1. Faculty of Pharmacy, School of Pharmaceutical Science; National Yang-Ming University; Taipei 112 Taiwan
2. Department of Medicine, College of Medicine; National Taiwan University Hospital; Taipei 100 Taiwan
3. Graduate Institute of Epidemiology and Preventive Medicine, College of Public Health; National Taiwan University; Taipei 100 Taiwan
4. Institute of Statistical Science, Academia Sinica; Taipei 115 Taiwan
5. Department of Population Medicine; Harvard Medical School and Harvard Pilgrim Health Care Institute; Boston MA 02215 USA