cross-sectional study was conducted using data from the
National Health and Nutrition Examination Survey (NHANES)
from the 2003-2004 and 2005-2006 cycles, which uses a
stratified, multistage probability sample.15 In 2003-2006, certain
groups (eg, blacks and Mexican Americans, persons with
low income, and adults aged 60 years) were oversampled
for statistical reliability.