[1] Nanjing Med Univ, Sch Nursing, Nanjing 210029, Peoples R China
[2] Chinese Univ Hong Kong, Fac Med, Nethersole Sch Nursing, Hong Kong 999077, Peoples R China
[3] Imperial Coll London, Natl Heart & Lung Inst, Sch Publ Hlth, London W12 7RQ, England
[4] Lanzhou Univ, Sch Nursing, Lanzhou 730000, Peoples R China