Evidence for genetic associations between asthma, atopy, and bronchial hyperresponsiveness: a study of 8- to 18-yr-old twins.
We measured asthma in the last 12 mo, diagnosed by a respiratory physician at interview; atopy, defined by a positive skin prick test to any of eight common allergens; and bronchial hyperresponsiveness (BHR) to hypertonic saline, in 381 twin pairs aged 8 to 18 yr selected from the Australian Twin Registry-183 monozygous (MZ) and 198 dizygous (DZ). The associations between twins, as measured by an odds ratio, were greater in MZ pairs compared with DZ pairs for asthma: 25.6 (95% confidence interval 11.3- 57.8) versus 1.9 (1.0-3. 5); atopy: 14.6 (7.1-30.1) versus 2.5 (1.4- 4.5); and BHR: 14.1 (6. 4-31.0) versus 4.2 (2.1-8.6) (all p < 0.002). The associations between each pair of traits within an individual were slightly greater than the association between one trait in a twin and the other trait in the cotwin (cross-trait cross-pair) in MZ pairs. Further, the associations in MZ pairs were greater than in DZ pairs (p < 0.05). Under the assumptions of the classic twin model, these data suggest that the strong cross-sectional associations between these three traits are due to an overlap between the genetic factors involved in each of these three traits.
Clarke
J R
JR
Respiratory & Cystic Fibrosis Unit, The Birmingham Children's Hospital NHS Trust, Birmingham, United Kingdom.
Jenkins
M A
MA
Hopper
J L
JL
Carlin
J B
JB
Mayne
C
C
Clayton
D G
DG
Dalton
M F
MF
Holst
D P
DP
Robertson
C F
CF
D000293:Adolescent; D001249:Asthma / Q000175:diagnosis / Q000209:etiology / Q000235:genetics* / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000175:diagnosis / Q000209:etiology / Q000235:genetics*; D001985:Bronchial Provocation Tests / Q000706:statistics & numerical data; D002648:Child; D004200:Diseases in Twins / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000175:diagnosis / Q000209:etiology / Q000235:genetics*; D008297:Male; D016017:Odds Ratio; D012882:Skin Tests / Q000706:statistics & numerical data; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014739:Victoria