How is the Epworth Sleepiness Scale (ESS) score calculated and what does it indicate about a patient's level of daytime sleepiness?

Epworth Sleepiness Scale (ESS) Score Calculation

The ESS is calculated by summing the patient's self-rated likelihood of dozing (0-3 scale) across eight specific daily situations, yielding a total score from 0 to 24, where scores ≥10 indicate excessive daytime sleepiness. 1, 2

How to Calculate the ESS Score

The patient rates their chance of dozing in each of eight situations using the following scale 1:

• 0 = would never doze
• 1 = slight chance of dozing
• 2 = moderate chance of dozing
• 3 = high chance of dozing

The Eight Situations Assessed

1. Sitting and reading
2. Watching TV
3. Sitting inactive in a public place (e.g., theater or meeting)
4. As a passenger in a car for an hour without a break
5. Lying down to rest in the afternoon when circumstances permit
6. Sitting and talking to someone
7. Sitting quietly after lunch without alcohol
8. In a car, while stopped for a few minutes in traffic

1, 2

The total ESS score is the sum of all eight ratings, ranging from 0 to 24. 2

Score Interpretation

• Scores <10: Normal range, not indicative of excessive daytime sleepiness 2
• Scores ≥10: Indicate excessive daytime sleepiness and warrant further evaluation 3, 2
• Scores ≥14: Predict a high likelihood of pathological sleepiness on objective testing (Multiple Sleep Latency Test) 4
• Scores >17: Considered high and insufficient alone to identify high-risk drivers, requiring direct clinical questioning 1

Clinical Validity and Limitations

The ESS correlates significantly with objective measures of sleepiness including sleep latency on the Multiple Sleep Latency Test (MSLT) and polysomnography, though the correlation is moderate (rho = -0.37) rather than strong. 2, 4

In patients with obstructive sleep apnea, ESS scores correlate with:

• Respiratory disturbance index 2
• Apnea-hypopnea index 5
• Minimum oxygen saturation overnight 2

Important Caveats

The ESS cannot confirm or exclude sleepiness on its own and should not be used as the sole determinant of driving risk or treatment decisions. 1 Self-reported sleepiness is subject to interpretation bias, and the ESS serves best as a screening prompt for direct clinical questioning rather than a diagnostic tool. 1

Physician-administered ESS scores are significantly higher and more accurate than self-administered scores (12.09 ± 4.1 vs 10.37 ± 5.49, p = 0.01), with better correlation to objective sleep study findings. 5 When patients self-administer the ESS, only 77% complete it properly compared to 100% when physician-administered. 5

Bed partners or living companions typically rate patients' sleepiness higher than patients rate themselves (mean score 11 vs 10, p < 0.001), though the two assessments are closely correlated (rho = 0.79). 6 This discrepancy suggests patients may underestimate their own sleepiness.

Clinical Application

The ESS is widely used in sleep medicine practice for:

• Initial screening of patients with suspected sleep disorders 1, 7
• Assessing daytime sleepiness in obstructive sleep apnea 1
• Monitoring treatment response 1
• Research outcome measurement 1

Every patient undergoing evaluation for sleep complaints should complete the ESS as part of the standard assessment battery, along with a two-week sleep diary and general medical/psychiatric questionnaire. 7