Table 2.

Prediction Accuracy for Subjective Ratings for the Occurrence of Severe/Moderate Drowsy Driving Events in the Next 15 Minutes

Item	Description	OR [95% CI]β	p	AUC [95% CI]	p
Severe driving event: emergency brake
KSS	Subjective sleepiness	2.40 [1.18, 4.91]	0.016	0.90 [0.84, 0.96]	0.001
LFA	Likelihood of falling asleep	2.10 [1.21,3.67]	0.009	0.85 [0.77, 0.92]	0004
SSQ1	Struggle to keep eyes open	2.21 [1.35, 3.62]	0.002	0.91 [0.84, 0.98]	0.001
SSQ2	Vision blurred	2.15 [1.38, 3.36]	0.001	0.91 [0.86, 0.97]	<0.001
SSQ3	Nodding off to sleep	1.76 [1.21, 2.56]	0.003	0.87 [0.80, 0.95]	0.002
SSQ4	Difficulty keeping to middle of road	2.21 [1.39, 3.53]	0.001	0.88 [0.74, 1.00]	0.002
SSQ5	Difficulty maintaining correct speed	1.98 [1.27, 3.10]	0.001	0.81 [0.59, 1.00]	0.009
SSQ6	Mind wandering	2.29 [1.31, 4.01]	0.004	0.86 [0.71, 1.00]	0.002
SSQ7	Reactions are slow	1.79 [1.20, 2.68]	0.004	0.85 [0.75, 0.96]	0.003
SSQ8	Head dropping	—	n.s.	—	n.s.
SSQ global score		1.09 [1.04, 1.16]	0.001	0.88 [0.78, 0.98]	0.002
Moderate driving event: lane deviation
KSS	Subjective sleepiness	1.22 [1.09, 1.36]	<0.001	0.65 [0.57, 0.73]	<0.001
LFA	Likelihood of falling asleep	—	n.s.	—	n.s.
SSQ1	Struggle to keep eyes open	1.17 [1.01, 1.36]	0.039	0.60 [0.51, 0.68]	0.025
SSQ2	Vision blurred	1.24 [1.05, 1.47]	0.013	0.60 [0.51, 0.68]	0.024
SSQ3	Nodding off to sleep	1.21 [1.02, 1.43]	0.029	0.59 [0.51, 0.67]	0.032
SSQ4	Difficulty keeping to middle of road	1.22 [1.02, 1.45]	—	—	n.s.
SSQ5	Difficulty maintaining correct speed	—	—	—	n.s.
SSQ6	Mind wandering	—	—	—	n.s.
SSQ7	Reactions are slow	—	—	—	n.s.
SSQ8	Head dropping	—	—	—	n.s.
SSQ global score		—	n.s.	—	n.s.

Continuous OR—change in odds of a severe/moderate event occurring in the next 15 minutes with each point increase on the predictor scale.