Fatigue, sleep restriction and driving performance

1
Fatigue, sleep restriction and driving performance

• Professor Liu
• Student Ruby

2
Motive Purpose

• Motive---
• Fatigue and sleepiness are both factors to
  impair driving abilities but the cumulative
  effects of sleepiness on fatigue-related
  decrements performance have never been
  quantified.
• Purpose---
• The authors want to know the effects of fatigue
  alone or relative to sleepiness on performance.

3
References

• Fatigue
• Driving events which require sustained attention
  for long periods of time.
• (Lal and Craig,2001)
• After a period of rest can resolve fatigue.

4
References

• Sleepiness
• In the mid-afternoon, human generate a drop of
  vigilance.
• The end of the afternoon, human have a very
  alert period.
• (lavie,1986)
• After sleeping can resolve sleepiness.

5
Methods

• Subjects
• 22 healthy male.
• Sleep schedules
• Rested condition---
• 2100 to 0830 and go to bed from 2300 to
  0730
• Sleep restriction condition---
• 2100 to 0830 and go to bed from 2300 to 0100

6
Methods -Inclusion criteria

• Using actimeters to quantify sleep duration.
• This device can monitor body movements and
  calculate the mean night sleep events and the
  night awakenings.
• All subjects have tow driving periods, one is
  after normal sleep, and the other is after
  restricted sleep.

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Methods-Driving sessions

• Five sessions (200km each)
• The session times were 9001045, 11001245,
  13151500, 15151700 and 17151900.
• Speed at 130kph and not to cross the painted
  lines except to pass a slower car.
• Using the video camera filmed and recorded the
  road.

8
Methods-Driving sessions

• Before the testing and during each breaks,
  subjects were asked to rate their momentary
  fatigue (describe how fatigued you are now) and
  their sleepiness on the Karolinska Sleepiness
  Scale (KSS).
• Reaction time performances
• 10min simple reaction time test
• 176 black squares (2-7s)

9
Result-Actimetry
10
Result-Driving sessions

• In inappropriate line crossing (total)
• Usual sleep-66times
• Restricted sleep-535times

11
Result-reaction time performances

• Time of day and condition indicated a significant
  main effect.
• Time of day (F(5, 105) 4.868 p lt 0.01)
• Condition (F(1, 21) 20.447 p lt 0.001).
• The interaction between the two factors also
  significance
• (F(5, 105) 3.229 p lt 0.05).

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Result-Self-perception of fatigue and sleepiness

• Fatigue increased in the driving sessions
• Rested condition (fatigue score 24.7 (S.E.
  2.4) 2.1 (1.0) times session number from 1 to
  5 r 0.19 p 0.045).
• Sleep-restricted condition (fatigue score 49.5
  (3.9) 3.7 (1.2) times session number from 1 to
  5 r 0.28 p 0.0028).

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Result-Self-perception of fatigue and sleepiness

• Sleepiness increased insignificantly over the
  driving sessions in the rested condition (KSS
  2.7 (S.E. 0.3) 0.15 (0.09) times session
  number from 1 to 5 r 0.16 p 0.099).
• Significantly in the sleep-restricted condition
  (KSS 4.8 (0.45) 0.37 (0.13) times session
  number from 1 to 5 r 0.25 p 0.008).

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Result

• There was a significant association between the
  sleepiness on the Karolinska Sleepiness Scale and
  the line crossings (95 CI 1.181.66), which was
  related to an association in the sleep restricted
  condition (95 CI 1.42.4) but not in the rested
  condition (95 CI 0.81.3).

15
Discussion

• Even for short duration of driving (12 h) and
  normal time awake (8 h) sleep restriction can
  impair driving.
• Sleepiness also increased across the day after
  sleep deprivation.

16
Discussion

• Fatigue increase occurred in the sleep-restricted
  condition even before the first driving session,
  but there was no significant association of
  increasing fatigue with changing of driving
  performance.

17
Discussion

• Driving duration is not the main factor in
  driving impairment.
• Time awake in previous sleep duration have a much
  bigger impact.