Fatigue, sleep restriction and driving performance Professor: Liu Student: Ruby

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.

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.

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.

Methods Subjects: 22 healthy male. Sleep schedules: Rested condition--- 21:00 to 08:30 and go to bed from 23:00 to 07:30 Sleep restriction condition--- 21:00 to 08:30 and go to bed from 23:00 to 01:00

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.

Methods-Driving sessions Five sessions (200km each) The session times were: 9:00–10:45, 11:00– 12:45, 13:15–15:00, 15:15–17:00 and 17:15– 19:00. 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.

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)

Result-Actimetry

Result-Driving sessions In inappropriate line crossing (total): Usual sleep-66times Restricted sleep-535times

Result-reaction time performances Time of day and condition indicated a significant main effect. Time of day (F(5, 105) = 4.868; p < 0.01) Condition (F(1, 21) = ; p < 0.001). The interaction between the two factors also significance (F(5, 105) = 3.229; p < 0.05).

Result-Self-perception of fatigue and sleepiness Fatigue increased in the driving sessions: Rested condition (fatigue score = 24.7 (S.E. = 2.4) (1.0) times session number from 1 to 5; r = 0.19; p = 0.045). Sleep-restricted condition (fatigue score = 49.5 (3.9) (1.2) times session number from 1 to 5; r = 0.28; p = ).

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) (0.09) times session number from 1 to 5; r = 0.16; p = 0.099). Significantly in the sleep-restricted condition (KSS = 4.8 (0.45) (0.13) times session number from 1 to 5; r = 0.25; p = 0.008).

Result There was a significant association between the sleepiness on the Karolinska Sleepiness Scale and the line crossings (95% CI: 1.18–1.66), which was related to an association in the sleep restricted condition (95% CI: 1.4–2.4) but not in the rested condition (95% CI: 0.8–1.3).

Discussion Even for short duration of driving (1–2 h) and normal time awake (8 h) sleep restriction can impair driving. Sleepiness also increased across the day after sleep deprivation.

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.

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