Epworth Sleepiness Scale (ESS)
Table of Contents
Epworth Sleepiness Scale (ESS): Measure Your Daytime Sleepiness
The Epworth Sleepiness Scale (ESS) is a widely used self-assessment tool designed to measure your general level of daytime sleepiness. Developed by Dr. Murray Johns in 1991, the ESS helps identify excessive daytime sleepiness, a symptom commonly associated with sleep disorders such as insomnia, sleep apnea, narcolepsy, and more.
What Does the ESS Assess?
The ESS evaluates how likely you are to doze off or fall asleep in eight common situations, each reflecting routine daily activities. By assessing your likelihood of dozing off in these situations, the ESS quantifies your daytime sleepiness and helps determine if further evaluation or treatment might be beneficial.
How Does the ESS Work?
The ESS consists of eight scenarios where you rate your chance of falling asleep or dozing off on a scale from 0 to 3:
0: Would never doze
1: Slight chance of dozing
2: Moderate chance of dozing
3: High chance of dozing
The scenarios include situations such as sitting and reading, watching TV, or riding as a passenger in a car.
Scoring the Epworth Sleepiness Scale
Your ESS score is calculated by summing your responses for each of the eight scenarios. Total scores range from 0 to 24, with higher scores indicating greater daytime sleepiness.
Score Interpretation:
0–7: Normal daytime sleepiness
8–9: Mild sleepiness
10–15: Moderate sleepiness (suggests possible clinical significance)
16–24: Severe daytime sleepiness (requires medical evaluation)
When Should You Use the ESS?
The ESS is particularly valuable if you’re experiencing persistent fatigue, sleepiness, or difficulty staying awake during the day, which can significantly impact your daily functioning. Healthcare providers often use ESS scores alongside other assessments to diagnose sleep disorders and guide treatment plans.
Take the Epworth Sleepiness Scale Test
Interpreting ESS Scores
After calculating the ESS total score, clinicians interpret the result to gauge the severity of a person’s daytime sleepiness. In general, higher scores mean greater levels of EDS (Excessive Daytime Sleepiness). The following score ranges are commonly used as a guide to interpretation:
- 0–10: Normal sleepiness. This range is considered within the normal level for healthy adults, indicating no significant daytime sleepiness. Most people without sleep disorders score in the single digits on the ESS. In fact, epidemiological studies have found that the reference “normal” ESS score in adults is around 4–6 on average, and virtually all healthy individuals score 10 or below.
- 11–14: Mild excessive sleepiness. Scores in this range suggest a mild elevation in daytime sleepiness beyond the normal level. A person with an ESS of 11–14 may notice they doze off slightly more easily than average. While not severely sleepy, this result can be a warning sign of possible sleep issues. In clinical practice, an ESS ≥11 is often considered abnormal and may warrant further investigation.
- 15–17: Moderate excessive sleepiness. Scores in the mid-to-upper teens indicate moderate EDS. People in this range have a marked tendency to fall asleep during the day. Such a result strongly suggests the presence of a sleep disorder or insufficient sleep that is significant enough to impair daytime alertness. It would be advisable for individuals with ESS scores in the mid-teens to undergo a comprehensive sleep evaluation.
- 18–24: Severe excessive sleepiness. Scores in this highest range signify severe daytime sleepiness. An ESS in the high teens or twenties is very elevated; these individuals have difficulty staying awake in many passive situations and are at risk of falling asleep even during activities that require some attention. Severe ESS scores (≥18) are often seen in conditions like untreated obstructive sleep apnea or narcolepsy. Indeed, almost all patients suffering from narcolepsy have ESS scores in the moderate-to-severe range. A score this high is a strong indication that immediate medical follow-up is needed, as it can impair daily functioning and safety (for instance, high ESS scores correlate with higher risk of accidents due to microsleep episodes).
It’s worth noting that different sources sometimes use slightly different cut-offs or descriptors for these ranges. The overarching idea, however, is that an ESS total above 10 falls outside the normal range and signals excessive sleepiness. Clinicians use these thresholds as rough guidelines rather than absolute criteria, considering the patient’s overall context. For example, an ESS of 16 in a patient with loud snoring and observed apneas would strongly point toward obstructive sleep apnea, whereas an ESS of 12 in an otherwise healthy person might prompt looking for subtler issues (like mild sleep deprivation or an emerging sleep disorder). In summary, the ESS score interpretation helps stratify patients by their sleepiness level: normal vs. mildly, moderately, or severely sleepy, which in turn guides the urgency and type of further evaluation.
Reliability and Validity of the Epworth Sleepiness Scale
The effectiveness of the Epworth Sleepiness Scale (ESS) hinges on two critical psychometric properties: reliability and validity. Understanding these properties ensures that the ESS provides consistent and accurate assessments of sleepiness.
Reliability of the ESS
Reliability refers to the consistency of a measurement tool—whether it yields the same results under consistent conditions. For the ESS, reliability is evaluated through two main aspects:
Test-Retest Reliability: This assesses whether the ESS produces similar scores when administered to the same individual on different occasions, assuming no significant change in their sleepiness levels.
In Healthy Individuals: A study involving 87 healthy medical students found that their ESS scores remained stable over a 5-month period, with a high correlation coefficient of 0.82. This indicates strong test-retest reliability in non-clinical populations.
In Clinical Populations: However, in clinical settings—such as among patients with sleep disorders—the ESS has shown greater variability. For instance, research involving patients with suspected obstructive sleep apnea (OSA) reported higher test-retest variability, with discrepancies in scores of 5 points or more observed in up to 42% of cases over intervals ranging from 11 to 91 days. This suggests that while the ESS is reliable in healthy individuals, its consistency may diminish in clinical populations, potentially due to fluctuations in sleep patterns or other health-related factors.
Internal Consistency: This evaluates whether the items within the ESS measure the same underlying concept of sleepiness.
- The ESS has demonstrated high internal consistency, with a Cronbach’s alpha coefficient of 0.88. This indicates that the eight items of the ESS are cohesively measuring the same construct of daytime sleepiness.
Validity of the ESS
Validity refers to the extent to which a tool measures what it is intended to measure. For the ESS, validity encompasses several dimensions:
Construct Validity: This determines whether the ESS accurately measures the concept of daytime sleepiness.
- Factor analysis studies have consistently shown that the ESS assesses a single underlying factor, confirming its unidimensionality. This means that all eight items on the ESS are effectively evaluating the same aspect of sleepiness.
Criterion Validity: This examines how well the ESS scores correlate with other established measures of sleepiness.
- The ESS has shown a significant association with self-rated problem sleepiness but exhibits a moderate correlation (r = 0.51) with objective measures like the Multiple Sleep Latency Test (MSLT), which assesses the time it takes to fall asleep in a quiet environment during the day. This suggests that while the ESS is effective in capturing subjective sleepiness, it may not fully align with objective sleepiness assessments.
Discriminant Validity: This assesses the ESS’s ability to distinguish between different groups based on their sleepiness levels.
- Studies have demonstrated that the ESS can effectively differentiate between individuals with and without sleep disorders. For example, patients with conditions like OSA, narcolepsy, and idiopathic hypersomnia tend to have higher ESS scores compared to healthy individuals, indicating the scale’s effectiveness in identifying excessive daytime sleepiness associated with these disorders.
Considerations and Limitations
While the ESS is a valuable tool for assessing daytime sleepiness, it’s essential to consider certain limitations:
Subjectivity: As a self-reported measure, the ESS relies on individuals’ perceptions of their sleepiness, which can be influenced by personal biases or lack of awareness.
Variability in Clinical Settings: The increased test-retest variability observed in clinical populations suggests that factors such as fluctuating sleep patterns, treatment interventions, or health status changes can affect ESS scores over time.
Cultural and Linguistic Adaptations: The ESS has been translated into multiple languages and adapted for various cultures. Ensuring the translated versions maintain the original’s reliability and validity is crucial for accurate assessments across different populations.
In conclusion, the Epworth Sleepiness Scale is a reliable and valid instrument for assessing daytime sleepiness, particularly in healthy individuals. Its ease of use and strong psychometric properties make it a valuable tool in both clinical and research settings. However, when interpreting ESS scores, especially in clinical populations, it’s important to consider potential variability and the subjective nature of self-reported measures.
Frequently Asked Questions (FAQ)
Can the ESS diagnose sleep disorders?
The ESS alone does not diagnose specific sleep disorders but indicates the presence and severity of daytime sleepiness, prompting further medical evaluation if necessary.
How often should I take the ESS?
You can retake the ESS periodically, especially if you notice changes in your sleep patterns or daytime alertness.
What should I do if my ESS score is high?
A high ESS score suggests excessive daytime sleepiness that may require professional assessment. Consider consulting a healthcare provider or sleep specialist for further evaluation and management.
Can I use the ESS to track changes over time?
Yes, the ESS is valuable for tracking changes in your daytime sleepiness levels, particularly during or after treatment for sleep-related issues.
Next Steps
If your ESS score suggests moderate to severe daytime sleepiness, consider speaking with a clinical psychologist or sleep specialist for a comprehensive assessment and treatment options.
Explore More Insomnia and Sleep Tools
Investigate other validated measures to assess insomnia, sleep quality, sleep hygiene, and factors like daytime sleepiness or beliefs about sleep. Track patterns with our sleep diary or visit our assessment hub for a full overview of insomnia assessment.
- Insomnia Severity Index (ISI) – Gold standard self-report tool for insomnia severity over two weeks.
- Pittsburgh Sleep Quality Index (PSQI) – Assesses overall sleep quality and disturbances over a month.
- Athens Insomnia Scale (AIS) – Broad sleep quality, not just insomnia.
- Sleep Condition Indicator (SCI) – Screens insomnia per DSM-5 with a focus on sleep satisfaction.
- Epworth Sleepiness Scale (ESS) – Guages daytime sleepiness across eight everyday situations.
- Sleep Hygiene Index (SHI) – Identifies sleep-disruptive habits and behaviours affecting rest.
- Dysfunctional Beliefs and Attitudes about Sleep (DBAS-16) – Probes unhelpful beliefs influencing sleep difficulties.
- Pre-Sleep Arousal Scale (PSAS) – Measures cognitive and physical arousal before bedtime.
- Assessment Hub: Central hub for all sleep and insomnia measures.
- Sleep Diary: Records daily sleep habits for personalised insights.
References for the Epworth Sleepiness Scale (ESS)
Chervin, R. D., Aldrich, M. S., Pickett, R., & Guilleminault, C. (1997). Comparison of the results of the Epworth Sleepiness Scale and the Multiple Sleep Latency Test. Journal of Psychosomatic Research, 42(2), 145–155. https://doi.org/10.1016/S0022-3999(96)00239-5
- This study compares ESS scores with results from the Multiple Sleep Latency Test, assessing the scale’s effectiveness in measuring daytime sleepiness.
Johns, M. W. (1991). A new method for measuring daytime sleepiness: the Epworth Sleepiness Scale. Sleep, 14(6), 540–545. https://doi.org/10.1093/sleep/14.6.540
- This foundational article introduces the ESS as a new method for measuring daytime sleepiness, detailing its development and initial validation.
Johns, M. W. (1992). Reliability and factor analysis of the Epworth Sleepiness Scale. Sleep, 15(4), 376–381. https://pubmed.ncbi.nlm.nih.gov/1519015/
- This study examines the reliability and internal consistency of the ESS, demonstrating its stability over time and its effectiveness in measuring daytime sleepiness.
Johns, M. W. (1993). Daytime sleepiness, snoring, and obstructive sleep apnea: the Epworth Sleepiness Scale. Chest, 103(1), 30–36. https://doi.org/10.1378/chest.103.1.30
- This study explores the relationship between ESS scores, snoring, and obstructive sleep apnea, highlighting the scale’s utility in identifying sleep-related breathing disorders.
Kendzerska, T. B., Smith, P. M., Brignardello-Petersen, R., Leung, R. S., & Tomlinson, G. A. (2014). Evaluation of the measurement properties of the Epworth Sleepiness Scale: a systematic review. Sleep Medicine Reviews, 18(4), 321–331. https://doi.org/10.1016/j.smrv.2013.08.002
- This systematic review evaluates the measurement properties of the ESS, summarizing evidence on its reliability, validity, and responsiveness across various populations.
Olson, L. G., Cole, M. F., & Ambrogetti, A. (1998). Correlations among Epworth Sleepiness Scale scores, Multiple Sleep Latency Tests, and psychological symptoms. Journal of Sleep Research, 7(4), 248–253. https://doi.org/10.1046/j.1365-2869.1998.00123.x
- This research explores the relationships between ESS scores, Multiple Sleep Latency Test results, and psychological symptoms, providing a comprehensive view of sleepiness assessment.
