Table 2. Hierarchical Negative Binomial Model for County MVC Mortality.
| Parameter | Mortality Rate Ratio (95% CI) | P Value |
|---|---|---|
| County EMS Response Time | ||
| Median EMS response time, min | ||
| <7 | 1 [Reference] | <.001 |
| 7-8 | 1.24 (1.15-1.34) | |
| 9-11 | 1.33 (1.23-1.44) | |
| ≥12 | 1.46 (1.32-1.61) | |
| Population Demographic Group | ||
| Male sex | 1.59 (1.52-1.6) | <.001 |
| Age, y | ||
| <15 | 1 [Reference] | <.001 |
| 15-34 | 7.39 (6.88-7.94) | |
| 35-64 | 4.39 (4.08-4.71) | |
| ≥65 | 5.71 (5.31-6.14) | |
| County Rurality | ||
| Rural-urban continuum | ||
| Urban | 1 [Reference] | .002 |
| Suburban | 1.03 (0.94-1.13) | |
| Rural | 1.18 (1.09-1.27) | |
| Wilderness | 1.26 (1.14-1.40) | |
| Population density, people/mile2 | ||
| <16 | 1.90 (1.66-2.18) | <.001 |
| 17-42 | 1.46 (1.32-1.62) | |
| 43-108 | 1.34 (1.23-1.45) | |
| ≥109 | 1 [Reference] | |
| EMS Time Intervals | ||
| On-scene time (per 2-min increase) | 1.01 (1.00-1.02) | .23 |
| Transport time (per 5-min increase) | 1.01 (0.99-1.02) | .27 |
| Measures of Access to Care | ||
| Proximity to level I or II trauma center | ||
| Within county | 0.65 (0.59-0.72) | <.001 |
| Adjacent county | 0.98 (0.92-1.04) | |
| No proximate trauma center | 1 [Reference] | |
| Population ≤25 miles of HEMS base (per 10% increase) | 1.00 (1.00-1.01) | .27 |
| Traffic Safety Laws | ||
| Maximum speed limit >65 mph | ||
| Urban highways and interstates | 1.12 (0.96-1.32) | .14 |
| Rural highways and interstates | 1.69 (1.32-2.15) | <.001 |
| Primary enforcement of seat belt laws | 0.88 (0.76-1.02) | .09 |
| Administrative license suspension | 0.86 (0.68-1.08) | .20 |
| Text messaging ban | 0.99 (0.84-1.16) | .91 |
Abbreviations: EMS, emergency medical service; HEMS, helicopter emergency medical service; MVC, motor vehicle crash.