Table 2

Tabular comparison of 200 cases and 199 controls in a case-control study of traffic crashes in Kittitas County, Washington, 1997–98. Controls matched to cases on place, time of day, and day of week. Some missing values in most categories

Trip characteristics
    Pavement condition
        Snow, slush, or ice6936.3126.1
    Any passenger10251.011457.3
    Child passenger, 0 to 12 years136.53517.6
    Adult passenger, 20 years or older8542.59749.0
Driver characteristics
    Driver age (years)
    Male driver13467.014170.9
        High school or less6633.05326.6
        Some college7537.55929.7
    Income in thousands of dollars
    Drank alcohol in last 8 hours84.084.0
    Crashes in last 5 years
    Using a cellular phone at crash or reference time23.477.5
Vehicle characteristics
    Large truck105.252.6
    Vehicle model year
Factors related to drowsiness
    Trip miles driven by driver
    Hours since trip started
    Hours since last sleep
    Hours of sleep in previous 48 hours
    Average hours slept per day in last week
    Average sleep hours needed per day
    Break taken on trip11758.511959.8
    Used highway rest stop2914.54422.1
    Nap during trip84.010.5
    Sensation of falling asleep on trip115.510.5
    Yawned while driving3418.45832.4
    Ate in last 2 hours6030.55125.8
    Radio, tape, or compact disk player on12563.114371.9
    Window open5527.85528.2
    In last 2 hours, drank
        Soda with caffeine5929.53618.2
        Any caffeinated beverage11055.011260.6
    Past crashes due to falling asleep115.542.0
    Ever fell asleep at the wheel8040.07839.2
    History of sleep apnea diagnosis31.531.5
    Snore most nights6936.38042.3
    Gasp in sleep2110.62412.2
    Epworth sleep score