Variation in mortality by country of birth in Northern Ireland: a record linkage study.

The study of health differences between those residing in the same country but originating in different countries is a potential source of insight into the causes of ill-health. Within Northern Ireland, those born in England, Wales, the Republic of Ireland and outside of the British Isles have a lower mortality risk than the Northern Ireland born; however, these differentials are largely explained by the demographic and socio-economic characteristics of these migrants. Conversely, the Scottish born residing in Northern Ireland have higher mortality than the Northern Ireland born, especially from ischemic heart disease, suggesting that the Scottish immigrants maintain the health disadvantage of their country of birth.