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Genetic and environmental risk factors for asthma: a cotwin-control study
D L Duffy1, C A Mitchell, N G Martin
1Epidemiology Unit, Queensland Institute of Medical Research, Brisbane, Australia.
American Journal of Respiratory and Critical Care Medicine
|March 28, 1998
Summary
Indoor allergens like dust mites are direct causes of asthma, while pollen allergies may be linked to genetic factors. This study differentiates environmental triggers from genetic predispositions in complex respiratory conditions.
Area of Science:
- Genetics
- Environmental Health
- Immunology
Background:
- Complex diseases like asthma and atopy have unclear genetic and environmental causes.
- Differentiating disease causes from consequences is challenging in genetic conditions.
Purpose of the Study:
- To identify risk factors for wheezing and bronchial hyperresponsiveness.
- To distinguish between direct environmental causes and genetic predispositions in asthma development.
Main Methods:
- Utilized a cotwin-control study design within a larger twin-family study.
- Compared monozygotic (MZ) and dizygotic (DZ) twin pairs discordant for wheezing history.
- Assessed sensitization to indoor allergens (house dust, cat, cockroach) and outdoor allergens (grass pollens, fungi) via skin prick tests.
Main Results:
- In MZ twins, house dust mite sensitization was the strongest asthma discriminator, followed by cat and cockroach allergens.
- DZ twins additionally differed in sensitization to grass pollens and fungi.
- Serum markers (haptoglobin, magnesium, alpha-1-antitrypsin) showed no significant differences between discordant twins.
Conclusions:
- Indoor allergens are likely direct environmental causes of asthma.
- Pollen allergy in asthmatics may be an epiphenomenon, linked to genetic correlations between asthma and allergic diathesis.
- This study highlights the distinct roles of indoor and outdoor allergens in asthma etiology.