Dorly J H Deeg1, Hans-Werner Wahl2. 1. VU University Medical Center/LASA, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands. 2. Department of Social and Environmental Gerontology, German Centre for Research on Ageing, University of Heidelberg, Bergheimer Strasse 20, 69115 Heidelberg, Germany.