Factors associated with health-related quality of life in Koreans aged over 50 Years: the fourth and fifth Korea National Health and Nutrition Examination Survey.

The Korea National Health and Nutrition Examination Survey (KNHNES) is not a clinical trial registry, but the national health survey conducted by the Government of the Republic of Korea, to gather information on health and nutritional status of Korean population, to plan public health services and health education programs, and to do statistical studies of the efficiency of public health services required for setting up welfare and healthcare policies.