| Variable | MHI with LOC or PTA (n (%)) | MHI without LOC or PTA (n (%)) | OR (95% CI) | p Value | p Value for heterogeneity |
| Trauma mechanism | |||||
| Pedestrian/cyclist versus vehicle | 196 (11) | 67 (8.9) | 2.3 (1.6–3.4) | 0.000 | 0.215 |
| Fall from (some) height* | 442 (26) | 147 (19) | 1.7 (1.2–2.3) | 0.002 | 0.877 |
| Ejected from vehicle | 34 (2.0) | 17 (2.3) | 1.7 (0.7–4.0) | 0.234 | 0.717 |
| Symptoms | |||||
| Persistent anterograde amnesia† | 174 (10) | 21 (2.8) | 1.1 (0.6–1.8) | 0.806 | 0.257 |
| Vomiting | 166 (10) | 65 (8.6) | 2.5 (1.6–3.6) | 0.000 | 0.844 |
| PTA, average duration (min) | 18.3 | 0.0 | 1.7 (1.3–2.3)‡ | 0.000 | n/a |
| Loss of consciousness | 1419 (83) | 0 (0.0) | 1.9 (1.3–2.6) | 0.000 | n/a |
| Headache | |||||
| Diffuse | 719 (42) | 286 (38) | 1.1 (0.8–1.5) | 0.467 | 0.447 |
| Localised | 275 (16) | 160 (21) | 1.3 (0.9–1.9) | 0.199 | 0.107 |
| Post-traumatic seizure | 13 (0.8) | 3 (0.8) | 2.7 (0.8–9.8) | 0.122 | 0.487 |
| External evidence of injury | |||||
| Signs of skull fracture | 35 (2.0) | 12 (1.6) | 25 (13–47) | 0.000 | 0.028 |
| Contusion of the skull | 591 (35) | 329 (44) | 2.1 (1.6–2.9) | 0.000 | 0.063 |
| Signs of facial fracture | 120 (7.0) | 68 (9.0) | 2.0 (1.3–3.2) | 0.003 | 0.253 |
| Contusion of face | 874 (51) | 400 (53) | 1.0 (0.8–1.4) | 0.922 | 0.638 |
| Multiple injuries | 373 (22) | 173 (23) | 1.8 (1.3–2.5) | 0.000 | 0.814 |
| Neurological examination | |||||
| Neurological deficit | 146 (8.5) | 61 (8.1) | 1.8 (1.1–2.8) | 0.011 | 0.230 |
| GCS score deterioration at 1 h | 40 (2.3) | 10 (1.3) | 3.9 (2.0–7.6) | 0.000 | 0.723 |
| Miscellaneous | |||||
| Age (y) | 40.2 | 42.2 | 1.2 (1.1–1.3)§ | 0.000 | n/a |
| Use of anticoagulant therapy | 35 (2.0) | 33 (4.4) | 2.2 (1.0–4.5) | 0.038 | 0.370 |
| Intoxication | |||||
| Mild | 151 (8.8) | 91 (12) | 0.8 (0.4–1.3) | 0.355 | 0.712 |
| Moderate | 279 (16) | 145 (19) | 0.6 (0.4–0.9) | 0.023 | 0.372 |
| Severe | 177 (10) | 52 (6.9) | 1.0 (0.6–1.7) | 0.977 | 0.258 |
GCS, Glasgow Coma Scale; LOC, loss of consciousness; MHI, minor head injury; n/a, not applicable; OR, odds ratio; PTA, post-traumatic amnesia.
Shown are the prevalence of the risk factors, Mantel–Haenszel odds ratios (OR), p values of the ORs and p values for heterogeneity of the ORs across the two subgroups according to the Breslow–Day statistic
*Fall from (some) height included falls from any elevation.
†Persistent anterograde amnesia was defined as the inability to capture and retain any new information in memory.
‡Per 60 min of PTA.
§Per 10 years.