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
| Cases | Controls | |||
|---|---|---|---|---|
| Characteristic | No | % | No | % |
| Trip characteristics | ||||
| Pavement condition | ||||
| Dry | 99 | 52.1 | 154 | 78.6 |
| Wet | 22 | 11.6 | 30 | 15.3 |
| Snow, slush, or ice | 69 | 36.3 | 12 | 6.1 |
| Any passenger | 102 | 51.0 | 114 | 57.3 |
| Child passenger, 0 to 12 years | 13 | 6.5 | 35 | 17.6 |
| Adult passenger, 20 years or older | 85 | 42.5 | 97 | 49.0 |
| Driver characteristics | ||||
| Driver age (years) | ||||
| 18–29 | 74 | 37.0 | 36 | 18.1 |
| 30–44 | 51 | 25.5 | 70 | 35.2 |
| 45–64 | 50 | 25.0 | 78 | 39.2 |
| ≥65 | 25 | 12.5 | 15 | 7.5 |
| Male driver | 134 | 67.0 | 141 | 70.9 |
| Education | ||||
| High school or less | 66 | 33.0 | 53 | 26.6 |
| Some college | 75 | 37.5 | 59 | 29.7 |
| College | 59 | 29.5 | 87 | 43.7 |
| Income in thousands of dollars | ||||
| <25 | 69 | 36.3 | 39 | 20.0 |
| 25–74 | 95 | 50.0 | 112 | 57.4 |
| ≥75 | 26 | 13.7 | 44 | 22.6 |
| Drank alcohol in last 8 hours | 8 | 4.0 | 8 | 4.0 |
| Crashes in last 5 years | ||||
| 0 | 131 | 65.5 | 154 | 77.8 |
| 1 | 52 | 25.5 | 36 | 18.2 |
| ≥2 | 18 | 9.0 | 8 | 4.0 |
| Using a cellular phone at crash or reference time | 2 | 3.4 | 7 | 7.5 |
| Vehicle characteristics | ||||
| Car | 148 | 76.7 | 152 | 80.0 |
| Pick-up | 35 | 18.1 | 33 | 17.4 |
| Large truck | 10 | 5.2 | 5 | 2.6 |
| Vehicle model year | ||||
| <1990 | 77 | 39.9 | 59 | 31.2 |
| 1990–93 | 57 | 29.5 | 64 | 33.9 |
| 1994–98 | 59 | 30.6 | 66 | 34.9 |
| Factors related to drowsiness | ||||
| Trip miles driven by driver | ||||
| <100 | 106 | 54.9 | 109 | 56.8 |
| 100–199 | 57 | 29.5 | 62 | 32.3 |
| ≥200 | 30 | 15.5 | 21 | 10.9 |
| Hours since trip started | ||||
| <4 | 162 | 81.0 | 155 | 77.9 |
| 4–7 | 27 | 13.5 | 29 | 14.0 |
| ≥8 | 11 | 5.5 | 15 | 7.5 |
| Hours since last sleep | ||||
| <6 | 94 | 47.0 | 85 | 42.7 |
| 6–11 | 81 | 40.5 | 73 | 36.7 |
| 12–17 | 21 | 10.5 | 39 | 19.6 |
| ≥18 | 4 | 2.0 | 2 | 1.0 |
| Hours of sleep in previous 48 hours | ||||
| <12 | 16 | 9.2 | 10 | 5.5 |
| 12–17 | 106 | 60.9 | 136 | 74.7 |
| ≥18 | 52 | 29.9 | 36 | 19.8 |
| Average hours slept per day in last week | ||||
| <7 | 31 | 15.5 | 35 | 17.7 |
| 7–8 | 136 | 68.0 | 142 | 71.7 |
| ≥9 | 33 | 16.5 | 21 | 10.6 |
| Average sleep hours needed per day | ||||
| <7 | 25 | 12.6 | 23 | 11.6 |
| 7–8 | 138 | 69.7 | 151 | 76.3 |
| ≥9 | 35 | 17.7 | 24 | 12.1 |
| Break taken on trip | 117 | 58.5 | 119 | 59.8 |
| Used highway rest stop | 29 | 14.5 | 44 | 22.1 |
| Nap during trip | 8 | 4.0 | 1 | 0.5 |
| Sensation of falling asleep on trip | 11 | 5.5 | 1 | 0.5 |
| Yawned while driving | 34 | 18.4 | 58 | 32.4 |
| Ate in last 2 hours | 60 | 30.5 | 51 | 25.8 |
| Radio, tape, or compact disk player on | 125 | 63.1 | 143 | 71.9 |
| Window open | 55 | 27.8 | 55 | 28.2 |
| In last 2 hours, drank | ||||
| Coffee | 52 | 26.0 | 81 | 40.9 |
| Tea | 4 | 2.0 | 7 | 3.5 |
| Soda with caffeine | 59 | 29.5 | 36 | 18.2 |
| Any caffeinated beverage | 110 | 55.0 | 112 | 60.6 |
| Past crashes due to falling asleep | 11 | 5.5 | 4 | 2.0 |
| Ever fell asleep at the wheel | 80 | 40.0 | 78 | 39.2 |
| History of sleep apnea diagnosis | 3 | 1.5 | 3 | 1.5 |
| Snore most nights | 69 | 36.3 | 80 | 42.3 |
| Gasp in sleep | 21 | 10.6 | 24 | 12.2 |
| Epworth sleep score | ||||
| <5 | 40 | 21.7 | 45 | 24.1 |
| 5–7 | 53 | 28.8 | 58 | 31.0 |
| 8–10 | 50 | 27.2 | 42 | 22.5 |
| 11–22 | 41 | 22.3 | 42 | 22.5 |