Table 1 Descriptive characteristics of the study population (N = 12242)a
|  | Total twins (N = 12242) | MZ twins (N = 8244) | DZ twins (N = 3998) |  |
|---|---|---|---|---|
| Â | N (%) | N (%) | N (%) | P value* |
Age, years (mean, SD) | 38.8 (11.5) | 38.9 (11.6) | 38.7 (11.2) | 0.550 |
BMI, kg/m2 (mean, SD) | 23.4 (2.9) | 23.3 (2.9) | 23.5 (2.9) | 0.075 |
Overweight | 3760 (30.7) | 2529 (30.7) | 1231 (30.8) | 0.197 |
Obesity | 785 (6.4) | 507 (6.1) | 278 (7.0) | 0.066 |
Region | ||||
 South | 8250 (67.4) | 5622 (68.2) | 2628 (65.7) | - |
 North | 3240 (26.5) | 2124 (25.8) | 1116 (27.9) | 0.060 |
 West | 752 (6.1) | 498 (6.0) | 254 (6.4) | 0.445 |
Marital status | ||||
 Live alone | 2839 (23.2) | 1892 (23.0) | 947 (23.7) | - |
 Married | 9380 (76.6) | 6334 (76.8) | 3046 (76.2) | 0.489 |
Educational attainment | ||||
 Primary | 1681 (13.7) | 1494 (18.1) | 780 (19.5) | - |
 Secondary | 8266 (67.5) | 5637 (68.4) | 2629 (65.8) | 0.082 |
 Tertiary | 2274 (18.6) | 1103 (13.4) | 578 (14.5) | 0.967 |
Cigarette smoking status | ||||
 Never | 6561 (53.6) | 4359 (53.4) | 2162 (54.1) | - |
 Former | 263 (2.1) | 168 (2.0) | 95 (2.4) | 0.454 |
 Current | 5418 (44.3) | 3677 (44.6) | 1741 (43.5) | 0.351 |
 Light | 917 (7.5) | 588 (7.1) | 329 (8.2) | 0.072 |
 Moderate to heavy | 4501 (36.8) | 3089 (37.5) | 1412 (35.3) | 0.064 |
 Cigarette pack-yearsb (mean, SD) | 15.2 (12.7) | 15.4 (12.9) | 14.9 (12.4) | 0.351 |
Alcohol drinking status | ||||
 Never | 8035 (65.6) | 5408 (65.6) | 2627 (65.7) | - |
 Former | 156 (1.3) | 106 (1.3) | 50 (1.3) | 0.886 |
 Current | 4029 (32.9) | 2717 (33.0) | 1312 (32.8) | 0.912 |
Regular physical activity | ||||
 No | 5045 (41.2) | 3392 (41.1) | 1653 (41.3) | - |
 Yes | 5661 (46.2) | 3817 (46.3) | 1844 (46.1) | 0.877 |
 Unclear | 1511 (12.3) | 1016 (12.3) | 495 (12.4) | 0.981 |