Shiu Lun Au Yeung1, Tai Hing Lam2. 1. School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China. 2. School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China. Electronic address: hrmrlth@hkucc.hku.hk.