| Monozygotic (n = 46 pairs) | Dizygotic | ||
| Same sex (n = 23 pairs) | Opposite sex (n = 20 pairs) | ||
| Number of individuals or twin pairs (%) | |||
| Age (years) | |||
| 50–54 | 12 (26.1) | 0 (0.0) | 0 (0.0) |
| 55–59 | 13 (28.3) | 0 (0.0) | 0 (0.0) |
| 60–64 | 7 (15.2) | 4 (17.4) | 1 (5.0) |
| 65–69 | 9 (19.6) | 4 (17.4) | 11 (55.0) |
| 70–74 | 3 (6.5) | 12 (52.2) | 7 (35.0) |
| 75–79 | 2 (4.4) | 3 (13.0) | 1 (5.0) |
| Sex | |||
| Female | 25 (54.4) | 16 (69.6) | 20 (100.0) |
| Male | 21 (45.6) | 7 (30.4) | |
| Smoking | |||
| Smoker | 14 (15.2) | 9 (19.6) | 10 (25.0) |
| Concordance | 40 (87.0) | 16 (69.6) | 12 (60.0) |
| History of atopic disease* | |||
| Yes | 27 (29.3) | 14 (30.4) | 13 (32.5) |
| Concordance | 29 (63.0) | 15 (65.2) | 11 (55.0) |
| History of psoriasis | |||
| Yes | 8 (8.7) | 2 (4.3) | 5 (12.5) |
| Unknown | 2 (2.2) | 1 (2.2) | 2 (5.0) |
| Concordance | 38 (82.6) | 20 (87.0) | 13 (65.0) |
| Farm exposure | |||
| Yes | 1 (1.1) | 2 (4.3) | 1 (2.5) |
| Unknown | 0 (0.0) | 2 (4.3) | 0 (0.0) |
| Concordance | 45 (97.8) | 21 (91.3) | 19 (95.0) |
*Atopic diseases include asthma, atopic dermatitis, and allergy.