[1] Univ Groningen, Med Ctr, Dept Pulmonol, NL-9700 RB Groningen, Netherlands
[2] Univ Groningen, Beatrix Childrens Hosp, Med Ctr, Dept Pediat, NL-9700 RB Groningen, Netherlands
[3] Univ Groningen, Beatrix Childrens Hosp, Med Ctr, Dept Pediat Pulmonol, NL-9700 RB Groningen, Netherlands
[4] Univ Groningen, Med Ctr, Dept Epidemiol, NL-9700 RB Groningen, Netherlands