What is the Epworth Sleepiness Scale?
In 1991, Murray W. Johns published a method in the journal Sleep for measuring daytime sleepiness based on asking people how likely they would be to fall asleep in a series of common, everyday situations. The instrument is brief, self-administered, and requires no equipment.
In 1999, Chiner and colleagues published in Archivos de Bronconeumología the validation of the Spanish version of the scale in patients with sleep apnea syndrome, which is the usual reference for its use in Spain.
The scale captures a subjective perception of sleep propensity under specific circumstances, not an objective measure of sleep quality or a physiological record. This nature limits what can and cannot be concluded from it.
What it measures and what it doesn’t measure
- It measures daytime sleepiness as perceived by the individual in everyday situations.
- It does not measure the quality or quantity of nighttime sleep, which require other methods.
- It does not diagnose sleep apnea, narcolepsy, or any other pathology: it is a screening tool that guides the need for further study.
- It does not assess psychosocial factors of work: it does not report on workload, autonomy, social support or organization of working time.
- It does not, by itself, determine suitability for a job nor justify a work limitation.
Why is it relevant in the workplace?
Excessive sleepiness is a factor that can impair attention, increase reaction time, and raise the likelihood of errors and incidents, especially while driving, operating machinery, monitoring processes, and performing monotonous tasks. The INSST (National Institute for Safety and Health at Work) highlights the effects of shift and night work on sleep and health in its documentation on these work arrangements.
That’s why the scale sometimes appears in the workplace. Its proper place is as one more tool within health surveillance, applied by healthcare personnel from the prevention service, and not as a questionnaire that the company distributes and uses on its own.
Conditions of use in prevention
- Healthcare setting. Its administration and interpretation correspond to the healthcare personnel of the prevention service.
- Voluntariness and confidentiality. The guarantees of Article 22 of Law 31/1995 apply: consent except for legally provided exceptions, respect for privacy and confidentiality of health information.
- Limited access. The company does not have access to the result, but only, if applicable, to the conclusions regarding suitability and the appropriate measures.
- Context. A high result points towards the study of sleep and towards the review of working conditions, not towards a decision about the person.
- Organizational complement. Preventive action is directed at the organization of shifts, breaks and task design, not just at the person.
How to interpret
The scale produces an overall score that is interpreted as an estimate of the degree of perceived daytime sleepiness. The cut-off points are taken from the clinical literature and vary depending on the population studied and the purpose of the screening; therefore, they should be applied with professional judgment and not as universal thresholds.
A high score indicates a pronounced tendency to sleep that warrants investigation; however, it does not pinpoint a cause. It may be due to a sleep disorder, sleep deprivation caused by work schedules or family responsibilities, the effects of medication, or the organization of work itself. Distinguishing between these causes requires medical evaluation and, often, additional tests.
The instrument should not be used to compare people or to build template indicators, because its basis is subjective and its purpose is individual and clinical.
Limitations and common errors
- Presenting it as a method for evaluating psychosocial risks, for which it is not designed.
- Using it as an aptitude test or as a criterion for restricting access to a position.
- Apply it outside the healthcare field or disseminate its results within the company.
- Interpreting the score as a diagnosis of sleep apnea or other pathology.
- Extrapolating cut-off points from one population to another without justification.
- Focusing only on the individual result and not reviewing the organization of working time that may be causing it.
Practical example
A transport company with rotating shifts detects an increase in minor traffic incidents on the night shift and requests a health surveillance review from the prevention service.
- Scope. Healthcare personnel incorporate drowsiness screening into medical examinations, informing patients of its purpose and with guarantees of confidentiality.
- Result: Several people presented high scores. In two cases, a sleep study was conducted, and in others, the cause pointed to the rotation and duration of the commutes.
- Measures. The direction and speed of shift rotation are reviewed, scheduled breaks are introduced, and start times are adjusted.
- Follow-up. The company receives fitness conclusions and organizational recommendations, without access to individual health data.
Differences with other instruments
- Compared to FPSICO and CoPsoQ-istas21. These evaluate psychosocial factors of work organization; Epworth measures an individual perception of sleepiness.
- Compared to polysomnography. This is an objective sleep recording test; the scale is a screening questionnaire.
- Regarding fatigue questionnaires: Fatigue and sleepiness are related but distinct phenomena, each with its own instruments.
- Regarding the aptitude test: Aptitude is determined using specific protocols by healthcare personnel, not with an isolated screening tool.
Regulatory and technical framework
- Law 31/1995, article 22. Health surveillance: voluntariness, confidentiality and limited access to health information.
- Royal Decree 1561/1995 . Special working days, with rules on night work and shifts.
- INSST fact sheet on shift work . Effects on sleep and organizational criteria.
- NTP 502 of the INSST . Criteria for the analysis of shift work.
No Spanish regulation provides for the use of this scale. Its use, when appropriate, falls within the framework of health surveillance and is decided by the healthcare personnel of the prevention service.
