Characteristics of the participating players. Results for all players are divided in two groups based on (a) previous concussion history (n = 270) and (b) headings per match (n = 153)*
| Variable | Previous concussions | Headings per match† | ||
|---|---|---|---|---|
| Yes (n = 133) | No (n = 137) | >11 (n = 85) | 0–5 (n = 68) | |
| *Results are shown as the mean (SD) or percentage of valid responses within the group. | ||||
| †Excluding goalkeepers. | ||||
| ‡Data missing for five athletes. | ||||
| Age (years) | 25.1 (4.5) | 26.2 (4.7) | 26.0 (4.7) | 25.3 (4.9) |
| Playing experience in Tippeligaen (years) | 2.8 (2.4) | 3.3 (2.4) | 3.1 (2.4) | 3.2 (2.4) |
| PCSS score (0–120) | 3.8 (6.7) | 4.0 (6.2) | 3.5 (6.2) | 4.8 (7.1) |
| Total number of concussions | 2.0 (1.1) | – | 1.4 (1.4) | 0.7 (0.9) |
| Alcohol intake (AUDIT score; 0–13) | 5.3 (2.7) | 5.1 (2.3) | 5.1 (2.5) | 5.1 (2.3) |
| Other stimulants (yes) | 1.5 | 1.5 | 2.4 | 0‡ |
| Exposure to solvents (yes) | 3.9 | 8.1 | 2.4 | 7.4 |
| General anaesthesia (yes) | 49.2 | 58.1 | 49.4 | 55.9 |
| Headache (monthly or weekly) | 6.3 | 6.7 | 2.4 | 5.9 |
| Migraine (yes) | 5.3 | 9.6 | 5.9 | 4.4 |
| Epilepsy (yes) | 0 | 0.7 | 0 | 0 |
| Depression (yes) | 1.5 | 1.5 | 0 | 2.9 |
| Hyperkinetic activity disorders (yes) | 1.5 | 1.5 | 0 | 0 |
| Learning disabilities | 3.8 | 2.2 | 2.4 | 1.5 |
| Highest education level | ||||
| Primary school or less (⩽9 years) | 6.1 | 6.7 | 0 | 2.9 |
| Secondary school (high school) | 68.7 | 59.0 | 62.4 | 69.1 |
| Tertiary education (college) | 25.2 | 34.3 | 37.6 | 26.5 |
| Nationality | ||||
| Norwegian | 82.6 | 83.1 | 82.4 | 83.8 |
| Other Scandinavian | 6.1 | 8.1 | 8.2 | 5.9 |
| Other European | 8.3 | 5.9 | 5.9 | 7.4 |
| Non-European | 3.0 | 3.0 | 3.6 | 3.0 |
| Playing position | ||||
| Goalkeeper | 10.4 | 9.8 | – | – |
| Defensive player | 13.4 | 25.0 | 43.5 | 2.9 |
| Wingback | 16.8 | 15.9 | 10.6 | 13.2 |
| Central midfielder | 19.2 | 18.2 | 8.2 | 22.1 |
| Other midfielder | 10.4 | 6.8 | 3.5 | 19.1 |
| Wing | 10.4 | 10.6 | 3.5 | 25.0 |
| Attacker | 17.6 | 12.1 | 22.4 | 10.3 |
| Unknown | 1.6 | 1.5 | 8.2 | 7.3 |
| Heading frequency (per match) | ||||
| Never | 1.7 | 0.8 | – | 4.4 |
| 1–5 times | 29.4 | 23.6 | – | 95.6 |
| 6–10 times | 39.5 | 35.8 | – | – |
| 11–20 times | 23.5 | 30.1 | 77.6 | – |
| >20 times | 5.9 | 9.8 | 22.4 | – |