1. Department of Epidemiology and Population Studies, Jagiellonian University, Grzegorzecka 20, 31–531 Kraków, Poland
2. Department of Anthropology, Harvard University, Cambridge, MA 02138, USA
3. Department of Epidemiology, University of Tromso, N–9037 Tromso, Norway
4. Ulleval University Hospital, 0407 Oslo, Norway