[1] Aarhus Univ, Dept Clin Epidemiol, Aarhus, Denmark
[2] Univ Copenhagen, Dept Publ Hlth, Sect Social Med, Copenhagen, Denmark
[3] Boston Univ, Sch Publ Hlth, Dept Epidemiol, Boston, MA USA
[4] Harvard Sch Publ Hlth, Dept Social & Behav Sci, Boston, MA USA
[5] Univ Copenhagen, Dept Publ Hlth, Oester Farimagsgade 5,POB 2099, DK-1014 Copenhagen, Denmark