TABLE 3.
Adjusted Population Measure Incidence Rate Ratios (IRRs) for Major Trauma Events Across the 9 Study Sites: Resuscitation Outcomes Consortium Epistry-Trauma Project, United States and Canada, 2005–2007
| Major Traumaa (n = 6841), IRR (95% CI) | Death in Fieldb (n = 978), IRR (95% CI) | Penetrating Injuryc (n = 1315), IRR (95% CI) | Intentional Injuryd (n = 1704), IRR (95% CI) | |
| Men, % | 1.0002 (1.00005, 1.0004) | 1.0003 (1.00009, 1.0006) | … | … |
| Unemployment, % | 1.06 (1.05, 1.07) | 1.03 (1.01, 1.05) | 1.05 (1.03, 1.06) | 1.05 (1.04, 1.07) |
| Non–primary language use, %e | ||||
| Quartile 1 (Ref) | 1.00 | 1.00 | 1.00 | 1.00 |
| Quartile 2 | 0.87 (0.75, 1.00) | 0.70 (0.55, 0.90) | 0.86 (0.69, 1.05) | … |
| Quartile 3 | 1.02 (0.87, 1.21) | 0.59 (0.44, 0.78) | 0.85 (0.66, 1.09) | … |
| Quartile 4 | 1.23 (1.02, 1.49) | 0.48 (0.34, 0.67) | 0.65 (0.47, 0.88) | … |
| Median household size | 0.68 (0.62, 0.75) | 0.74 (0.60, 0.92) | 0.73 (0.60, 0.88) | 0.67 (0.57, 0.80) |
| Median age, y | 1.03 (1.02, 1.04) | … | … | … |
| Adjusted median household income, $e | ||||
| Quartile 1 (Ref) | 1.00 | 1.00 | 1.00 | 1.00 |
| Quartile 2 | … | 0.91 (0.72, 1.15) | 0.64 (0.52, 0.79) | 0.68 (0.56, 0.83) |
| Quartile 3 | … | 0.69 (0.51, 0.94) | 0.51 (0.39, 0.68) | 0.51 (0.40, 0.66) |
| Quartile 4 | … | 0.59 (0.40, 0.88) | 0.36 (0.25, 0.51) | 0.44 (0.32, 0.60) |
| High school diploma, % | 0.99 (0.98, 0.99) | 0.98 (0.97, 0.99) | 0.98 (0.97, 0.99) | 0.98 (0.97, 0.99) |
| Site | ||||
| 1 (Ref) | 1.00 | 1.00 | 1.00 | 1.00 |
| 2 | 0.94 (0.74, 1.20) | 1.18 (0.80, 1.74) | 1.11 (0.81, 1.53) | 1.02 (0.78, 1.33) |
| 3 | 1.44 (1.14, 1.82) | 1.30 (0.90, 1.88) | 1.34 (1.00, 1.81) | 1.32 (1.00, 1.76) |
| 4 | 0.45 (0.34, 0.59) | 0.83 (0.53, 1.29) | 0.49 (0.33, 0.73) | 0.49 (0.36, 0.68) |
| 5 | 1.69 (1.25, 2.29) | 1.41 (0.88, 2.27) | 1.63 (1.13, 2.34) | 1.57 (1.10, 2.23) |
| 6 | 0.57 (0.44, 0.74) | 0.35 (0.22, 0.57) | 0.31 (0.21, 0.48) | 0.36 (0.25, 0.51) |
| 7 | 1.97 (1.54, 2.51) | 1.44 (0.98, 2.14) | 2.21 (1.60, 3.04) | 2.42 (1.85, 3.19) |
| 8 | 0.39 (0.30, 0.51) | 0.47 (0.31, 0.72) | 0.18 (0.12, 0.27) | 0.12 (0.09, 0.17) |
| 9 | 0.34 (0.25, 0.45) | 1.10 (0.70, 1.71) | 0.44 (0.29, 0.66) | 0.36 (0.26, 0.49) |
Note. CI = confidence interval. Data were based on 4129 census tracts. Estimates were obtained via multivariable negative binomial models with patient count as the outcome. The census tract was the unit of analysis. The total number of census tracts included in the regression analyses was larger than that included in the clustering analysis (4129 vs 3893) because noncontiguous census tracts were included in nongeospatial models. Main effect terms from the final models are included; however, interactions were also tested in each of these models. Ellipses indicate covariates dropped from the final model.
Interactions included Site × Men, Site × High School Diploma, Household Size × Age, Non–Primary Language Use × Men, Unemployment Rate × Age, and Non–Primary Language Use × Age (P < .001), as well as Men × Unemployment Rate, Men × Household Size, Non–Primary Language Use × Household Size, Unemployment Rate × Household Size, and Unemployment Rate × High School Diploma (P < .05).
Interactions included Site × Men, Site × Age, Unemployment Rate × Household Size, Median Income × Men, and Income × High School Diploma (P < .01).
Interactions included Median Income × Non–Primary Language Use, Non–Primary Language Use × Household Size, and Unemployment Rate × Household Size (P < .01), as well as Median Income × Men, Median Income × Household Size, and Median Income × Age (P < .05).
Interactions included Unemployment Rate × Household Size, Unemployment Rate × Age, Median Income × Age, and Unemployment Rate × High School Diploma (P < .01).
Quartile 1 = 0–25th percentile; quartile 2 = 26th–50th percentile; quartile 3 = 51st–75th percentile; quartile 4 = 76th–100th percentile.