Table 1: Descriptive characteristics of a sample of 575 Danish twins, 20–51 years of age.

N (%)

Demographic data
 Age35.9 (8.2)
 Males240 (41.7)
 Females335 (58.3)
 MZ twins191 (33.2)
 DZ twins384 (66.8)
 BMI25.3 (4.6)
 Smoking ever262 (45.6)
Clinical traits
 Urticaria ever151 (26.3)
 Urticaria in the past 12 months24 (4.2)
 Urticaria currently0 (0)
 Asthma337 (58.6)
 Hay fever309 (53.7)
 Atopic dermatitis137 (23.8)
Paraclinical traits
 Positive skin prick test318 (55.3)
 Serum total IgE54.4 (4.3)

MZ: monozygotic; DZ: dizygotic; BMI: body mass index.
All numbers are prevalence (%) except age (years, mean); BMI (kg/m2, mean); and serum total IgE (KIU/L, geometric mean).