DATABASE CONSTRUCTION/QUALITY CONTROL Trained nurses will code questionnaires, technicians will enter the data. For quality assurance, 10% of questionnaires will be randomly selected and recoded by another nurse. All data will be inputted twice by different technicians. Duplicate datasets will be compared with the PROC COMPARE application (SAS software) to trace input errors. Data coders and SAS programs will check for internal consistency of questionnaire replies. Non-Gaussian distributions will be normalized by proper transformation. As part of the quality control, descriptive statistics will be generated at 6 month intervals.