TABLE 3

The risk of respiratory symptoms and airways obstruction (AO) in monozygotic versus dizygotic twins

Monozygotic twinsDizygotic twins
SubjectsReferenceSubjectsCrude ORAdjusted OR#
Respiratory symptoms
 Shortness of breath
  at rest58 (2.4)1.00211 (2.5)1.04 (0.78–1.41)1.03 (0.76–1.38)
  during daily activities25 (1.0)1.0073 (0.9)0.84 (0.52–1.34)0.77 (0.49–1.23)
  during exercise292 (11.8)1.001019 (11.9)1.00 (0.87–1.16)0.96 (0.83–1.11)
 Chronic cough190 (7.8)1.00684 (8.0)1.03 (0.87–1.23)0.99 (0.83–1.18)
 Chronic phlegm130 (5.3)1.00507 (5.9)1.13 (0.92–1.39)1.08 (0.88–1.34)
 Chronic bronchitis+83 (3.4)1.00328 (3.8)1.14 (0.89–1.48)1.11 (0.86–1.43)
 Nocturnal awakening194 (7.8)1.00606 (7.0)0.89 (0.75–1.06)0.87 (0.73–1.04)
 Wheeze131 (5.3)1.00450 (5.2)0.98 (0.80–1.21)0.95 (0.78–1.18)
Airway obstruction
 FR338 (15.2)1.001470 (18.8)1.29 (1.12–1.49)1.18 (1.02–1.37)
 LLN109 (4.9)1.00451 (5.77)1.19 (0.95–1.49)1.14 (0.91–1.43)
Clinical COPD
 FR-AO + symptoms130 (5.2)1.00575 (6.6)1.29 (1.05–1.59)1.17 (0.95–1.44)
 LLN-AO + symptoms59 (2.4)1.00218 (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.