Intermarriage and health: Mortality among Finnish migrants in Sweden by spousal country of birth

BACKGROUND: Finnish migrants in Sweden experience a mortality disadvantage relative to the native population in part due to health behaviours. Interaction between migrants and natives may lead to a convergence of health behaviours and thereby mortality between the groups. Finnish migrants who are married to a native Swede may thus have mortality rates that are more similar to the Swedish population compared to those married to fellow Finns. Conversely, mortality rates of migrants married to a fellow Finn may more closely resemble those of the population in Finland. METHODS: We use register data to identify all Finnish migrants aged 40-64 in Sweden in 1999 who were married to a native Swede or a fellow Finn. We identify reference groups in both Sweden and Finland, using a combination of inverse probability weighting and direct matching to adjust for differences in sociodemographic characteristics between the groups. We analyse mortality from all causes, CVD, alcohol and smoking related causes during 2000-2017. RESULTS: Compared to Finnish migrant men married to a fellow Finn, migrant men who are married to a native Swede have lower mortality rates, closer to that of the native population of Sweden. This difference is largely explained by sociodemographic characteristics, although lower levels of all-cause and CVD mortality remain after adjustment. By contrast, migrant women married to a native Swede have higher smoking-related mortality, closer to that of native Swedish women. Migrant women married to a fellow Finn have lower smoking-related mortality, closer to that of Finnish-born women in Finland. This pattern is especially pronounced when adjusting for sociodemographic characteristics. CONCLUSIONS: Being married to a native is associated with lower all-cause and CVD mortality for migrant men and higher smoking-related mortality for migrant women. Depending on gender and risk factor intermarriage can be either protective or detrimental for migrant health. KEY MESSAGES: • The mortality risk of Finnish migrants in Sweden vary by spousal country of birth but if intermarriage is protective or detrimental for health depends on gender and risk factor. • Being married to a native Swede is associated with lower CVD mortality for Finnish migrant men and higher smoking-related mortality for Finnish migrant women.