Table 1. Demographic characteristics of cases and controls.
| Cases (N = 30) | Controls (N = 224) | |
| Characteristics | n (%) | n (%) |
| Residency (Regional population†) | ||
| Northern Taiwan (6,910,467) | 7 (23.3) | 58 (25.0) |
| Northwestern Taiwan (3,487,664) | 5 (16.7) | 36 (16.1) |
| Central Taiwan (4,485,041) | 9 (30.0) | 69 (30.8) |
| Southwestern Taiwan (3,408,726) | 5 (16.7) | 34 (15.2) |
| Southern Taiwan (3,742,589) | 2 (6.7) | 16 (7.1) |
| Eastern Taiwan (1,028,692) | 2 (6.7) | 13 (5.8) |
| Gender | ||
| Male | 13 (43.3) | 104 (46.4) |
| Female | 17 (56.7) | 120 (53.6) |
| Age | ||
| 16–25 | 5 (16.7) | 40 (17.9) |
| 26–35 | 13 (43.3) | 100 (44.6) |
| 36–45 | 5 (16.7) | 37 (16.5) |
| 46–55 | 2 (6.7) | 15 (6.7) |
| >55 | 5 (16.7) | 32 (14.3) |
| Childbearing-aged (16–45 y/o) woman | 11 (36.7) | 81 (36.2) |
| Blood group type | ||
| O | 16 (53.6) | 94 (41.3) |
| A | 7 (21.4) | 65 (29.8) |
| B | 5 (17.9) | 43 (19.7) |
| AB | 2 (7.1) | 22 (9.1) |
| Educational level | ||
| High school and below | 16 (53.6) | 81 (35.1) |
| College and above | 14 (46.4) | 143 (64.9) |
| Occupation | ||
| Laborer | 7 (23.3) | 41 (18.3) |
| Businessman/employee | 17 (56.7) | 125 (55.8) |
| Student/unemployed | 6 (20.0) | 58 (25.9) |
†
Average of end-year population, 2008–2012.