TABLE 3.
The risk of respiratory symptoms and airways obstruction (AO) in monozygotic versus dizygotic twins
| Monozygotic twins | Dizygotic twins | ||||
| Subjects | Reference | Subjects | Crude OR | Adjusted OR# | |
| Respiratory symptoms | |||||
| Shortness of breath | |||||
| at rest | 58 (2.4) | 1.00 | 211 (2.5) | 1.04 (0.78–1.41) | 1.03 (0.76–1.38) |
| during daily activities¶ | 25 (1.0) | 1.00 | 73 (0.9) | 0.84 (0.52–1.34) | 0.77 (0.49–1.23) |
| during exercise | 292 (11.8) | 1.00 | 1019 (11.9) | 1.00 (0.87–1.16) | 0.96 (0.83–1.11) |
| Chronic cough | 190 (7.8) | 1.00 | 684 (8.0) | 1.03 (0.87–1.23) | 0.99 (0.83–1.18) |
| Chronic phlegm | 130 (5.3) | 1.00 | 507 (5.9) | 1.13 (0.92–1.39) | 1.08 (0.88–1.34) |
| Chronic bronchitis+ | 83 (3.4) | 1.00 | 328 (3.8) | 1.14 (0.89–1.48) | 1.11 (0.86–1.43) |
| Nocturnal awakening | 194 (7.8) | 1.00 | 606 (7.0) | 0.89 (0.75–1.06) | 0.87 (0.73–1.04) |
| Wheeze | 131 (5.3) | 1.00 | 450 (5.2) | 0.98 (0.80–1.21) | 0.95 (0.78–1.18) |
| Airway obstruction | |||||
| FR | 338 (15.2) | 1.00 | 1470 (18.8) | 1.29 (1.12–1.49) | 1.18 (1.02–1.37) |
| LLN | 109 (4.9) | 1.00 | 451 (5.77) | 1.19 (0.95–1.49) | 1.14 (0.91–1.43) |
| Clinical COPD | |||||
| FR-AO + symptoms | 130 (5.2) | 1.00 | 575 (6.6) | 1.29 (1.05–1.59) | 1.17 (0.95–1.44) |
| LLN-AO + symptoms | 59 (2.4) | 1.00 | 218 (2.5) | 1.06 (0.78–1.44) | 0.99 (0.73–1.34) |
Data are presented as n (%) or odds ratio (OR) (95% CI). FR: fixed ratio; LLN: lower limit of normal; COPD: chronic obstructive pulmonary disease. #: multiple logistic regression analysis adjusted for age (as a dichotomous variable dividing the study sample at <60 years and ≥60 years), sex and ever-smoking; ¶: cleaning, cooking and dressing; +: defined according to American Thoracic Society/European Respiratory Society guidelines.