Summary
Differences in genetic influence on death from CHD between males and females have
been reported. Haemostatic factors have consistently been associated with risk for
coronary heart disease (CHD), but sex differences in genetic architecture have not
been studied. This study in middle-aged twins investigates whether there are sex differences
in means and in genetic and/ or environmental variance components of haemostatic risk
factors for CHD. A total of 93 monozygotic twin pairs (44 male and 49 female) and
116 dizygotic twin pairs (36 male, 40 female and 40 opposite sex) were available for
this study. Structural equation modelling was used to estimate the relative influence
of genetic and environmental factors on variation in levels of fibrinogen, tissue
plasminogen activator (tPA) antigen and von Willebrand factor (vWF). Mean levels of
tPA and vWF increased with age. Oral contraceptive pill (OCP) and menopause had significant
influences on levels of fibrinogen and tPA. Genetic influences explained 39, 66 and
72% of the variation in levels of fibrinogen, tPA and vWF, respectively. No quantitative
or qualitative differences of genetic influences on haemostatic levels were seen between
males and females. Haemostatic factors may account fora significant part of the genetic
risk for cardiovascular disease. No difference in genetic architecture for levels
of fibrinogen, tPA or vWF was observed between males and females.
Keywords
Twins - haemostasis - heritability - sex differences - oral contraceptive pill