Karolinska, Stanford, Epworth: three sleepiness scales and what each one can answer

The three standard sleepiness scales answer different questions. The Karolinska Sleepiness Scale and the Stanford Sleepiness Scale rate how sleepy a person is at the moment of asking. The Epworth Sleepiness Scale estimates how likely a person is to doze off in eight everyday situations across recent weeks. A 6 on one has no equivalent on the others, and the Epworth’s published cutoffs differ by source.

The Karolinska scale: nine steps, asked often

Torbjörn Åkerstedt and Mats Gillberg at the Karolinska Institute devised it in 1990, and it has been used mostly in sleep, shift-work and fatigue research. The respondent picks one of nine labels, from 1 (“extremely alert”) through 5 (“neither alert nor sleepy”) to 9 (“very sleepy, great effort to keep awake, fighting sleep”). The steps in between include 7, “sleepy but no effort to keep awake,” and 8, “sleepy and some effort to keep awake.”

It was built to be repeated, hourly or more often, and scores climb the longer someone stays awake and move with time of day. Kaida and colleagues (2006) checked it against performance and EEG measures and found that ratings tracked both. A 2016 comparison (Miley et al.) found that a version with every point labeled and one with alternate points labeled give nearly the same results. The site’s piece on sleep inertia uses the scale to describe how sleepy waking feels.

The Stanford scale: seven statements, one moment

E. Hoddes, V. Zarcone, H. Smythe, R. Phillips and William Dement published it in Psychophysiology in 1973. The respondent chooses one of seven statements, running from feeling active and alert to almost asleep and losing the struggle to stay awake. The wording varies between reproductions, so any copy you find may not match another.

Murray Johns, in the 1991 paper that introduced the Epworth scale, criticized it, and its visual-analogue cousins, as measuring “feelings of sleepiness at a particular time” instead of a general level. He added that the subjective sleepiness they capture is not the same as the objective sleepiness measured by the multiple sleep latency test, a lab nap procedure. The same limit of asking about a moment applies to the Karolinska scale, although the validation work above tested it against performance and EEG.

The Epworth scale: eight situations, recent weeks

Johns, at Epworth Hospital in Melbourne, published it in Sleep in 1991. The eight situations include sitting and reading, watching TV, being a passenger in a car for an hour without a break, and sitting quietly after lunch without alcohol. The respondent rates the chance of dozing in each from 0 (“would never doze”) to 3 (“high chance of dozing”), thinking of the “usual way of life in recent times,” and the total runs from 0 to 24. If a situation hasn’t come up lately, the respondent works out how it would have affected them.

His first sample was 180 adults. The 30 normal controls averaged 5.9 (range 2 to 10). Sleep apnea patients averaged 11.7, narcolepsy 17.5 and idiopathic hypersomnia 17.9. Scores of 16 or more turned up only among patients with moderate or severe sleep apnea, narcolepsy or idiopathic hypersomnia.

Side by side

	Karolinska	Stanford	Epworth
Year	1990	1973	1991
Range	1 to 9	1 to 7	0 to 24
Asks about	This moment	This moment	Recent weeks
Format	Pick one label	Pick one statement	Rate 8 situations, add up
Built for	Repeated checks, shift work	Repeated checks, lab work	One-off screening, clinics
Checked against	EEG and performance	Self-report only; Johns (1991) says it differs from nap-test sleepiness	Nap latency, overnight studies

Why the Epworth cutoff depends on where you look

Johns’s paper does not hand down bands. Its closest thing to a line is the control range, which topped out at 10, hence the “ESS > 10” wording used when comparing patients with controls. Handouts and clinic websites have since made their own. One patient handout (Carepatron’s) calls 0 to 10 normal, 11 to 12 mild, 13 to 15 moderate and 16 to 24 severe. University of Michigan Health’s page reads 0 to 7 as unlikely to be abnormally sleepy, 8 to 9 as average, 10 to 15 as possibly excessive and 16 to 24 as excessive. One encyclopedia entry calls 0 to 9 normal and advises medical advice from 10. These were the pages as found while researching this post, and they may change. A score of 10 is therefore “normal” on one sheet and “possibly excessive” on another.

If you score yourself, write down which sheet you used. If a clinician scores you, ask which bands they apply.

Choosing between them

For a question about the last few weeks, such as whether afternoons have been dragging, the Epworth scale is the clinical standard, and a high score is a reason to see someone. The Stanford scale is the oldest of the three and the least suited to this kind of decision, since its wording varies between versions. One result from Johns’s first sample argues against reading any of these as a sleep-quality score: the lowest average belonged to patients with insomnia.

For a check on the next hour, such as before a long drive or a late shift, the Karolinska scale is the one built for repetition, with validation against performance and EEG behind it. No source reviewed here sets a rating above which driving is unsafe for an individual, and a self-rating can be wrong in the dangerous direction, so the number is a prompt to stop, not permission to continue.