Methods
Study design
This population-based cross-sectional study explored QoL in
elderly Korean individuals aged 60 years and older using data
collected in the health interviews and health examinations of the
Fourth Korean National Health and Nutrition Examination Survey
(KNHANES IV 2008), a nationwide representative cross-sectional
survey of the noninstitutionalized Korean population conducted
by the Korean Centers for Disease Control and Prevention. This
study was approved by the institutional review board of the Korean
Centers for Disease Control and Prevention (No. 2008-04EXP-01-C).
KHANES IV 2008 used a stratified, multistage, probability-cluster,
complex sampling design to select household units based on region, sex, and age. Data were assigned weights to assure the equal
probability of being sampled and of covering missing data to
represent Korea’s population. A total weight was assigned to each
participant in three steps: (a) calculation of the base weight (1/final
probability), (b) adjustment for nonresponses, and (c) poststratification adjustment to match the 2005 National Census Registry population control totals. Final probability was calculated by
multiplying four factors: the probability of the primary sampling
unit being selected (264,186 sampling units), the probability of a
segment of the primary sampling unit being selected, the probability of each household being selected (each sampling unit
included approximately 60 households), and the probability of an
individual being selected. The health interview was performed by
trained examiners, and diagnoses were made following scientific
and medical principles based on a physician’s decision about
whether or not participants had a given disease