Table 2 Univariate associations between variables and injury risk among combat engineer recruits
Variable group | Variable | Strata | N | Injury incidence (%) | Hazard ratio (95% CI) | p-value (Wald statistic) |
|---|---|---|---|---|---|---|
Age | Age | <20.0 years | 722 | 44.3 | 1.00 | Referent |
20.0-24.9 years | 690 | 46.7 | 1.12 (0.96-1.31) | 0.14 | ||
25.0-29.9 years | 144 | 50.7 | 1.30 (1.01-1.68) | 0.04 | ||
≥30.0 years | 77 | 62.3 | 1.81 (1.34-2.46) | <0.01 | ||
BMI | BMI | <18.5 kg/m2 | 27 | 74.1 | 2.32 (1.48-3.64) | <0.01 |
18.5-24.9 kg/m2 | 845 | 46.9 | 1.00 | Referent | ||
25.0-29.9 kg/m2 | 628 | 43.5 | 0.93 (0.80-1.09) | 0.37 | ||
≥30 kg/m2 | 127 | 54.3 | 1.38 (1.07-1.78) | 0.02 | ||
Prior tobacco use | Smoked ≥100 cigarettes in life | No | 1000 | 44.8 | 1.00 | Referent |
Yes | 632 | 49.8 | 1.17 (1.01-1.35) | 0.04 | ||
Age started smoking | Never smoked | 745 | 46.7 | 1.00 | Referent | |
<13 years | 84 | 50.0 | 1.08 (0.79-1.49) | 0.63 | ||
13-16 years | 550 | 47.5 | 1.02 (0.87-1.20) | 0.81 | ||
≥17 years | 254 | 44.2 | 0.92 (0.75-1.14) | 0.47 | ||
Days smoked in 30 days before ENG training | None | 1098 | 46.0 | 1.00 | Referent | |
1-9 days | 146 | 45.9 | 1.00 (0.77-1.29) | 0.99 | ||
10-19 days | 92 | 46.7 | 1.00 (0.74-1.37) | 0.98 | ||
≥20 days | 297 | 49.8 | 1.11 (0.92-1.33) | 0.27 | ||
Cigarettes smoked in 30 days before ENG training | None | 1112 | 46.2 | 1.00 | referent | |
1-9 cigarettes/day | 303 | 47.2 | 1.00 (0.83-1.21) | 0.98 | ||
10-19 cigarettes/day | 146 | 45.2 | 0.98 (0.76-1.26) | 0.86 | ||
≥20 cigarettes/day | 71 | 54.9 | 1.36 (0.98-1.88) | 0.07 | ||
Days of smokeless tobacco use in 30 days before ENG training | None | 1331 | 48.5 | 1.00 | Referent | |
1-9 days | 72 | 37.5 | 0.73 (0.50-1.07) | 0.11 | ||
10-19 days | 61 | 38.4 | 0.74 (0.41-1.05) | 0.14 | ||
≥20 days | 168 | 48.7 | 1.01 (0.61-1.32) | 0.12 | ||
Amount of smokeless tobacco use in 30 days before ENG training | None | 1341 | 48.2 | 1.00 | Referent | |
≤3/4 cans, plugs | 125 | 41.2 | 0.84 (0.67-1.05) | 0.14 | ||
1 to 1-3/4 cans, plugs | 121 | 41.7 | 0.84 (0.69-1.09) | 0.11 | ||
≥2 cans, plugs | 43 | 51.2 | 1.16 (0.76-1.77) | 0.50 | ||
Prior physical activity | Physical activity before ENG training, compared to other of same age and sex | Much less active | 70 | 67.1 | 2.46 (1.75-3.47) | <0.01 |
Less active | 293 | 59.7 | 1.83 (1.44-2.33) | <0.01 | ||
Average | 421 | 42.8 | 1.12 (0.88-1.42) | 0.38 | ||
More active | 583 | 43.7 | 1.13 (0.90-1.42) | 0.29 | ||
Much more active | x265 | 40.0 | 1.00 | Referent | ||
Exercise or sports frequency 2 months before ENG training | ≤1 time/week | 187 | 58.3 | 1.76 (1.40-2.22) | <0.01 | |
2-4 time/week | 907 | 48.2 | 1.26 (1.07-1.49) | <0.01 | ||
≥5 time/week | 538 | 40.3 | 1.00 | Referent | ||
Running/jogging Frequency before ENG training | ≤1 time/week | 478 | 52.3 | 1.46 (1.15-1.86) | <0.01 | |
2-4 times/week | 926 | 45.6 | 1.17 (0.93-1.47) | 0.17 | ||
5-7 times/week | 227 | 39.6 | 1.00 | Referent | ||
Time running/jogging before ENG training | ≤1 month | 484 | 50.4 | 1.38 (1.10-1.72) | <0.01 | |
2-6 months | 876 | 46.6 | 1.19 (0.97-1.47) | 0.11 | ||
|  |  | ≥7 months | 273 | 40.7 | 1.00 | Referent |
Weight training frequency before ENG training | ≤1 time/week | 646 | 51.5 | 1.28 (1.04-1.57) | 0.02 | |
2-4 times/week | 699 | 43.8 | 0.99 (0.81-1.22) | 0.95 | ||
5-7 times/week | 286 | 43.4 | 1.00 | Referent | ||
Time weight training before ENG training | ≤1 month | 671 | 50.7 | 1.30 (1.08-1.56) | <0.01 | |
2-6 months | 544 | 45.2 | 1.12 (0.92-1.36) | 0.26 | ||
≥7 months | 417 | 42.2 | 1.00 | Referent | ||
Prior injury | Prior lower limb injury | No | 1234 | 45.3 | 1.00 | Referent |
Yes | 399 | 51.1 | 1.21 (1.03-1.43) | 0.02 | ||
Prior injury prevent activities ≥1 week | No prior injury | 1234 | 45.3 | 1.00 | Referent | |
No | 131 | 47.3 | 1.04 (0.80-1.36) | 0.76 | ||
Yes | 267 | 52.8 | 1.30 (1.08-1.57) | <0.01 | ||
Totally recovered from prior injury | No prior injury | 1229 | 45.2 | 1.00 | Referent | |
No | 18 | 61.1 | 2.17 (1.19-3.93) | 0.01 | ||
Yes | 380 | 50.5 | 1.18 (1.00-1.39) | 0.05 | ||
Demo-graphics | Component | Active Army | 972 | 47.8 | 1.00 | Referent |
National Guard | 463 | 45.1 | 0.89 (0.76-1.05) | 0.17 | ||
Army Reserve | 198 | 44.9 | 0.96 (0.76-1.20) | 0.69 | ||
Educational level | <High school graduate | 99 | 57.6 | 1.39 (1.05-1.82) | 0.02 | |
High school graduate | 1315 | 46.3 | 1.00 | Referent | ||
Some college | 150 | 46.0 | 1.01 (0.79-1.30) | 0.93 | ||
≥College graduate | 52 | 40.4 | 0.91 (0.59-1.40) | 0.66 | ||
Unknown | 17 | 41.2 | 0.83 (0.40-1.75) | 0.63 | ||
Race/ethnicity | White | 1122 | 45.5 | 1.00 | Referent | |
Black | 239 | 49.0 | 1.09 (0.89-1.34) | 0.39 | ||
Hispanic | 191 | 49.2 | 1.08 (0.87-1.34) | 0.50 | ||
Other | 78 | 53.8 | 1.32 (0.96-1.81) | 0.09 | ||
Missing | 3 | 0.0 | a | a | ||
Marital status | Single, never married | 1380 | 50.0 | 1.00 | Referent | |
Married | 238 | 46.1 | 1.16 (0.96-1.42) | 0.13 | ||
| Â | Â | Other | 15 | 53.3 | 1.16 (0.58-2.33) | 0.68 |