Chapter 1. Demography (1999-2018)

Section 1. Component Description

The NHANES 1999-2018 Demographics File provides the interview and MEC examination status variable, two-year and four-year sample weights, and selected demographic variables such as gender, age, race/ethnicity, education, marital status, country of birth, pregnancy status, total family and household income, and ratio of income to poverty.',

This updated Demographics file includes new information on citizenship, years of U.S. residence, educational attainment, school attendance, household size, characteristics of the household reference person, and an indicator variable for the month of exam. The household reference person is the first household member, 18 years of age or older who is listed on the screener questionnaire household member roster who owns or rents the residence where members of the household reside. Descriptions of the variables that have been added to this updated Demographics file are included in the Data Processing and Editing section of the file documentation.'

Please note that several questionnaire items that were part of the Family and Sample Person Demographics questionnaires are not included in the NHANES 1999-2000 public data release file due to concerns about data disclosure and confidentiality protection.

There are several variables with new categories in the 2007-2008 Demographics File. The variables with additional categories are the survey participants (DMDBORN2) and the household reference person's country of birth (DMDHRBR2) and the household (INDHHIN2) and the family income variable (INDFMIN2). An additional variable, an indicator variable for the month of exam, has been included.

In 2007-2008 a new sampling methodology was implemented. We oversampled all Hispanics, not just Mexican Americans (Table 1). In addition, for each of the race/ethnicity domains, the 12-15 and 16-19 year age domains were combined and the 40-59 year age minority domains were split into 10 year age domains 40-49 and 50-59 (Table 2). This has led to an increase in the number of participants aged 40+ and a decrease in 12-19 year olds from previous cycles. Lastly, we no longer oversampled pregnant women. Based on these changes some variables have been modified from previous release cycles.

Table1. Unweighted sample size and percent by race/ethnicity from NHANES 2005-06 and 2007-08 for examined participants

Table2. Unweighted sample size and percents by age groups from NHANES 2005-06 and 2007-08 for examined participants

Disclosure risks and issues pertaining to confidentiality protection prevent NCHS from releasing all NHANES Demographics variables publicly. Additional information may be publicly accessible through the NCHS Research Data Center (RDC). The RDC website has information about special request data files. The RDC website is found on the NCHS home page.

The sample design for NHANES 2011-14 includes an oversample of Asian Americans (Table 3). Therefore, a new variable (RIDRETH3) is included to describe the participant’s race and Hispanic origin.

Table 3. Unweighted sample size and percentage by race/Hispanic origin, from NHANES 2009-2010 and 2011-2012 for examined participants

[1] Non-Hispanic Asians were included in the “Other” category in 2009-10.

Similar to previous release cycles, the 2011-2012 demographics file includes a variable for age in years at screening (RIDAGEYR) for all participants. A new variable has been added to denote the age in years at examination (RIDEXAGY) for participants aged 2 to 19 years. Age in months at screening (RIDAGEMN)\xa0is reported for participants aged 0 to 24 months. Age in months at examination (RIDEXAGM) is reported for participants aged 0 to 19 years. Due to increasing concerns about potential disclosure risks, information on age in months at screening and at examination for participants in other age groups are no longer included in the public release file but are available through the NCHS Research Data Center (RDC).

Starting in 2011, more detailed information on veterans in the U.S. is collected in NHANES. Two new variables were released in the 2011-2012 demographic file to denote whether the participant had served on active duty in the U.S. Armed Forces (DMQMILIZ), and for those who had, the second was to denote whether the participant had ever served in a foreign country during a time of armed conflict or on a humanitarian or peace-keeping mission (DMQADFC). DMQMLIZ replaces the veteran status question (DMQMILIT) collected in previous NHANES cycles that asked if the participant had served in the Armed Forces of the U.S. Additional information for these veterans is available through the NCHS RDC.

Three new variables were included in the 2011-2012 NHANES demographics file to report more detailed information on participants’ household composition: DMDHHSZA (number of children aged 5 years or younger in the household), DMDHHSZB (number of children aged 6-17 years old in the household), and DMDHHSZE (number of adults aged 60 years or older in the household).

There are several variables with new categories in the 2011-2012 demographics file. The variables with updated categories are: the survey participant’s country of birth (DMDHRBR4), and the language used for the audio-computer-assisted self-interview.

The sample design for NHANES 2011-14, 2015-2016 includes an oversample of Asian Americans (Table 4). The variable RIDRETH3 is included to describe the participant’s race and Hispanic origin.

Table 4. Unweighted sample size and percentage by race/Hispanic origin, from NHANES 2007-2010 and 2011-2014 for examined participants

[1] Non-Hispanic Asians were included in the “Other” category in 2007-10.