[1] Univ Turin, Dept Publ Hlth Sci, Piazza Polonia 94, I-10126 Turin, Italy
[2] Northwestern Univ, Feinberg Sch Med, Dept Surg, 633 N St Clair St, Chicago, IL 60611 USA
[3] NIVEL Netherlands Inst Hlth Serv Res, POB 1568, NL-3500 BN Utrecht, Netherlands
[4] Vrije Univ Amsterdam Med Ctr, Amsterdam Publ Hlth Res Inst, Dept Gen Practice & Elderly Care Med, Boechorststr 7, NL-1081 BT Amsterdam, Netherlands
[5] Univ Utrecht, Dept Sociol, POB 80-115, NL-3508 TC Utrecht, Netherlands
[6] Univ Utrecht, Dept Human Geog, POB 80-115, NL-3508 TC Utrecht, Netherlands