Article

Subjective sleepiness, simulated driving performance and blink duration: Examining individual differences. J Sleep Res 15: 47-53

National Institute for Psychosocial Medicine, Stockholm, Sweden.
Journal of Sleep Research (Impact Factor: 2.95). 03/2006; 15(1):47-53. DOI: 10.1111/j.1365-2869.2006.00504.x
Source: PubMed

ABSTRACT The present study aimed to provide subject-specific estimates of the relation between subjective sleepiness measured with the Karolinska Sleepiness Scale (KSS) and blink duration (BLINKD) and lane drifting calculated as the standard deviation of the lateral position (SDLAT) in a high-fidelity moving base driving simulator. Five male and five female shift workers were recruited to participate in a 2-h drive (08:00-10:00 hours) after a normal night sleep and after working a night shift. Subjective sleepiness was rated on the KSS in 5-min intervals during the drive, electro-occulogram (EOG) was measured continuously to calculate BLINKD, and SDLAT was collected from the simulator. A mixed model anova showed a significant (P < 0.001) effect of the KSS for both dependent variables. A test for a quadratic trend suggests a curvilinear effect with a steeper increase at high KSS levels for both SDLAT (P < 0.001) and BLINKD (P = 0.003). Large individual differences were observed for the intercept (P < 0.001), suggesting that subjects differed in their overall driving performance and blink duration independent of sleepiness levels. The results have implications for any application that needs prediction at the subject level (e.g. driver fatigue warning systems) as well as for research design and the interpretation of group average data.

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    • "It was concluded that there was always awareness of sleepiness before line crossings. In the previously mentioned simulator study (Ingre et al., 2006), the risk of line crossings with four wheels was increased 28 times at KSS = 8 and 185 times at KSS = 9, compared to the risk at KSS = 5. "
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    • "The frequency of blinks may increase or decrease as participants become more sleepy (Stern et al., 1984) and is consequently not useful for measuring sleepiness. In contrast, the duration of blinks has been found to increase in several studies (Caffier et al., 2003; Ingre et al., 2006; Schleicher et al., 2008). The increase is primarily due to a slower opening phase, but the closing phase increases as well (Lobb and Stern, 1986). "
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