[1] Univ Sidi Mohamed Ben Abdellah, Fac Med Fez, Dept Epidemiol & Publ Hlth, Fes, Morocco
[2] Univ Sidi Mohamed Ben Abdellah, Ctr Hosp Univ Hassan Fez 2, Pneumol Serv, Fes, Morocco
[3] Imperial Coll London, Natl Heart & Lung Inst, Resp Epidemiol Occupat Med & Publ Hlth Grp, Emmanuel Kaye Bldg,Manresa Rd, London SW3 6LR, England