Evidence of drowsiness

Subjective sleepiness - Objective drowsiness

Subjective sleepiness

Notion of drowsiness complaint

This sleepiness can be quantified subjectively by means of questionnaires (Epworth or Stanford sleepiness scale).

Epworth scale

How likely is it that you will fall asleep - not just feel tired - under the following conditions? Think about how you normally live. Even if you have not recently found yourself in such circumstances, imagine your reaction.

Use the scale below to choose the most appropriate number for each situation.

  • 0 = no risk of falling asleep
  • 1 = slight chance of falling asleep
  • 2 = moderate possibility of falling asleep
  • 3 = high chance of falling asleep
Situation Chances of falling asleep
  •  0
  •  1
  •  2
  •  3
Sitting and reading
Watching television
Sitting idle in public (e.g. at the theatre)
or at a meeting)
As a passenger in a car for an hour
Lying down for an afternoon nap
if circumstances permit
Sitting and talking with someone
Sitting quietly after a meal
without alcohol
At the wheel, after a few minutes of stopping
during a traffic jam

Objective drowsiness

A complaint of sleepiness should be assessed objectively by performing an iterative sleep latency test (ISLT). This test requires the simultaneous recording of the electroencephalogram (EEG), electromyogram (EMG) and electro-occulogram (EOG).

The instructions for the test are as follows: the patient lies down in the dark with 5 sessions of 20 minutes each during the day, every 2 hours and 2 hours after waking up in the morning.
A prior polysomnographic recording is essential for the interpretation of the TILE. For a recording from 11pm to 7am, the tests will be performed at 9am, 11am, 1pm, 3pm and 5pm.

The sleep latency during each test is then calculated and the average sleep latency over all tests is calculated.
The interpretation will also take into account the number of REM sleep episodes, characterised by the occurrence of this stage in less than 15 minutes.

A mean latency to sleep on the TILE of less than 8 minutes indicates pathological daytime sleepiness, more than 10 minutes indicates no sleepiness, and between these values pathological character must take into account the clinical context.