• 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 - Recode
  • RIDAGEEX - Exam Age in Months - Recode
  • RIDRETH1 - Race/Ethnicity - Recode
  • RIDRETH2 - Linked NH3 Race/Ethnicity - Recode
  • DMQMILIT - Veteran/Military Status
  • DMDBORN - 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+
  • DMDEDUC - Education - Recode (old version)
  • DMDSCHOL - Now attending school?
  • DMDMARTL - Marital Status
  • DMDHHSIZ - Total number of people in the Household
  • INDHHINC - Annual Household Income
  • INDFMINC - Annual Family Income
  • INDFMPIR - Family PIR
  • RIDEXPRG - Pregnancy Status at Exam - Recode
  • RIDPREG - Pregnancy Status - Recode (old version)
  • DMDHRGND - HH Ref Person Gender
  • DMDHRAGE - HH Ref Person Age
  • DMDHRBRN - 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
  • WTINT2YR - Full Sample 2 Year Interview Weight
  • WTINT4YR - Full Sample 4 Year Interview Weight
  • WTMEC2YR - Full Sample 2 Year MEC Exam Weight
  • WTMEC4YR - Full Sample 4 Year MEC Exam Weight
  • SDMVPSU - Masked Variance Pseudo-PSU
  • SDMVSTRA - Masked Variance Pseudo-Stratum
  • SDJ1REPN - Jack Knife Replicate Number
  • DMAETHN - Logical Imputation Flag for Ethnicity
  • DMARACE - Logical Imputation Flag for Race Recode
  • WTMREP01 - MEC Exam Weight Jack Knife Replicate 01
  • WTMREP02 - MEC Exam Weight Jack Knife Replicate 02
  • WTMREP03 - MEC Exam Weight Jack Knife Replicate 03
  • WTMREP04 - MEC Exam Weight Jack Knife Replicate 04
  • WTMREP05 - MEC Exam Weight Jack Knife Replicate 05
  • WTMREP06 - MEC Exam Weight Jack Knife Replicate 06
  • WTMREP07 - MEC Exam Weight Jack Knife Replicate 07
  • WTMREP08 - MEC Exam Weight Jack Knife Replicate 08
  • WTMREP09 - MEC Exam Weight Jack Knife Replicate 09
  • WTMREP10 - MEC Exam Weight Jack Knife Replicate 10
  • WTMREP11 - MEC Exam Weight Jack Knife Replicate 11
  • WTMREP12 - MEC Exam Weight Jack Knife Replicate 12
  • WTMREP13 - MEC Exam Weight Jack Knife Replicate 13
  • WTMREP14 - MEC Exam Weight Jack Knife Replicate 14
  • WTMREP15 - MEC Exam Weight Jack Knife Replicate 15
  • WTMREP16 - MEC Exam Weight Jack Knife Replicate 16
  • WTMREP17 - MEC Exam Weight Jack Knife Replicate 17
  • WTMREP18 - MEC Exam Weight Jack Knife Replicate 18
  • WTMREP19 - MEC Exam Weight Jack Knife Replicate 19
  • WTMREP20 - MEC Exam Weight Jack Knife Replicate 20
  • WTMREP21 - MEC Exam Weight Jack Knife Replicate 21
  • WTMREP22 - MEC Exam Weight Jack Knife Replicate 22
  • WTMREP23 - MEC Exam Weight Jack Knife Replicate 23
  • WTMREP24 - MEC Exam Weight Jack Knife Replicate 24
  • WTMREP25 - MEC Exam Weight Jack Knife Replicate 25
  • WTMREP26 - MEC Exam Weight Jack Knife Replicate 26
  • WTMREP27 - MEC Exam Weight Jack Knife Replicate 27
  • WTMREP28 - MEC Exam Weight Jack Knife Replicate 28
  • WTMREP29 - MEC Exam Weight Jack Knife Replicate 29
  • WTMREP30 - MEC Exam Weight Jack Knife Replicate 30
  • WTMREP31 - MEC Exam Weight Jack Knife Replicate 31
  • WTMREP32 - MEC Exam Weight Jack Knife Replicate 32
  • WTMREP33 - MEC Exam Weight Jack Knife Replicate 33
  • WTMREP34 - MEC Exam Weight Jack Knife Replicate 34
  • WTMREP35 - MEC Exam Weight Jack Knife Replicate 35
  • WTMREP36 - MEC Exam Weight Jack Knife Replicate 36
  • WTMREP37 - MEC Exam Weight Jack Knife Replicate 37
  • WTMREP38 - MEC Exam Weight Jack Knife Replicate 38
  • WTMREP39 - MEC Exam Weight Jack Knife Replicate 39
  • WTMREP40 - MEC Exam Weight Jack Knife Replicate 40
  • WTMREP41 - MEC Exam Weight Jack Knife Replicate 41
  • WTMREP42 - MEC Exam Weight Jack Knife Replicate 42
  • WTMREP43 - MEC Exam Weight Jack Knife Replicate 43
  • WTMREP44 - MEC Exam Weight Jack Knife Replicate 44
  • WTMREP45 - MEC Exam Weight Jack Knife Replicate 45
  • WTMREP46 - MEC Exam Weight Jack Knife Replicate 46
  • WTMREP47 - MEC Exam Weight Jack Knife Replicate 47
  • WTMREP48 - MEC Exam Weight Jack Knife Replicate 48
  • WTMREP49 - MEC Exam Weight Jack Knife Replicate 49
  • WTMREP50 - MEC Exam Weight Jack Knife Replicate 50
  • WTMREP51 - MEC Exam Weight Jack Knife Replicate 51
  • WTMREP52 - MEC Exam Weight Jack Knife Replicate 52
  • WTIREP01 - Interview Weight Jack Knife Replicate 01
  • WTIREP02 - Interview Weight Jack Knife Replicate 02
  • WTIREP03 - Interview Weight Jack Knife Replicate 03
  • WTIREP04 - Interview Weight Jack Knife Replicate 04
  • WTIREP05 - Interview Weight Jack Knife Replicate 05
  • WTIREP06 - Interview Weight Jack Knife Replicate 06
  • WTIREP07 - Interview Weight Jack Knife Replicate 07
  • WTIREP08 - Interview Weight Jack Knife Replicate 08
  • WTIREP09 - Interview Weight Jack Knife Replicate 09
  • WTIREP10 - Interview Weight Jack Knife Replicate 10
  • WTIREP11 - Interview Weight Jack Knife Replicate 11
  • WTIREP12 - Interview Weight Jack Knife Replicate 12
  • WTIREP13 - Interview Weight Jack Knife Replicate 13
  • WTIREP14 - Interview Weight Jack Knife Replicate 14
  • WTIREP15 - Interview Weight Jack Knife Replicate 15
  • WTIREP16 - Interview Weight Jack Knife Replicate 16
  • WTIREP17 - Interview Weight Jack Knife Replicate 17
  • WTIREP18 - Interview Weight Jack Knife Replicate 18
  • WTIREP19 - Interview Weight Jack Knife Replicate 19
  • WTIREP20 - Interview Weight Jack Knife Replicate 20
  • WTIREP21 - Interview Weight Jack Knife Replicate 21
  • WTIREP22 - Interview Weight Jack Knife Replicate 22
  • WTIREP23 - Interview Weight Jack Knife Replicate 23
  • WTIREP24 - Interview Weight Jack Knife Replicate 24
  • WTIREP25 - Interview Weight Jack Knife Replicate 25
  • WTIREP26 - Interview Weight Jack Knife Replicate 26
  • WTIREP27 - Interview Weight Jack Knife Replicate 27
  • WTIREP28 - Interview Weight Jack Knife Replicate 28
  • WTIREP29 - Interview Weight Jack Knife Replicate 29
  • WTIREP30 - Interview Weight Jack Knife Replicate 30
  • WTIREP31 - Interview Weight Jack Knife Replicate 31
  • WTIREP32 - Interview Weight Jack Knife Replicate 32
  • WTIREP33 - Interview Weight Jack Knife Replicate 33
  • WTIREP34 - Interview Weight Jack Knife Replicate 34
  • WTIREP35 - Interview Weight Jack Knife Replicate 35
  • WTIREP36 - Interview Weight Jack Knife Replicate 36
  • WTIREP37 - Interview Weight Jack Knife Replicate 37
  • WTIREP38 - Interview Weight Jack Knife Replicate 38
  • WTIREP39 - Interview Weight Jack Knife Replicate 39
  • WTIREP40 - Interview Weight Jack Knife Replicate 40
  • WTIREP41 - Interview Weight Jack Knife Replicate 41
  • WTIREP42 - Interview Weight Jack Knife Replicate 42
  • WTIREP43 - Interview Weight Jack Knife Replicate 43
  • WTIREP44 - Interview Weight Jack Knife Replicate 44
  • WTIREP45 - Interview Weight Jack Knife Replicate 45
  • WTIREP46 - Interview Weight Jack Knife Replicate 46
  • WTIREP47 - Interview Weight Jack Knife Replicate 47
  • WTIREP48 - Interview Weight Jack Knife Replicate 48
  • WTIREP49 - Interview Weight Jack Knife Replicate 49
  • WTIREP50 - Interview Weight Jack Knife Replicate 50
  • WTIREP51 - Interview Weight Jack Knife Replicate 51
  • WTIREP52 - Interview Weight Jack Knife Replicate 52

National Health and Nutrition Examination Survey

1999-2000 Data Documentation, Codebook, and Frequencies

Demographic Variables & Sample Weights (DEMO)

Data File: DEMO.xpt

First Published: June 2002

Last Revised: September 2009

Component Description

The NHANES 1999-2000 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.

Eligible Sample

All survey participants who have a household interview record have a Demographics file record. The Demographics questionnaire items include family-level and individual-level information. The target age groups for the Demographics questions vary. Please review the NHANES 1999-2000 Family and Sample Person Demographics section questionnaires and codebooks carefully to review the content of the Demographic file and determine the target age groups for the questionnaire items.

Interview Setting and Mode of Administration

Demographics information was collected in the home prior to the health examination. Computer-assisted personal interviewing (CAPI) methodology was used. Persons 16 years of age and older and emancipated minors were interviewed directly. A proxy provided information for survey participants who were less than 16 years of age and for individuals who could not answer the questions themselves.

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. 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 information was recorded that was inconsistent with previous data entries or respondent characteristics such as the respondent’s age. Questionnaire “skip” patterns were pre-programmed in the questionnaires 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 several interviews 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 posted on the NHANES website.

Data Processing and Editing

SDDSRVYR represents the data release number. A code of ‘1’ denotes the NHANES 1999-2000 data release cycle.

RIDSTATR is a recoded variable representing interview and examination status. The status codes for a small number of sample persons who were interviewed in their homes, but not examined, were recoded and these individuals are included in the “interviewed only” category.

RIDEXMON is a variable indicating 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: This is the age of the sample person at the time of the screening interview. Age in years is reported by single year of age for persons from 1 through 84 years of age. For older adults, age in years was top coded at 85 years to reduce the risk of disclosure. All adults 85 years and older have a RIDAGEYR value of ’85’. In NHANES 1999-2000, the weighted mean age for participants 85 years and older is 88 years.

If exact date of birth information is provided during the interview, this information is used to calculate the exact age on the date of screening. Otherwise, an imputed date of birth is created using the following procedures: When date of birth information is missing or refused, but age in years is provided by the sample person: If month of birth is missing or not given it is imputed as 7. If day of birth is missing or not given, it is imputed as 1. If year of birth is missing or not given, it is imputed as the year of the screening interview less the age in years provided by the sample person at screening. Corrections are made to this imputed information for sample persons who are less than 1 year of age at the time of screening.

RIDAGEMN is age in months at household screening, provided only for those who were less than 85 years of age. If exact date of birth is not provided by the sample person, then the age in months is calculated based on the imputed age at screener to allow the sample person to proceed with the questionnaire and examination.

RIDAGEEX is age in months at MEC examination, provided only for those who were less than 85 years of age (RIDAGEYR < 85) at the time of the household screening interview. RIDAGEEX was not calculated for individuals with an imputed age.

RIDRETH1: This race/ethnicity variable is derived by combining responses to 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).

RIDRETH2 is the race/ethnicity recode that can be linked to the NHANES III race/ethnicity variable. Non-Hispanics who indicated more than one race (multiracial) and then selected a main race as black (non-Hispanic) or white (non-Hispanic) were recoded into those respective categories. In other cases, the coding was similar to RIDRETH1.

DMDBORN: Country of birth was recoded into three categories: 1) born in 50 U.S. states or Washington, D.C.; 2) born in Mexico; and 3) born in any other location or foreign country.

INDFMINC: This variable is the total family income variable. NCHS used the U.S. Bureau of the Census Current Population Survey (CPS) definition of “family” to group household members into one or more families (US Census, 2003). 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. Over eighty percent of the NHANES households were single-family households; the remaining households were comprised of 2 or more CPS families.

After the information about sources of income was obtained in the Family Interview Income section questionnaire (INQ), the respondent was asked to report the total combined 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 was then used as the total family income value. Family income values were used to calculate the ratio of income to poverty (INDFMPIR) and estimated total household income (INDHHINC) as described below. Total family income is reported as a range in the NHANES data file.

INDHHINC: This variable is the estimated total household income. The estimated household income was derived from family income data. 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 estimated total household income. One method was to use income data reported by each CPS family that was interviewed (INQ200). The second method for multi-family households used total household income information (INQ200) provided by a household reference person. The income information provided by respondents for each CPS family (method 1) was used whenever possible because this information was considered to be more reliable than information provided by a household reference person who may or may not have had firsthand knowledge of the total household income.

When income information was obtained from each of the CPS families in a household, the reported CPS family income values were summed to compute total household income (INDHHINC). When information was missing for any of the CPS families in the household, the estimated household income value provided by a family reference person was used to compute estimated total household income. Total household income could not be calculated for multi-family households when income range data were reported by any of the families in the household and thus the household income data are coded as missing.

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 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.

DMDMARTL is the derived marital status variable. Marital status data were collected for sample persons 14 years of age and older. Individuals belonging to single person households were not asked about their marital status during part of the 1999-2000 data collection cycle. For a number of these persons marital status was imputed from other questionnaire items that made reference to their marital status. Marital status remains missing for 566 sample persons 14 years of age and older due to lack of sufficient data for imputation.

PREGNANCY STATUS: Pregnancy status at the time of examination (RIDEXPRG) is reported for females 8-59 years of age. Females 8-59 years of age received a urine pregnancy test 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; if the urine test was negative, but the subject reported they were pregnant, the status was still coded as pregnant at exam (RIDEXPRG=1). If the urine pregnancy results were negative and the respondent said they were not pregnant, the respondent was coded not pregnant at examination (RIDEXPRG=2). Persons who were only interviewed have an RIDEXPRG value = 3 (could not be determined).

Note: The pregnancy recode variable previously released with NHANES 1999-2000 was called RIDPREG. RIDPREG was created to allow analysts to exclude pregnant women from analyses; this determination was based on the most comprehensive information available at the time of data release. RIDPREG was a more conservative indicator of pregnancy status, and was derived using several sources of information. For subjects who were only interviewed, pregnancy status at the time of survey screening, and menstrual status were used to determine possible pregnancy status. For examined individuals, if an individual indicated that they were pregnant during the reproductive health questionnaire (RHQ), or reported they were pregnant in the shared exclusion questions (SEQ), or had a positive urine pregnancy test, these individuals were determined to be pregnant. If an individual was screened as pregnant and had other information which supported the information in the reproductive health questionnaire (RHQ), they were determined to be pregnant. If an individual indicated that they were not pregnant and also had a negative urine pregnancy test, they were determined to not be pregnant. It has been determined that a variable indicating pregnancy status at exam (RIDEXPRG) is a more useful analytic variable rather than the more conservative RIDPREG. Approximately 20-25 individuals in the NHANES 1999-2000 sample could have different pregnancy status values using the RIDEXPRG and RIDPREG algorithms.

The following new variables are included in this updated NHANES 1999-2000 Demographic file:

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 US  territories who acquire citizenship at birth were coded as US citizens.

DMDYRSUS: This variable is the number of years the respondent has lived in the United States. Respondents who were born outside the U.S. were asked the month and year when they came to the U.S. to stay (DMQ.160). The responses to the question were recoded into 9 categories ranging from less than one year to 50 years or more.

DMDHHSIZ: This variable is the number of people in the respondent’s household. The values for this variable range from 1 to 7 with 7 being the code used for households comprised of 7 or more members.

DMDEDUC3: This variable provides information on the highest grade or level of education completed by respondents 6-19 years of age. The responses were recoded by NCHS as follows: single years of education (grades 1-12), high school graduate/GED, and post-high school.

DMDEDUC2: This variable is the highest grade or level of education completed by adults 20 years of age and older. The response categories are: less than 9th 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. DMDEDUC2 provides more detailed information on education levels of adults compared to the categories that were previously released in the NHANES 1999-2000 Demographic file.

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

Analytic Notes

RIDRETH2 race/ethnicity recode should be used to compare NHANES 1999-2000 estimates of health measures with those of NHANES III.

After the original Demographic file was released, additional interview sections were recovered for 5 individuals that resulted in improved race/ethnicity information. As a result, both RIDRETH1 and RIDRETH2 have changed for individuals with SEQN 8239, 8270, 8463, 3578, 5343.

Income variables: Income information was not obtained from all of the families in the survey sample. Some respondents refused to provide this information and others had little or no knowledge of family income. No attempt was made to assign or impute income in these instances. Incomplete information was reported to the extent possible.

Educational attainment: Five educational attainment variables are included the Demographics File. Three of the education variables target survey participants. Two other education variables provide information about the educational attainment of the household reference person (DMDHREDU) and the household reference person’s spouse (DMDHSEDU), when applicable. A brief description of survey participant educational attainment variables follows.

DMDEDUC is a 3-category variable that groups survey participants 6 years of age and over into one of three educational attainment groups: 1) less than high school education attainment, 2) high school graduate (has a high school diploma or high school equivalency diploma such as a General Educational Development/GED), or 3) has more than a high school education.

In addition to DMDEDUC, the Demographics File contains 2 variables that provide additional information on the educational attainment level of survey participants. Educational attainment information for persons 6 through 19 years of age is included in DMDEDUC3. Detailed educational attainment information for adults who are 20 years of age and over is reported in DMDEDUC2.

Questionnaire section files, MEC examination files, and laboratory files can be linked to sample person demographics variables using the unique survey participant identifier SEQN. RIDSTATR provides the MEC examination status of a sample person.

The two-year sample weights (WTINT2YR, WTMEC2YR) should be used for NHANES 1999-2000 analyses and the four-year sample weights (WTINT4YR, WTMEC4YR) for combined analyses of NHANES 1999-2000 & NHANES 2001-2002 data. Please refer to the analytic guidelines and the on-line NHANES Tutorial  provided with the data release files to determine the appropriate analytic methodology for this dataset.  Both of these are available on the NHANES website.

References

• U.S. Census Bureau. Current Population Survey (CPS) Definitions and Explanations. 2003. http://www.census.gov/population/www/cps/cpsdef.html
• 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