Epworth Sleepiness Scale (ESS)

The ESS (Epworth Sleepiness Scale) is an 8-item self-report questionnaire that measures daytime sleepiness by rating the chance of dozing in everyday situations ^[1]. Scores above 10 indicate excessive daytime sleepiness that warrants evaluation for sleep apnea, narcolepsy, or hypersomnia.

The ESS is copyrighted by Dr. Murray Johns and licensed via Mapi Research Trust.

What does the ESS measure?

The Epworth Sleepiness Scale (ESS) was developed by Dr. Murray Johns at Epworth Hospital in Melbourne, Australia, and first published in Sleep in 1991. It measures an individual's general level of daytime sleepiness – also called somnolence, by asking them to rate, on a 0–3 scale, their chance of dozing in eight different everyday situations ranging from sitting quietly to driving in traffic.

Unlike actigraphy or polysomnography, the ESS captures the subjective propensity to fall asleep, a clinically meaningful dimension distinct from objective sleep duration. In the original study, ESS totals distinguished people with obstructive sleep apnea (OSA), narcolepsy and idiopathic hypersomnia from controls ^[1].

A total ESS score above 10 is the widely accepted threshold for excessive daytime sleepiness warranting further sleep evaluation. The score alone does not diagnose a sleep disorder: it is a screening tool that guides decisions about polysomnography (sleep study) or additional evaluation.

The ESS is copyrighted by Dr. Murray Johns, and a licence is required to use it whether or not a fee is payable. Licensing and translations are handled by Mapi Research Trust, and commercial use requires a licence (epworthsleepinessscale.com).

How do you give the ESS?

The ESS is a simple, self-administered questionnaire ^[1], typically completed in under five minutes with no clinician scoring or training required. Rate your chance of dozing in each situation using the 4-point scale below. Answer based on your usual recent lifestyle.

Rating scale

Each of the eight situations is rated for the chance of dozing on a 4-point scale: 0 = would never doze, 1 = slight chance, 2 = moderate chance, 3 = high chance.

How do you score and interpret the ESS?

Scores should be interpreted in the context of clinical history and examination.

Score interpretation

The ESS total ranges from 0 to 24 (eight items, each scored 0–3). A total of 10 or below falls in the normal range; a score above 10 indicates excessive daytime sleepiness that warrants further sleep evaluation ^[1]. The commonly applied severity gradation is:

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

Which sleep conditions raise the ESS score?

Elevated ESS scores are seen in obstructive sleep apnea, narcolepsy, idiopathic hypersomnia, and periodic limb movement disorder. In the original validation, ESS scores significantly distinguished these diagnostic groups from controls and correlated with objective sleep-latency measures, while the scores of people who only snored did not differ from controls ^[1].

Sleep assessment tools

The ESS is often paired with the Insomnia Severity Index (ISI) and the Pittsburgh Sleep Quality Index (PSQI) for a fuller sleep profile, and with the PHQ-9 to capture comorbid depression.

An ESS score above 10, especially with snoring, witnessed apneas, morning headaches, or non-restorative sleep, warrants referral to a sleep specialist or primary care evaluation for polysomnography. Do not drive or operate heavy machinery if you are experiencing excessive sleepiness. Untreated sleep apnea is associated with significantly elevated risk of motor vehicle accidents, cardiovascular disease, and metabolic syndrome.

Psychometric properties

• Original validation. In 180 adults (30 controls and 150 people with sleep disorders), ESS totals distinguished controls from people with obstructive sleep apnea syndrome, narcolepsy and idiopathic hypersomnia, and correlated with sleep latency on the multiple sleep latency test and overnight polysomnography ^[1].
• Reliability. In 87 healthy medical students retested 5 months apart, scores were stable (r = 0.82); internal consistency was high (Cronbach's α = 0.88), and factor analysis found a single factor in both students and people with sleep disorders ^[2].
• Sensitivity to treatment. Scores fell toward normal after 3–9 months of CPAP treatment in people with sleep apnea ^[2].
• Older men. In 3,059 older men (mean age 76.4), internal consistency was adequate (α = .70) and scores related to actigraphy, depressive symptoms and quality of life in expected directions ^[3].

Limitations

• Screening, not diagnosis. The ESS measures subjective sleepiness; it does not diagnose sleep apnea, narcolepsy or hypersomnia, which need polysomnography or a Multiple Sleep Latency Test.
• Snoring alone. In the original study, people who only snored did not differ from controls ^[1], so the ESS reflects daytime sleepiness, not snoring itself.
• Severity bands are convention. The >10 threshold is widely used; the mild, moderate and severe gradations are clinical convention rather than a single published guideline.
• Older adults. Internal consistency was lower in older men (α = .70), and the ESS distinguished reported sleep disorders less reliably than the PSQI ^[3].
• Self-report. Scores depend on the respondent's judgement of situations they may not encounter often.