Background: Immigrants is an important minority in many countries, but little is known how they are self-selected. We analysed differences in psycho-social and health behavioural factors between international migrants and non-migrants prior to migration in a large cohort of Finnish twins.
Methods: A questionnaire was sent to Finnish twins in 1975 (response rate 89%, N = 26555 twin individuals). Follow-up data on migration and mortality were derived from population registries in Finland and Sweden up to 31 March 2002. In 1998, another questionnaire was sent to Finnish twins migrated to Sweden and their co-twins (response rate 71%, N = 1534 twin individuals). The data were analysed using Cox and conditional logistic regression models.
Results: Life dissatisfaction, higher alcohol use and smoking at baseline predicted future migration. In men additionally, unemployment, neuroticism and extroversion increased the probability to migrate. Similar associations were found for alcohol use in men and smoking in men and women within twin pairs discordant for migration. Twins also reported retrospectively that prior to migration the migrated twin had been less satisfied with his/her educational institution or job and was generally less satisfied with life, used more alcohol (men) and smoked more (women) than the co-twin stayed in Finland.
Conclusion: Migrants are self-selected by health behavioural and personality factors, which may compromise their health. The special requirements of migrants should be recognized in health care.