[1] Department of Epidemiology and Social Medicine,
[2] University of Aarhus,undefined
[3] Vennelyst Boulevard 6,undefined
[4] DK-8000 Aarhus C,undefined
[5] Denmark Tel: +45 8942 3129 Fax: +45 8942 3182 E-mail: lh@soci.au.dk,undefined
[6] Randers Hospital,undefined
[7] Denmark,undefined