The Risk of Venous Thrombosis in Different Immigrant Groups in the Netherlands
Authors: Rezende Suely M , Lijfering Willem M. , Rosendaal Frits R. , Cannegieter Suzanne C. 
Published: October 2019

Abstract
Abstract 3393

Background:
Ethnic differences in the incidence of venous thrombosis have been appreciated for many years. However, with few exceptions, most of the studies on this subject were based on administrative databases from North America and China. The aim of this study was to investigate the risk of venous thrombosis in different first and second generation immigrant groups included in a large population-based case-control study, performed in the Netherlands.

Methods:
This study was performed using data from the MEGA study (Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis-study), a large, population based case-control study on risk factors for venous thrombosis from the Netherlands. Inclusion criteria consisted of patients and controls whom information were available on the country of birth. For the analysis related to immigration background, patients were compared with random digit dialing (RDD) controls. First generation immigrants were classified as those who were born outside the Netherlands. Second generation immigrants were similarly defined as first generation immigrants, except that second immigrants were born in the Netherlands, while both parents were born in one of aforementioned other countries. In total, 6899 participants were included, of whom 4300 patients and 2599 RDD controls. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated as estimates of the relative risk, and were adjusted for age, sex, body mass index, smoking, hormonal factors, alcohol consumption, physical activity and malignancy by unconditional logistic regression.

Results:
The risk of venous thrombosis varied according to the region of birth (Table 1). When compared with the Dutch, Eastern Europeans reached the highest and East/Southeast Asians the lowest risk of venous thrombosis with OR of 2.35, (95% CI, 1.09–4.59) and 0.44 (95% CI, 0.29–0.68), respectively after multivariate adjustments. Caribeans showed an intermediate lower risk of 0.69 (95% CI, 0.36–1.30) after multivariate adjustments (Table 1). We did not observe a major difference on the risk for VT between first and second generation immigrants, although the number of second generation immigrants was small for some groups. Subgroup analysis did not show major differences according to immigration groups, except for Eastern Europeans, who had a higher risk for unprovoked event with OR of 3.79 (95% CI, 1.44–9.97) and East/Southeast Asians with higher risk for pulmonary embolism with OR of 0.60 (95% CI, 0.36–1.0) (Table 2). In comparison with Dutch controls, East/Southeast Asians controls had lower prevalence of factor V Leiden (6% and 1%, respectively) and prothrombin mutation (2% and 1%, respectively) but higher blood group non-O (54% and 62%, respectively). Risk of VT in East/Southeast Asians adjusted for age, sex, factor V Leiden and blood group non-O was 0.53 (95% CI, 0.35–0.80). Analysis of a panel of procoagulant, anticoagulant, profibrinolytic and genetic factors are underway and is expected to be available before the ASH conference of 2012.

Conclusions:
The risk of VT varies in different populations. The risk of VT in East/Southeast Asians was the lowest and was virtually unchanged after adjustment for several environmental and genetic known risk factors for VT.

Disclosures:
No relevant conflicts of interest to declare.