[1] Univ Ulm, Dept Epidemiol, D-89081 Ulm, Germany
[2] Univ Massachusetts, Sch Publ Hlth & Hlth Sci, Dept Biostat & Epidemiol, Amherst, MA 01003 USA
[3] Univ Munster, Inst Epidemiol & Social Med, D-4400 Munster, Germany
[4] Syrian Ctr Tobacco Studies, Aleppo, Syria
[5] Univ Childrens Hosp Munich, Munich, Germany