RESEARCH DESIGN AND METHODS
NHANES 2005–2006 was conducted by the National Center for Health Statistics (11). NHANES is designed to be representative of the U.S. civilian noninstitutionalized population using a complex, multistage probability sample. Participants are interviewed in their homes and subsequently receive a physical and laboratory examination in a
mobile examination center. Among eligible subjects in 2005–2006, 77.7% were
interviewed and 74.9% were examined (11).