Kuhrs et al. BMC Public Health 2012, 12:190 http://www.biomedcentral.com/1471-2458/12/190 or socioeconomic status between participants with or without living relatives. However, most of the controls (63%) do also have living relatives as can be extracted from the cohort data. We can also assume that several of those without a relative in our database in fact have one or more relatives, which were unknown to us. Therefore, we assume that a bias due to this aspect is small. We are aware that a possible reporting bias is one of the strongest limitations of our study. However, as is shown in the study of Nelson et al. [46], who used a dual interview protocol in a case-control study where control subjects and their proxy respondents were inter- viewed, the reliability of proxy-derived data was excel- lent for demographic and body habitus measures and all aspects of cigarette smoking history. Proxy reliability was only somewhat lower for questions regarding medi- cations and hormone preparations, alcolhol consump- tion, and recreational physical activity. The causes of death for cases are a broad heterogeneous group of con- ditions with possibly different sets of risk factors. Alco- hol consumption is reported to be only a rather protective factor for Myocardial infarction and cerebro- vascular diseases in low doses, and a high risk factor for high doses [47]. The very high Odds Ratio for alcohol consumption (> 20 g/day in males and > 10 g/day in females) found in our study is therefore a little surpris- ing and should be further evaluated. For this particular factor, a reporting bias must be considered. The causes of death are not based on review of medical records or adjudicated causes of death but solely on death reports and coding with its possible inaccuracies. For compari- son of risk factor prevalences with the German popula- tion we used results from several earlier surveys. Although these data were not obtained in an identical way compared to this study, we think a comparison is appropriate. We have selected those surveys which we consider as most appropriate. Conclusions Results of this study may partly explain the observation of earlier studies that CVD mortality is significantly lower in Aussiedler than in Germans. The reported lower prevalences of known risk factors of CVD such as alcohol consumption, high cholesterol, diabetes and smoking (in women) could contribute to a lower risk of CVD. Although the relatively low alcohol consumption is surprising, given the known high alcohol consumption in the former Soviet Union, it is possible that the Aus- siedler had behavioral patterns that differed from the native population in the former Soviet Union. A new prospective cohort study on this group of migrants has just started and will elucidate this issue. Page 8 of 9 Abbreviations KORA study: Cooperative health research in the Augsburg region; 95%-CI: 95 percent confidence interval; SMR: Standardized mortality ratio; CVD: Cardiovascular and cerebrovascular diseases; NRW: North Rhine-Westphalia; ICD: International statistical classification of diseases and related health problems; SAS: Statistical analysis system; OR: Odds ratio; BMI: Body mass index; SBP: systolic blood pressure; DBP: Diastolic blood pressure Acknowledgements The study was funded by a grant of the German Research Foundation, Graduate College 793: “Epidemiology of communicable and chronic noncommunicable diseases and their interrelationships”. Authors’ contributions EK collected the data, performed the calculations, developed the figures and drafted the manuscript. VW provided knowledge regarding statistical and methodological problems. HB conceived the study. 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