1. Department of Statistics and Actuarial Science, The University of Hong Kong , Pokfulam, Hong Kong SAR 999077, China
2. Department of Epidemiology and Biostatistics, School of Public Health, Peking University , Beijing 100191, China
3. Key Laboratory of Molecular Cardiovascular Sciences (Peking University), Ministry of Education , Beijing 100191, China
4. Department of Biostatistics, Columbia University , New York, NY 10032, USA