This paper is part of the Thai Nurse Cohort Study (TNCs). The TNCs was planned as a 20-year longitudinal cohort study. In 2009 the base-line survey was performed. A random sample of registered nurses (RNs) who held nursing licenses granted by Thailand Nursing and Midwifery Council (TNMC) as of 2008 were surveyed by mailed-questionnaires and the respondents were enrolled as cohort members. The first wave of the study was carried out as a cross- sectional survey. The sampling method was stratified random sampling with probability proportional to size of nurses in each 10-year age intervals. This paper involved a total of 18,756 members of the cohort then excluded those nurses who did not work in the previous 12 months.