[1] Karolinska Inst, Unit Biostat, Div Epidemiol, Inst Environm Med, SE-17177 Stockholm, Sweden
[2] Karolinska Inst, Inst Environm Med, Div Epidemiol, SE-17177 Stockholm, Sweden
[3] Stockholm Cty Council, Ctr Epidemiol & Social Med, Hlth Care Serv, Stockholm, Sweden
[4] Karolinska Inst, Karolinska Univ Hosp, Clin Epidemiol Unit, Dept Med, SE-17177 Stockholm, Sweden