[1] Aarhus Univ Hosp, Dept Clin Epidemiol, DK-8000 Aarhus C, Denmark
[2] Aalborg Hosp, DK-8000 Aarhus C, Denmark
[3] Randers Cent Hosp, Dept Med, DK-8900 Randers, Denmark
[4] Aalborg Hosp, Dept Occupat Med, DK-9000 Aalborg, Denmark
[5] Inst Canc Epidemiol, Danish Canc Soc, DK-2100 Copenhagen O, Denmark
[6] Aarhus Univ Hosp, Dept Med 5, DK-8000 Aarhus C, Denmark