Unit of Population Epidemiology, Division of Primary Care Medicine, Department of Primary Care Medicine, Geneva University Hospitals, 1211, Geneva 14, Switzerland; Geographic Information Research and Analysis in Population Health (GIRAPH) Group, Geneva University Hospitals, Geneva and Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland; Laboratory of Geographical Information Systems (LASIG), School of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.