[Characteristics of smoking and secondhand smoke exposure in monozygotic and dizygotic twins: results from an international twin study]

[Hungarian twin studies: results of four decades]

Twin studies play a role in examining the contribution of genetic variations and environmental factors responsible for the determination of phenotypic variables and of genetic linkage between genotypes. Hungarian twin studies, supported by three twin registries (among them two twin-database), date back to 1970s. Studies mainly focused on various congenital abnormalities, the effect of contraceptive pills and folic acid on the frequency of twin pregnancies, as well as psychosexual and alcohol consumptional behaviors. Monogenic Mendelian inheritance of lactose (mal)absorption was demonstrated for the first time. Hungarian Twin Registry was founded in 2007, which contributed to the current understanding on the background of several disorders, e.g. metabolic syndrome and atherosclerosis. As part of an international twin study, among others, arterial stiffness, central blood pressure, carotid intima/media thickness, venous biomechanics, body composition, lung function and smoking characteristics were also assessed. Absence of genetic background in non-alcoholic fatty liver disease and high inheritance of carotid plaque characteristics were demonstrated for the first time. The review also aims to summarize future plans of the Hungarian Twin Registry.

[Environmental factors that influence smoking habits of monozygotic and dizygotic twins]

INTRODUCTION

Smoking habits are influenced by environmental (family, friends) and psychologic factors.

AIM

To investigate environmental factors which influence the smoking habits of monozygotic and dizygotic twins.

METHOD

45 monozygotic and 23 dizygotic twin pairs (age 35±16 years) completed a questionnaire.

RESULTS

Maternal non-smoking decreases the risk of smoking of the twin children by 53%, while this effect accounts for 49% by the father. Dizygotic twins are more influenced by parents (70%) than monozygotics (31-36%). If the twin or non-twin sibling does not smoke, the risk that the twin individual starts smoking, is decreased by 86% both in monozygotic and dizygotic twins. If an individual smoking is present in the fraternity and he or she does not attempt to quit, the risk of smoking increases 8.3-fold. The role of fraternity is more important in males and youth.

CONCLUSIONS

The parents' and the siblings' exemplary behaviour helps to avoid smoking initiation of young twins.