Increased carotid intima-media thickness in men born in east Finland: a twin study of the effects of birthplace and migration to Sweden on subclinical atherosclerosis.

Background: There is a clear east-west difference in coronary heart disease (CHD) mortality and incidence in Finland, people living in east Finland having higher CHD rate. A study of Finnish immigrants to Sweden has suggested that a long stay in Sweden would be associated with reduced CHD risk.
Aim: To determine whether structural and functional markers of subclinical atherosclerosis differ between men originating from east and west Finland, and whether migration to Sweden influences subclinical atherosclerosis.
Method: Carotid intima-media thickness (IMT) and brachial artery flow-mediated dilatation (FMD) with high-resolution ultrasound and a set of cardiovascular risk factors were measured in 76 middle-aged male twin pairs (55 pairs from east and 21 pairs from west Finland) discordant for migration to Sweden.
Results: Among men living in Finland, IMT was significantly higher in men originating from east Finland compared to those from west Finland (0.796 +/- 0.212 versus 0.704 +/- 0.123 mm, P = 0.02). A similar east-west difference was observed in men who had migrated to Sweden (0.766 +/- 0.220 versus 0.686 +/- 0.089 mm, P = 0.03). The east-west difference in IMT persisted after adjustment for the major traditional cardiovascular risk factors. No east-west difference was seen in FMD. Smoking, Framingham risk score and physical activity had a greater impact on IMT in men originating from east compared to west Finland.
Conclusions: Men originating from east Finland, irrespective of their current residence, have a greater degree of subclinical atherosclerosis and they may be more susceptible to the impact of conventional cardiovascular risk factors than men originating from west Finland.