[1] Nykobing Falster Hosp, Ctr Epidemiol Res, Lolland Falster Hlth Study, Fjordvej 15, DK-4800 Nykobing F, Denmark
[2] Reg Zealand, Data & Dev Support, Alleen 15, DK-4180 Soro, Denmark
[3] Reg Zealand, Psychiat, Psychiat Res Unit, Faelledvej 6, DK-4200 Slagelse, Denmark
[4] Univ Southern Denmark, Res Unit Gen Practice, JB Winslows Vej 9A, DK-5000 Odense C, Denmark
[5] Univ Copenhagen, Copenhagen Prospect Studies Asthma Childhood, Hosp Herlev Gentofte, Ledreborg Alle 34, DK-2820 Gentofte, Denmark
[6] Slagelse Hosp, Dept Pediat, Ingemannsvej 18, DK-4200 Slagelse, Denmark
[7] Boston Childrens Hosp, Dept Lab Med, Boston, MA USA
[8] Harvard Med Sch, Boston, MA 02115 USA
[9] Univ Copenhagen, Fac Hlth & Med Sci, Dept Clin Med, DK-2200 Copenhagen N, Denmark
[10] Natl Inst Publ Hlth, Dept Hlth & Morbid Populat, Studiestr 6, DK-1455 Copenhagen, Denmark