Both the NHANES and NHIS surveys are subject to the CDC/NCHS Ethics Review Board (ERB) to ensure that appropriate human subjects protections are provided, in compliance with 45 CFR part 46. All statistical analyses were carried out with STATA 10.1 software [23], using the "svy" command to incorporate information on the appropriate weights, primary sampling units and strata for correct variance estimation. This analysis is limited to the adult (18 years and over) samples in both surveys. Estimates are age-standardized based on the 2000 U.S. Census results, using 10-year age intervals.
