Kuhrs et al. BMC Public Health 2012, 12:190 http://www.biomedcentral.com/1471-2458/12/190 Page 3 of 9 Original cohort n=34,393 CVD (ICD10) death: n=1,077 Deaths between 1991-2006 and contact information available: n=404 Interviewed cases: n=98 Figure 2 Selection of cases and controls from the original cohort. of the cohort according to the matching criteria and approached via an invitation letter and telephone con- tact (if telephone number was available). Data collection Relatives of cases and controls themselves were inter- viewed by telephone using a standardized questionnaire. To ensure comparability relatives of cases and controls were both asked first about their own risk factors, fol- lowed by questions of deceased relatives. The question- naire was developed on the basis of the KORA study and tested on randomly selected individuals [25]. In total, the questionnaire consists of 45 closed questions from the following subject areas: Socio-demography and profession: sex, date of birth, country of origin, immi- gration year, school and university degrees, profession, retirement age; Health: subjective assessment of their physical constitution and issues with existing illnesses; Lifestyle factors: smoking habits, alcohol consumption, nutrition and sports activities; Anthropometric informa- tion and Family history of CVD and cancer. For recruitment of participants, the following mea- sures were taken: Bilingual questionnaire and a bilingual interviewer (German and Russian), contact at desired times, interviewing time not longer than 20 minutes, five euro compensation offer, reminder letter after two n=30,500 alive 2,816 death for other causes or loss- to-follow-up Potential controls: n=680 Interviewed controls: n=250 weeks, second reminder letter with advertising gift and newspaper interview with the project manager from the magazine “KOHTAKT-IIIAHC”, issue No. 21 dated 22.05.2006, as well as another personal contact by tele- phone. Data collection took place between August 2009 and February 2010 for cases and between February 2010 and September 2010 for controls. Participant information and consent form Before contact was established, the content of the survey and the data protection rules were explained to potential participants by sending a consent form and information material. By signing the consent form or by a telephone call, the participants declared willingness to participate and assured that they were informed sufficiently on the study and the further use of the data collected. Partici- pation could be withdrawn at any time. Ethical aspects The study was approved by the ethics committee of the medical faculty of Heidelberg University. Statistical analysis After data processing, analysis was carried out using sta- tistical analysis system version 9.2 (SAS 9.2). Data analy- sis was descriptive and analytical. To estimate relative