Heredity of chronic bronchitis:A registry-based twin study

SummaryBackgroundSmoking is a major risk factor for lung diseases and lower respiratory symptoms, but since not all smokers develop chronic bronchitis and since chronic bronchitis is also diagnosed in never-smokers, it has been suggested that some individuals are more susceptible to develop chronic bronchitis due to genetics.ObjectiveTo study the relative influence of genetic and environmental factors on the variation in the susceptibility to chronic bronchitis.MethodsIn a population-based questionnaire study of 13,649 twins, 50–71 years of age, from the Danish Twin Registry, we calculated sex-specific concordance rates and heritability of chronic bronchitis. The response rate was 75%.ResultsThe prevalence of chronic bronchitis was 9.3% among men and 8.5% among women. The concordance rate for chronic bronchitis was higher in monozygotic twins than in dizygotic twins among women; 0.30 vs. 0.17, but not among men; 0.15 vs. 0.18. The heritability of chronic bronchitis adjusted for smoking and age was 55% (36–71%) in women, whereas the susceptibility to chronic bronchitis in men for 25% (8–41%) was ascribable to familial environment but not to genetic factors.ConclusionsChronic bronchitis shows a moderate familial aggregation, particularly in women. Increased susceptibility to respiratory disease among female smokers relative to male smokers may have a genetic origin

Apgar score is related to development of atopic dermatitis:cotwin control study

Aim. To study the impact of birth characteristics on the risk of atopic dermatitis in a twin population. Methods. In a population-based questionnaire study of 10,809 twins, 3–9 years of age, from the Danish Twin Registry, we identified 907 twin pairs discordant for parent-reported atopic dermatitis. We cross-linked with data from the Danish National Birth Registry and performed cotwin control analysis in order to test the impact of birth characteristics on the risk of atopic dermatitis. Results. Apgar score, OR (per unit) = 1.23 (1.06–1.44), P=0.008, and female sex, OR = 1.31 (1.06–1.61), P=0.012, were risk factors for atopic dermatitis in cotwin control analysis, whereas birth anthropometric factors were not significantly related to disease development. Risk estimates in monozygotic and dizygotic twins were not significantly different for the identified risk factors. Conclusions. In this population-based cotwin control study, high Apgar score was a risk factor for atopic dermatitis. This novel finding must be confirmed in subsequent studies