the interview. Written informed consent was obtained from all subjects who were interviewed and/or gave DNA samples before the beginning of the studies. The collection of the informed consent as well as blood samples followed the recommendations given in the Declaration of Helsinki and its amendments. Data collection was approved by the hospital district of Helsinki and Uusimaa, the ethical committee for epidemiology and public health (HUS 136/E3/01). A flowchart of the overall study design is shown in Figure 1.
