Changing risk factor patterns for cardiovascular and cerebrovascular diseases (CVD) in a large cohort of migrants
Project team: Heiko Becher, Andreas Deckert
External collaborators: Dr. Christa Meisinger, Helmholz-Zentrum München
Funding: DFG (GRK 793)
Funding period: 2009-2013
Status: completed
Background, previous results and current knowledge
Migrant studies are relevant in epidemiologic research. They have shown a great impact of migration on health and mortality outcomes and indicate a significant impact of genetic and environmental as well as lifestyle factors on mortality. One problem in migrant studies is the fact that migrants are not representative of the population of their country of origin. Thus, country-specific risk factor patterns may therefore not be applicable to the migrants. Nevertheless, it appears likely that risk factor patterns of the country of origin are brought by the migrants with them and particular efforts to modify this pattern may improve health outcomes.
Since 1990, more than 2 million ethnic Germans (Aussiedler) migrated from countries of the former Soviet Union (FSU) to Germany. Due to a high CVD mortality of the average Russian population and low socio-economic status (SES) of Aussiedler in Germany, it could be assumed that their CVD mortality is higher than that of autochthonous Germans (despite of the Aussiedler not being representative for the FSU population. )
In a recently conducted retrospective cohort study (Becher et al., 2007), a total of 34,393 Aussiedler from the FSU were enrolled who had migrated to North-Rhine Westphalia, Germany’s most populous federal state, aged at least 15 years upon arrival. Vital status was assessed through record linkage at municipal population registries. For deceased persons, cause of death was established at the state statistical office.
Until 2005 the cohort accumulated 344,457 person-years. Vital status was ascertained for 96.7% of the cohort and 2,580 deaths were observed of which 746 deaths (29%) occurred after 31.12.2002. 1,025 (39.7%) cohort members died of diseases of the circulatory system (ICD-10: I00.I99) (among these 361 after 31.12.2002), the majority of them from ischaemic heart disease (428 persons) and cerebrovascular disease (210 persons).
The SMR of cardiovascular diseases relatively to mortality of all Germans was 0.89 (95% CI: 0.85-0.92) for FSU-immigrants. There was no difference in mortality risk observed between ischaemic heart disease (ICD-10: I20-I25) and cerebral infarction/cerebrovascular disease (ICD-10: I60-I69). Sex, year of arrival, and duration of residence in Germany did not show an significant effect on mortality from these causes.
The temporal trend, however, showed a convergence of the CVD rates in both groups, with a decreasing trend for the total German population and an almost constant mortality rate for the Aussiedler.
Contrasting with the initial hypothesis, CVD mortality among Aussiedler was not only lower compared to the country of origin, but surprisingly also lower than in the German population. Possible explanations are selection effects of the ancestors during the process of migration to Russia or a risk factor distribution which is, contrary to available data, highly different to that of the population of the former SU. In addidion, a different health behaviour than the average Russian population that may have influenced the risk factor profile of the Aussiedler.
A second cohort was established within the 2nd round of the GRK. Cancer incidence and mortality among Aussiedler who have moved to the Saarland is currently investigated. This cohort comprises of 25,000 Aussiedler It will provide a comparably large number of CVD cases, however the follow-up is currently ongoing so that final numbers cannot be given.
A third cohort is being established in the Augsburg area in collaboration with the Helmholtz Zentrum München. This will be a prospective cohort with about 1500 individuals. It is planned to collect individual risk factors and blood samples.
In total, we estimate conservatively that at least 600 deaths of circulatory diseases occurred after 31.12.2001.
Aim of the Study
Since no data on individual risk factors were collected in the original cohort study, hypotheses on underlying mechanisms are speculative only. Therefore, we plan to further investigate cardiovascular risk patterns of the Aussiedler and – for time-varying covariables - their temporal change after resettlement. This study will contribute greatly to interpret already analysed surprising mortality patterns of these diseases in Aussiedler in Germany.
Study design
With a nested case-control study we will investigate risk factor patterns and magnitude of risks for cardiovascular and cerebrovascular diseases within two AMOR-cohorts (North-Rhine Westphalia and Saarland). From the original cohort of 34,393 members who initially settled in North-Rhine Westphalia, 1025 deaths of the circulatory system have been observed until the end follow-up date December 31, 2005. The second cohort of Aussiedler to the federal state of Saarland with a follow-up until end of 2006 will contribute a similar number of deaths. Cases are defined as migrants who immigrated from the FSU to North-Rhine-Westphalia and Saarland who died from CVD after 31.12.2002. This date is fixed in order to maximize response and to minimize recall bias. The expected number of eligible cases is around 600. Next-of-kin information is available though the registry which includes family status and names of next-of-kin. Individuals without family data will not be included.
Two controls groups are planned matched individually by sex and age at date of death of the case (1:2 matching). The first control group consists of deceased individuals who died of causes unrelated to major risk factors for the disease of interest, the second control group consists of individuals currently alive.
Field procedures
We will develop procedures which are in accordance to data protection laws on one side and which are likely to yield a sufficiently large number of cases and controls from the available pool. Since for all cohort members we have an ID number for family, it is possible to contact next-of-kin if available.
Next-of-kin interviews will be performed with a self-administered questionnaire which will be developed (cases and control group 1). Control group 2 will be interviewed directly.
In collaboration with the Helmholz-Zentrum München (Wichmann, Meisinger, Holle, Mielk) a study with Aussiedler in the Augsburg region is planned. This study will be performed as a prospective cohort with a retrospective component. All Aussiedler who migrated to the Augsburg region will be included in the study. All individuals currently alive will be invited for interview and to provide a blood sample. Genetic and lifestyle risk factors for cardiovascular diseases and for diabetes will be investigated.
Time frame
Year 1: development of questionnaire, field organisation,
Year 2: field work, monitoring
Year 3: finalization of data collection, analysis, report writing
(preliminary) Title of dissertations:
Changing risk factor patterns for cardiovascular diseases: A nested case-control study in a cohort of migrants from the Former Soviet Union
Literature
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Mortality from external causes among ethnic German immigrants from former Soviet Union countries, in Germany. European Journal of Public Health 16:376-82.
Ronellenfitsch U, Kyobutungi C, Becher H, Razum O (2006)
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