Risk of venous thromboembolism in first- and second-generation immigrants in Sweden

There are ethnic differences in the incidence of venous thromboembolism. This is the first nationwide study to examine whether there is an association between country of birth in first-generation immigrants and first hospitalisation for venous thrombosis (VT) and pulmonary embolism (PE), and to study whether a similar association exists in second-generation immigrants.

The study is a nationwide follow-up study. The study subjects were first- and second-generation immigrants residing in Sweden between January 1, 1964 and December 31, 2007. The reference population comprised first- and second-generation Swedish-born individuals. Standardised incidence ratios (SIRs) for VT and PE, standardised with regard to age, geographic region of residence, time period, and socioeconomic status, were estimated by sex in first- and second-generation immigrants.

First-generation male and/or female immigrants from Greece, Italy, Spain, Finland, Baltic countries, Central Europe, Eastern Europe, Russia, Latin America, Turkey, Iran, and Iraq had a lower risk of VT and/or PE than Swedish-born individuals. The lower risk of VT and/or PE in some first-generation immigrant groups was not replicated in the second generation. However, in certain second-generation immigrant groups, the risk of VT/PE was similar to that in the corresponding parental groups.

Country of birth affects the risk of VT and PE in several immigrant groups. Our study indicates that ethnicity-related inherited and acquired venous thromboembolism risk factors play a role in the aetiology of venous thromboembolism. Ethnic differences in thromboembolism risk even exist in Caucasian European populations, and may thus be important to consider in genetic studies.