Table 1. Baseline Demographics and Exposure Characteristics.
| Variable | Value | P Value | |||
|---|---|---|---|---|---|
| Total Sample (N = 352) | Heading Quartile | ||||
| 1 and 2 (n = 121) | 3 (n = 101) | 4 (n = 130) | |||
| No. of 12-mo headers, median (IQR) | 165 (70-296) | 638 (522-791) | 2346 (1538-3824) | ||
| Age, median (IQR), y | 23 (21-28) | 26 (22-33) | 24 (21-31) | 21 (20-24) | <.001 |
| Educational level, mean (SD), y | 15.6 (2.8) | 16.6 (2.6) | 15.7 (3.2) | 14.7 (2.3) | <.001 |
| CogState ISRL score, mean (SD) | 9.5 (1.8) | 10.0 (1.7) | 9.3. (1.8) | 9.2 (1.9) | <.001 |
| Years playing soccer at similar frequency, median (IQR)a | 11 (7-16) | 10 (5-16) | 12 (8-18) | 11 (7-15) | .26 |
| Male sex, No. (%) | 256 (73) | 68 (56) | 82 (81) | 106 (82) | <.001 |
| Race/ethnicity, No. (%) | |||||
| White | 235 (67) | 87 (72) | 73 (72) | 75 (58) | .17 |
| African American | 61 (17) | 18 (15) | 11 (11) | 32 (25) | |
| Asian | 20 (6) | 7 (6) | 6 (6) | 7 (5) | |
| Native Hawaiian or Pacific Islander | 4 (1) | 1 (1) | 1 (1) | 2 (2) | |
| Declined to answer | 32 (9) | 8 (7) | 10 (10) | 14 (11) | |
| Past or present smoker, No. (%) | 102 (29) | 39 (32) | 31 (31) | 32 (25) | .37 |
| Alcoholic drinks per wk, No. (%) | |||||
| 0 | 84 (24) | 19 (16) | 23 (23) | 42 (32) | .04 |
| 1-2 | 149 (42) | 52 (43) | 41 (41) | 56 (43) | |
| 3-7 | 93 (26) | 38 (31) | 31 (31) | 24 (19) | |
| 8-14 | 24 (7) | 11 (9) | 6 (6) | 7 (5) | |
| >14 | 2 (1) | 1 (1) | 0 | 1 (1) | |
| Lifetime concussion(s), No. (%)a | |||||
| 0 | 233 (66) | 78 (64) | 63 (62) | 82 (63) | .44 |
| 1 | 56 (16) | 23 (19) | 17 (17) | 16 (12) | |
| ≥2 | 67 (19) | 18 (15) | 20 (20) | 29 (21) | |
| APOE genotype, No. (%)b | |||||
| ε2/ε2 | 2 (1) | 1 (1) | 0 | 1 (1) | .91 |
| ε2/ε3 | 53 (15) | 21 (17) | 14 (14) | 18 (14) | |
| ε2/ε4 | 10 (3) | 4 (3) | 2 (2) | 4 (3) | |
| ε3/ε3 | 215 (61) | 69 (57) | 66 (65) | 80 (62) | |
| ε3/ε4 | 67 (19) | 25 (21) | 18 (18) | 24 (19) | |
| ε4/ε4 | 4 (1) | 1 (1) | 0 | 3 (2) | |
Abbreviations: APOE, apolipoprotein E; IQR, interquartile range; ISRL, International Shopping List Delayed Recall.
a
Data missing in 6 participants.
b
Variant (rs7412) failed in 1 participant (T-T homozygote).