• Component Description
• Eligible Sample
• Interview Setting and Mode of Administration
• Quality Assurance & Quality Control
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • SDDSRVYR - Data Release Number
  • RIDSTATR - Interview/Examination Status
  • RIDEXMON - Six month time period
  • RIAGENDR - Gender
  • RIDAGEYR - Age at Screening Adjudicated - Recode
  • RIDAGEMN - Age in Months at Screening - Recode
  • RIDAGEEX - Age in Months at Exam - Recode
  • RIDRETH1 - Race/Ethnicity - Recode
  • DMQMILIT - Served in the US Armed Forces
  • DMDBORN2 - Country of Birth - Recode
  • DMDCITZN - Citizenship Status
  • DMDYRSUS - Length of time in US
  • DMDEDUC3 - Education Level - Children/Youth 6-19
  • DMDEDUC2 - Education Level - Adults 20+
  • DMDSCHOL - Now attending school?
  • DMDMARTL - Marital Status
  • DMDHHSIZ - Total number of people in the Household
  • DMDFMSIZ - Total number of people in the Family
  • INDHHIN2 - Annual Household Income
  • INDFMIN2 - Annual Family Income
  • INDFMPIR - Ratio of family income to poverty
  • RIDEXPRG - Pregnancy Status at Exam - Recode
  • DMDHRGND - HH Ref Person Gender
  • DMDHRAGE - HH Ref Person Age
  • DMDHRBR2 - HH Ref Person Country of Birth
  • DMDHREDU - HH Ref Person Education Level
  • DMDHRMAR - HH Ref Person Marital Status
  • DMDHSEDU - HH Ref Person's Spouse Education Level
  • SIALANG - Language of SP Interview
  • SIAPROXY - Proxy used in SP Interview?
  • SIAINTRP - Interpreter used in SP Interview?
  • FIALANG - Language of Family Interview
  • FIAPROXY - Proxy used in Family Interview?
  • FIAINTRP - Interpreter used in Family Interview?
  • MIALANG - Language of MEC Interview
  • MIAPROXY - Proxy used in MEC Interview?
  • MIAINTRP - Interpreter used in MEC Interview?
  • AIALANG - Language of ACASI Interview
  • WTINT2YR - Full Sample 2 Year Interview Weight
  • WTMEC2YR - Full Sample 2 Year MEC Exam Weight
  • SDMVPSU - Masked Variance Pseudo-PSU
  • SDMVSTRA - Masked Variance Pseudo-Stratum

National Health and Nutrition Examination Survey

2009-2010 Data Documentation, Codebook, and Frequencies

Demographic Variables & Sample Weights (DEMO_F)

Data File: DEMO_F.xpt

First Published: September 2011

Last Revised: NA

Component Description

The Demographics File provides data on the following topics:

• Survey participant’s household interview and examination status
• Interview and examination sample weights
• Masked variance units
• Language of questionnaires used for the interviews conducted in the household and in the mobile examination center
• Use of proxy or interpreter during the interviews
• The six-month time period when the examination was performed
• Pregnancy status
• Household and family income
• Household and family sizes
• Demographic information about the household reference person
• Other selected demographic information such as gender, age, race/ethnicity, education, school attendance, marital status, military service status, country of birth, citizenship, and years of U.S. residence

Disclosure risks and issues pertaining to confidentiality protection prevent NCHS from releasing all of the NHANES demographic variables publicly. Additional information may be accessed through the NCHS Research Data Center (RDC). Instructions for requesting use of these data are available at the RDC website (https://www.cdc.gov/rdc/)

Eligible Sample

All survey participants who have a household interview record are included in the Demographics File. Questions in the Demographics File provide family-level and individual-level information. The target age groups for the Demographics questions vary by the topic. Please review the NHANES 2009-2010 Family and Sample Person Demographics Questionnaires and the codebook carefully.

Interview Setting and Mode of Administration

The Family and Sample Person Demographics questionnaires were asked, in the home, by trained interviewers using the Computer-Assisted Personal Interviewing (CAPI) system. The survey participants selected the language of interview (English or Spanish) or requested that a translator be used. Hand cards showing response categories or information that survey participants needed to answer the questions were used for some questions. The hand cards were printed in English and Spanish. The interviewer directed the respondent to the appropriate hand card during the interview. When necessary, the interviewers assisted survey participants by reading the response choices listed on the hand card.

Persons 16 years of age and older and emancipated minors were interviewed directly. A proxy provided information for survey participants who were under 16 years of age and for individuals who could not answer the questions themselves.

The NHANES 2009–2010 interview and examination procedures manuals and questionnaires are available on the NHANES website at: https://wwwn.cdc.gov/nchs/nhanes/continuousnhanes/default.aspx?BeginYear=2009.

Quality Assurance & Quality Control

The NHANES computer-assisted personal interview (CAPI) software program, that was used to collect the interview data, had built-in data edit and consistency checks to reduce data entry errors. The data edit checks alerted the interviewer when unusual or potentially erroneous data values were recorded. The consistency checks were used to alert the interviewer when the recorded information was inconsistent with previous data entries or respondent characteristics, such as the respondent’s age. Questionnaire “skip” patterns were pre-programmed in the CAPI system to reduce respondent burden. Online information screens provided the interviewers with standardized descriptions of the terminology and concepts that were used in the questionnaires.

After data collection, interview records were reviewed by the NHANES field office staff for accuracy and completeness. A subset of the household interviews was verified by re-contacting the survey participants. The interviewers were required to record interviews periodically and the audio-taped interviews were reviewed by NCHS and contractor staff. The NHANES quality assurance and quality control procedures are described in the field procedures manuals that are available on the NHANES website.

Data Processing and Editing

Frequency counts were checked, “skip” patterns were verified, and the reasonableness of question responses were reviewed. Edits were made to some variables to ensure the completeness, consistency, and analytic usefulness of the data. Edits were also made, when necessary, to address data disclosure concerns.

SDDSRVYR: This variable represents the two-year data release cycle number. A value of “6” denotes NHANES 2009–2010.

RIDSTATR: This status code is used to identify whether a participant was both interviewed at home and examined in the mobile examination center, or was only interviewed in the home but never went through the examination.

RIDEXMON: This variable indicates the six month time period when the examination was performed. A value of “1” indicates November 1^st through April 30^th; a value of “2” indicates May 1^st through October 31^st.

RIDAGEYR: Age in years, at the time of the screening interview, is reported for survey participants between the ages of 1 and 79 years of age. All responses of age 80 years and older are coded as ‘80’.  The reporting of age in single years for adults 80 years and older was determined to be a disclosure risk. In NHANES 2009-2010, the weighted mean age for participants 80 years and older is 84 years.

Each participant’s actual or imputed date of birth was used to calculate RIDAGEYR. The procedure that NCHS used to impute age at screener, when the date of birth is missing or refused but the participant’s age in years is provided, is as follows: If the month of birth is missing or not given, it is imputed as 7 (July). If the day of birth is missing or not given, it is imputed as 1. If the year of birth is missing or not given, it is imputed as the year of the screening interview minus the age in years provided by the respondent during the screening interview.

RIDAGEMN: The age in months, at the time of the screening interview, is provided for participants who are less than 80 years of age (RIDAGEYR<80). If the exact date of birth is not provided by the respondent, the age in months is calculated based on the imputed age in years at the time of the screening interview.

RIDAGEEX: The age in months, at the Mobile Examination Center (MEC) examination, is provided for participants under 80 years of age (RIDAGEEX<960).

RIDRETH1: This race/ethnicity variable was derived from responses to the survey questions on race and Hispanic origin. Respondents who self-identified as “Mexican American” were coded as such (i.e., RIDRETH1=1) regardless of their other race-ethnicity identities. Otherwise, self-identified “Hispanic” ethnicity would result in code “2, Other Hispanic” in the RIDRETH1 variable. All other non-Hispanic participants would then be categorized based on their self-reported races: non-Hispanic white (RIDRETH1=3), non-Hispanic black (RIDRETH1=4), and other non-Hispanic race including non-Hispanic multiracial (RIDRETH1=5).

RIDRETH1 is the only race/ethnicity variable in the 2009-2010 Demographics data file. The Demographics files that were released for NHANES 1999-2004 had a variable called ‘RIDRETH2’ that provided an analytic link to the NHANES III race/ethnicity variable. RIDRETH2 is not included in the NHANES 2009-2010 Demographics file.

DMDBORN2: Country of birth was recoded into five categories: 1) Born in 50 US states or Washington, DC; 2) Born in Mexico; 3) Born elsewhere; 4) Born in other Spanish speaking country (not Mexico); and 5) Born in other non-Spanish speaking country.

Note: Category 3 is not included in the current dataset, it is a place holder to combine across earlier years. Category 3 was only used for data from the 1999-2006 survey cycles. Please see below the Analytic Notes section for more information on combining this variable from multiple 2-year NHANES cycles.

DMDCITZN: Citizenship status is reported using two codes: 1) Citizen by birth or naturalization or 2) Not a citizen of the U.S. Persons who were born in the U.S. or U.S. territories who acquire citizenship at birth were coded as U.S. citizens.

DMDMARTL: The marital status question was asked of persons 14 years of age and older. Due to disclosure risks, marital status will only be released for persons 20 years of age and older.

RIDEXPRG: Pregnancy status at the time of the health examination was ascertained for females 8–59 years of age. Due to disclosure risks pregnancy status will only be released for women 20-44 years of age. The information used to code RIDEXPRG values included urine pregnancy test results and self-reported pregnancy status. Urine pregnancy tests were performed prior to the dual energy x-ray absorptiometry (DXA) exam. Persons who reported they were pregnant at the time of exam were assumed to be pregnant. As a result, if the urine test was negative, but the subject reported they were pregnant, the status was coded as ‘pregnant at exam’ (RIDEXPRG = 1). If the urine pregnancy results were negative and the respondent stated that they were not pregnant, the respondent was coded ‘not pregnant at exam’ (RIDEXPRG = 2). If the urine pregnancy results were negative and the respondent did not know her pregnancy status, the respondent was coded ’could not be determined’ (RIDEXPRG=3). Persons who were interviewed, but not examined also have an RIDEXPRG value = 3 (could not be determined). 

DMDYRSUS: This variable is the number of years the participant has lived in the United States. Participants who were born outside the U.S. were asked the month and year when they came to the U.S. to stay (DMQ.160). A small number of records were imputed because the participant did not report the month of their arrival. A month value of 7 (July) was used to impute DMDYRSUS for these respondents. The responses to the question were recoded into 9 categories ranging from less than one year to 50 years or more.

DMDFMSIZ: This variable is the number of people in the participant’s family. The definition of family is based on the Current Population Survey (CPS) criteria. The CPS defines a family as “a group of two people or more (one of whom is the householder) related by birth, marriage, or adoption and residing together”; all such people (including related subfamily members) are considered to be members of one family. Due to disclosure concerns, families that are comprised of 7 or more people are included the category that is labeled ‘7 or more’.

DMDHHSIZ: This variable is the number of people in the participant’s household. The values for this variable range from 1 to 7.  Due to disclosure concerns, households that are comprised of 7 or more people are included the category that is labeled ‘7 or more’.

DMDEDUC3: This variable provides information on the highest grade or level of education completed by participants 6-19 years of age. The responses were re-coded as follows: single years of education (grades 1-12), high school graduate/GED, and post-high school. Codes “55” (less than 5^th grade) and “66” (less than 9^th grade) were used to categorize older youth who had very low education levels.

DMDEDUC2: This variable is the highest grade or level of education completed by adults 20 years and older. The response categories are: less than 9^th grade education, 9-11th grade education (includes 12th grade and no diploma), High school graduate/GED, some college or associates (AA) degree, and college graduate or higher.

DMDSCHOL: This variable is the school attendance status. It is asked for participants 6-19 years of age.

DMQMILIT: This variable provides information on veteran’s/military status. Veterans include persons who served in the armed forces of the United States, specifically, the U.S. Army, Navy, Air Force, Marine Corps, and Coast Guard.

INDFMIN2: This variable is the total family income variable and is released as an income range value. NCHS used the U.S. Bureau of the Census Current Population Survey definition of “family” to group household members into one or more families (U.S. Census Bureau, 2008). The CPS defines a family as “a group of two people or more (one of whom is the householder) related by birth, marriage, or adoption and residing together”; all such people (including related subfamily members) are considered to be members of one family.

The income section of the household interview includes several questions about sources of income including wages, retirement income, disability payments, interest income, and assistance programs, but the amounts of income from each of the income sources were not obtained. The respondent was asked to report total family income for themselves and the other members of their family in dollars (question INQ200). If the respondent refused to answer INQ200 or did not know the total combined family income, an income screener question was asked (question INQ220) to query if the total family income was < $20,000 or ≥ $20,000. If the respondent answered INQ220, a follow-up question asked the respondent to select an income range (question INQ230) from a list of income ranges listed on a printed hand card; the midpoint of the income range value was used as the total family income value.

Family income was used to calculate the ratio of income to poverty (INDFMPIR) and estimated total household income (INDHHIN2).

INDHHIN2: This variable is the estimated total household income. If a household was comprised of a single CPS family, the family income value was used, as previously described. When more than one CPS family resided in the household, two methods were used to compute the estimated total household income. The preferred method was to use income data reported by each CPS family that was interviewed (INQ200). A second method was used, with multi-family households, in which the total household income information (INQ200) was asked of the household reference person.

When income information was obtained from all of the CPS families in a household, the reported CPS family income values were summed to compute total household income (INDHHIN2). When information was missing for any of the CPS families in the household, the estimated household income value, provided by a household reference person, was used to compute estimated total household income.

INDFMPIR: This variable is an index for the ratio of family income to poverty. The Department of Health and Human Services’ (HHS) poverty guidelines were used as the poverty measure to calculate this index. These guidelines are issued each year, in the Federal Register, for determining financial eligibility for certain federal programs such as Head Start, Supplemental Nutrition Assistance Program (SNAP) (formerly Food Stamp Program), Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), and the National School Lunch Program.

The variable INDFMPIR was calculated by dividing family income (INDFMIN2) by the poverty guidelines, specific to family size, as well as the appropriate year and state. The values were not computed if the income screener information (INQ 220: < $20,000 or ≥ $20,000) was the only family income information reported. If family income was reported as a range value, the midpoint of the range was used to compute the variable. Values at or above 5.00 were coded as 5.00 or more because of disclosure concerns. The values were not computed if the family income data was missing.

Household Reference Person: The household reference person is defined as the first household member 18 years of age or older listed on the household member roster, who owns or rents the residence where members of the household reside. The household reference person is comparable to “family reference person” in previous NHANES. Analysts frequently use information about the reference persons to characterize the socioeconomic status of the households where survey participants reside. The Demographics file includes information on the household reference person’s gender (DMDHRGND), age (DMDHRAGE), country of birth (DMDHRBRN), education level (DMDHREDU), and marital status (DMDHRMAR). Additionally, information on the education level of the household reference person’s spouse is included (DMDHSEDU).

SIALANG: This variable indicates the language used during the Sample Person Questionnaire interview conducted at the participant’s home.

SIAPROXY: This variable denotes whether a proxy respondent was used during the Sample Person Questionnaire interview.

SIAINTRP: This variable denotes whether an interpreter was used during the Sample Person Questionnaire interview. The language spoken by the respondent is not reported.

FIALANG: This variable indicates the language used during the Family Questionnaire interview conducted at the participant’s home.

FIAPROXY: This variable denotes whether a proxy respondent was used to complete the Family Questionnaire interview.

FIAINTRP: This variable denotes whether an interpreter was used to complete the Family Questionnaire interview. The language spoken by the respondent is not reported.

MIALANG: This variable indicates the language used for the computer-assisted personal interviewing (CAPI) portion of the Mobile Examination Center (MEC) interview.

MIAPROXY: This variable denotes whether a proxy respondent was used during the CAPI portion of the MEC interview

MIAINTRP: This variable denotes whether an interpreter was used during the CAPI portion of the MEC interview. The language spoken by the respondent is not reported.

AIALANG: This variable indicates the language used for the audio-computer-assisted self interview (ACASI) portion of the MEC interview.

Analytic Notes

Starting in 2007, a new sample design was implemented. All Hispanics were oversampled, not just Mexican Americans. 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. This has led to an increase in the number of participants aged 40+ and a decrease in 12-19 year olds when compared to domains in previous cycles. Lastly, pregnant women were no longer oversampled. Based on these changes, unweighted frequencies of certain variables may differ slightly in this survey cycle compared to survey cycles prior to 2007. For more details on the sample design, refer to the NHANES 2009 - 2010 Public Data General Release File Documentation, available on the NHANES website at: https://wwwn.cdc.gov/nchs/nhanes/continuousnhanes/default.aspx?BeginYear=2009

Due to the differences in sample design between NHANES 2007-2010 and the earlier cycles of the continuous NHANES, data users should carefully consider the analytic implications if these data are combined with data from earlier survey cycles. Please refer to the “Analytic Note Regarding 2007-2010 Survey Design Changes and Combining Data Across other Survey Cycles” (https://wwwn.cdc.gov/nchs/data/nhanes/2007-2008/analyticnote_2007-2010.pdf) for more detailed guidance on this issue.

DMDMARTL: Given the sample design changes starting in 2007, for 2009-2010 we are releasing marital status only for persons 20 years of age and older because of potential disclosure risks. Prior to 2007, marital status was released for participants aged 14 and older. The number of married persons aged 14-19 is less than 1%.

RIDEXPRG: Due to sample design changes starting in 2007, pregnant women and individuals 12-19 years old were no longer oversampled in 2009-2010. This change, combined with the noted age domain changes already mentioned, reduced the number of pregnant women ages 8-19 and 45-59. Because of possible disclosure risks in this release, we are only releasing pregnancy status for women 20-44. The percent of pregnant women/girls aged 8-19 is less than 2%. The percent of pregnant women aged 45-59 is less than 0.3%.

Country of Birth: For this variable the categories 4 (Born in other Spanish speaking country (not Mexico)) and 5 (Born in other non-Spanish speaking country) include U.S. territories.

Analysts who wish to include country of birth information in analyses that use multiple 2-year NHANES cycles, may recode DMDBORN2 to create the country of birth variable that was released with the NHANES 1999-2006 data (variable name: DMDBORN) using the following programming code:

          If (sddsrvyr=5) then do;
                 If dmdborn2 in (4,5) then dmdborn=3;
                 Else dmdborn=dmdborn2;
          End;
 

This same code can also be used for Household reference person country of birth variables DMDHRBR2 and DMDHRBRN.

Household Income: Analysts who wish to include household income information in analyses that use multiple 2-year NHANES cycles, may recode INDHHIN2 to create the household income variable that was released with the NHANES 1999-2006 data (variable name: INDHHINC) using the following programming code:

          If (sddsrvyr=5) then do;
                 If indhhin2 in (14,15) then indhhinc=11; 
                 Else indhhinc=indhhin2; 
          End; 

This same code can also be used for family income variables INDFMIN2 and INDFMINC.

Masked Variance Units (MVUs): Fifteen masked variance strata and 31 masked primary sampling units (PSUs) are included in the 2009-2010 NHANES Demographics data file. Fourteen strata have 2 PSUs and one stratum has 3 PSUs. These MVUs are a collection of secondary sampling units that are aggregated into groups for the purpose of variance estimation. The variance estimates that are produced, using the MVUs, closely approximate the variances that would have been estimated using the “true” sample design variance units that are based on the actual survey sample strata and primary sampling units.  MVUs are used to protect the confidentiality of information provided by survey participants and to reduce disclosure risks. The use of MVUs is described in the NHANES Analytic Guidelines. Analysts should review the Guidelines carefully prior to analyzing the survey data.

Sample Weights: The 2-year sample weights (WTINT2YR, WTMEC2YR) should be used for all NHANES 2009–2010 analyses. There are no 4-year weights in this file. The 4-year weights were only provided with the NHANES 2001–2002 release file. Detailed instructions for combining earlier datasets (1999–2000, 2001–2002, 2003-2004, 2005-2006 and 2007-2008) are provided in the “Analytic Note Regarding 2007-2010 Survey Design Changes and Combining Data Across other Survey Cycles”.

Please refer to the NHANES Analytic Guidelines (https://wwwn.cdc.gov/nchs/nhanes/analyticguidelines.aspx) and the on-line NHANES Tutorial (https://www.cdc.gov/nchs/tutorials/) for further details on the use of sample weights and other analytic issues.

References

• U.S. Department of Health & Human Services. Poverty Guidelines, Research, and Measurement. Washington, DC: U.S. Department of Health & Human Services, January 2011. http://aspe.hhs.gov/POVERTY/

Codebook and Frequencies