NHANES is an ongoing series of cross-sectional surveys
conducted by the National Center for Health Statistics (NCHS) of
the Centers for Disease Control and Prevention (CDC). The survey
is nationally representative of the civilian, non-institutionalized
US population. NHANES oversamples certain subpopulations to
increase the precision of estimates.21 Participants have a
household interview followed by a physical examination in a
mobile examination center (MEC). Written informed consent was
obtained from all participants and parental permission for
participants aged