete the scale themselves when possible. A partner's observation is useful clinical context, but it is not a substitute for the standard self-report score.

What it measures

The ESS measures average daytime sleep propensity. In plain terms, it estimates how readily someone might doze during ordinary activities.

It does not directly measure sleep duration, sleep quality, insomnia symptoms, snoring, breathing pauses, or fatigue.

Those experiences can overlap without being the same.

The PSQI covers sleep quality and sleep disruption over the past month. STOP-Bang estimates risk for obstructive sleep apnea. The ESS focuses on daytime sleepiness.

Choose the measure that matches the question.

How scoring works

Score each of the eight responses from 0 to 3. Add them for a total from 0 to 24.

Higher totals indicate greater reported daytime sleepiness.

The official scoring guidance requires all eight responses. It does not support replacing a missing response with zero or estimating it from the other answers.

Do not prorate an incomplete form.

Check the version and the full 0-to-24 range before interpreting a result. A modified response scale produces a different measure.

How to interpret an ESS score

The developer's current adult guidance uses these ranges:

• 0 to 5: lower normal daytime sleepiness
• 6 to 10: higher normal daytime sleepiness
• 11 to 12: mild excessive daytime sleepiness
• 13 to 15: moderate excessive daytime sleepiness
• 16 to 24: severe excessive daytime sleepiness

These labels describe reported sleepiness. They are not diagnoses.

A higher result supports a closer review of sleep opportunity, medicines, substances, work schedule, health conditions, and possible sleep disorders. The pattern and its effect on daily life still matter.

If you are struggling to stay awake while driving, stop driving and seek medical advice. Do not use a questionnaire score to decide that driving is safe.

What the score cannot tell you

The ESS cannot identify the cause of sleepiness. It cannot show whether the cause is sleep apnea, narcolepsy, insufficient sleep, shift work, medication, depression, another illness, or more than one factor.

It also cannot rule out obstructive sleep apnea. Some people with sleep apnea do not report marked daytime sleepiness.

NICE guidance says not to use the ESS alone when deciding whether to refer someone with suspected sleep apnea.

Do not diagnose from the total.

Evidence and limitations

The original study found that ESS scores differed between diagnostic groups and were reasonably stable when repeated. Later research established the scale as a widely used measure of subjective daytime sleepiness.

Subjective is important.

It can miss risk.

The result depends on how a person understands the situations and recognizes their own dozing. It can disagree with laboratory measures, driving risk, or another person's observations.

The ESS also has a limited role in obstructive sleep apnea. Its score does not closely track apnea severity, and it should not replace a clinical history or sleep testing when those are needed.

Use the exact version, a complete response set, and the wider clinical picture.