Occupational and environmental risk factors
| Risk factor | Total, n (%) | Male, n (%) | Female, n (%) |
| Exposure to pesticides or herbicides | 517 (33.6) | 390 (39.2) | 127 (23.6) |
| Information not provided | 25 (1.6) | 16 (1.6) | 9 (1.7) |
| Age of exposure to pesticides or herbicides | |||
| <18 years of age | 185 (12.1) | 128 (12.9) | 57 (10.6) |
| 18–36 | 239 (15.6) | 190 (19.1) | 49 (9.1) |
| 37–55 | 84 (5.5) | 64 (6.4) | 20 (3.7) |
| ≥56 | 9 (0.6) | 8 (0.8) | 1 (0.2) |
| Head injury | 244 (15.9) | 186 (18.7) | 58 (10.8) |
| Information not provided | 21 (1.4) | 12 (1.2) | 9 (1.7) |
| Age of head injury | |||
| Mean (SD) | 26.3 (17.6) | 26.2 (16.5) | 26.9 (20.8) |
| Range | 2–82 | 3–67 | 2–82 |
| Head injury with loss of consciousness | 165 (10.8) | 128 (12.8) | 37 (6.9) |
| Well water drinking | 82 (5.3) | 55 (5.5) | 27 (5.0) |
| Information not provided | 34 (2.2) | 21 (2.1) | 13 (2.4) |
| Number of years drinking well water | |||
| Mean (SD) | 18.7 (12.4) | 18.3 (12.9) | 19.4 (11.6) |
| Range | 2–50 | 2–50 | 4–40 |
| Worked in high-risk occupations | 504 (32.9) | 425 (42.7) | 79 (14.7) |
| Number of high-risk occupations worked throughout of life | |||
| One | 293 (19.1) | 226 (22.8) | 67 (12.5) |
| Two | 115 (7.5) | 107 (10.7) | 8 (1.5) |
| Three | 52 (3.4) | 48 (4.8) | 4 (0.7) |
| Four | 29 (1.9) | 29 (2.9) | 0 (0.0) |
| Five or more | 15 (0.9) | 15 (1.5) | 0 (0.0) |
| Worked or lived on a farm for over 1 year | 360 (23.5) | 236 (23.7) | 124 (23.1) |
| Information not provided | 27 (1.8) | 18 (1.8) | 9 (1.6) |
| Had metal poisoning | 22 (1.4) | 17 (1.7) | 5 (0.9) |
| Information not provided | 34 (2.2) | 21 (2.1) | 13 (2.4) |
| Had brain infection (encephalitis) | 31 (2.0) | 20 (2.0) | 11 (2.1) |
| Information not provided | 21 (1.4) | 12 (1.2) | 1 (0.2) |
High-risk occupations included welding, metal melting, galvanisation, milling, petrochemistry, agriculture, wood processing, textile or industrial painting. n=1532.