Genetic factors may play a prominent role in the development of coronary heart disease dependent on important environmental factors

OBJECTIVE The aim of the study was to examine whether various lifestyle factors modify genetic influences on coronary heart disease (CHD). DESIGN The effect of lifestyle factors [including smoking, sedentary lifestyle, alcohol intake and body mass index (BMI)] on risk of CHD was evaluated via Cox regression models in a twin study of gene-environment interaction. Using structure equation modelling, we estimated genetic variance of CHD dependent on lifestyle factors. SUBJECTS In total, 51 065 same-sex twins from 25 715 twin pairs born before 1958 and registered in the Swedish Twin Registry were eligible for this study. During the 40-year follow-up, 7264 incident CHD events were recorded. RESULTS Smoking, sedentary lifestyle and above average BMI were significantly associated with increased CHD incidence. The heritability of CHD decreased with increasing age, as well as with increasing levels of BMI, in both men and women. CONCLUSIONS The difference in the genetic component of CHD as a function of BMI suggests that genetic factors may play a more prominent role for disease development in the absence of important environmental factors. Increased knowledge of gene-environment interactions will be important for a full understanding of the aetiology of CHD.