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This study is maintained and distributed by the National Archive of Computerized Data on Aging (NACDA), the aging program within ICPSR. NACDA is sponsored by the National Institute on Aging (NIA) at the National Institutes of Heath (NIH).

National Health and Nutrition Examination Survey (NHANES), 1999-2000 (ICPSR 25501) RSS

Principal Investigator(s):

Summary:

The National Health and Nutrition Examination Surveys (NHANES) is a program of studies designed to assess the health and nutritional status of adults and children in the United States. The NHANES combines personal interviews and physical examinations, which focus on different population groups or health topics. These surveys have been conducted by the National Center for Health Statistics (NCHS) on a periodic basis from 1971 to 1994. In 1999 the NHANES became a continuous program with a changing focus on a variety of health and nutrition measurements which were designed to meet current and emerging concerns. The surveys examine a nationally representative sample of approximately 5,000 persons each year. These persons are located in counties across the United States, 15 of which are visited each year. The 1999-2000 NHANES contains data for 9,965 individuals (and MEC examined sample size of 9,282) of all ages. Many questions that were asked in NHANES II, 1976-1980, Hispanic HANES 1982-1984, and NHANES III, 1988-1994, were combined with new questions in the NHANES 1999-2000. The 1999-2000 NHANES collected data on the prevalence of selected chronic conditions and diseases in the population and estimates for previously undiagnosed conditions, as well as those known to and reported by respondents. Risk factors, those aspects of a person's lifestyle, constitution, heredity, or environment that may increase the chances of developing a certain disease or condition, were examined. Data on smoking, alcohol consumption, sexual practices, drug use, physical fitness and activity, weight, and dietary intake were collected. Information on certain aspects of reproductive health, such as use of oral contraceptives and breastfeeding practices, were also collected. The interview includes demographic, socioeconomic, dietary, and health-related questions. The examination component consists of medical, dental, and physiological measurements, as well as laboratory tests. Demographic data file variables are grouped into three broad categories: (1) Status Variables: Provide core information on the survey participant. Examples of the core variables include interview status, examination status, and sequence number. (Sequence number is a unique ID assigned to each sample person and is required to match the information on this demographic file to the rest of the NHANES 1999-2000 data). (2) Recoded Demographic Variables: The variables include age (age in months for persons through age 19 years, 11 months; age in years for 1-84 year olds, and a top-coded age group of 85+ years), gender, a race/ethnicity variable, an education variable (high school, and more than high school education), country of birth (United States, Mexico, or other foreign born), and pregnancy status variable. Some of the groupings were made due to limited sample sizes for the two-year dataset. (3) Interview and Examination Sample Weight Variables: Sample weights are available for analyzing NHANES 1999-2000 data. For a complete listing of survey contents for all years of the NHANES see the document -- Survey Content -- NHANES 1999-2010.

Series: National Health and Nutrition Examination Survey (NHANES) and Followup Series

Access Notes

  • These data are freely available.

Dataset(s)

WARNING: Because this study has many datasets, the download all files option has been suppressed, and you will need to download one dataset at a time.

WARNING: This study is over 150MB in size and may take several minutes to download on a typical internet connection.

DS11:  Examination: Audiometry (Subsample) - Download All Files (25,275 KB)
DS12:  Examination: Audiometry Tympanometry - Download All Files (26,392 KB)
DS13:  Examination: Balance (Subsample) - Download All Files (15,799 KB)
DS14:  Examination: Bioelectrical Impedance Analysis - Download All Files (56,815 KB)
DS15:  Examination: Blood Pressure - Download All Files (68,801 KB)
DS16:  Examination: Body Measures - Download All Files (71,139 KB)
DS17:  Examination: Cardiovascular Fitness - Download All Files (40,188 KB)
DS18:  Examination: Composite International Diagnostic Interview (Generalized Anxiety Disorder) (Subsample) - Download All Files (14,838 KB)
DS19:  Examination: Composite International Diagnostic Interview (Major Depression Module) (Subsample) - Download All Files (16,073 KB)
DS20:  Examination: Composite International Diagnostic Interview (Panic Disorder Module) (Subsample) - Download All Files (16,117 KB)
DS21:  Examination: Dietary Interview (Individual Foods File) - Download All Files (1,026,868 KB)
DS22:  Examination: Dietary Interview (Total Nutrients) - Download All Files (89,956 KB)
DS23:  Examination: Dual Energy X-Ray Absorptiometry (DXX) - Download All Files (298,270 KB)
DS24:  Examination: Dual Energy X-Ray Absorptiometry (DXX) -- Subset - Download All Files (10,434 KB)
DS25:  Examination: Lower Extremity Disease (Ankle Brachial Blood Pressure Index) - Download All Files (24,908 KB)
DS26:  Examination: Lower Extremity Disease (Peripheral Neuropathy) - Download All Files (25,675 KB)
DS27:  Examination: Muscular Strength - Download All Files (20,165 KB)
DS28:  Examination: Oral Health (Dentition) - Download All Files (83,748 KB)
DS29:  Examination: Oral Health (Periodontal Section) - Download All Files (63,864 KB)
DS30:  Examination: Oral Health (Referral) - Download All Files (63,052 KB)
DS31:  Examination: Shared Exclusion Questions - Download All Files (63,391 KB)
DS32:  Examination: Tuberculosis - Download All Files (63,351 KB)
DS33:  Examination: Vision Exam - Download All Files (56,159 KB)
DS102:  Laboratory: Surplus Sera Cystatin C - Download All Files (23,650 KB)
DS103:  Laboratory: Antibody to Cytomegalovirus IgG (Surplus Sera) - Download All Files (35,685 KB)
DS104:  Laboratory: Antibody to Human Herpes Virus 1 (Surplus Sera) - Download All Files (14,728 KB)
DS105:  Laboratory: Antibody to Mumps (Surplus Sera) - Download All Files (36,012 KB)
DS106:  Laboratory: Perfluorinated Chemicals (Surplus Sera) - Download All Files (16,596 KB)
DS107:  Laboratory: Varicella Zoster Virus Antibody (Surplus Sera) - Download All Files (7,242 KB)
DS108:  Laboratory: Serum Transferrin and Receptor (Surplus Sera) - Download All Files (7,368 KB)
DS109:  Laboratory: Phlebotomy - Download All Files (64,128 KB)
DS110:  Laboratory: Phpypa Urinary Phthalates (Subsample) - Download All Files (31,147 KB)
DS111:  Laboratory: Urine Collection (Pregnancy) - Download All Files (17,306 KB)
DS112:  Laboratory: Lab 02 Hepatitis B Surface Antibody - Download All Files (60,846 KB)
DS113:  Laboratory: Lab 02 Hepatitis - Download All Files (61,180 KB)
DS114:  Laboratory: Lab 02 Hepatitis A Antibody - Download All Files (60,853 KB)
DS115:  Laboratory: Lab 03 Human Immunodeficiency Virus - Download All Files (23,778 KB)
DS116:  Laboratory: Lab 04 Volatile Organic Compounds in Blood and Water - Download All Files (12,009 KB)
DS117:  Laboratory: Lab 05 Chlamydia and Gonorrhea - Download All Files (19,043 KB)
DS118:  Laboratory: Lab 06 Nutritional Biochemistries - Download All Files (71,346 KB)
DS119:  Laboratory: Lab 06Hm Heavy Metals (Subsample) - Download All Files (29,925 KB)
DS120:  Laboratory: Lab 07 Latex - Download All Files (38,830 KB)
DS121:  Laboratory: Lab 09 Herpes I and II - Download All Files (31,073 KB)
DS122:  Laboratory: Lab 10 Glycohemoglobin - Download All Files (49,165 KB)
DS123:  Laboratory: Lab 10Am Plasma Glucose (Subsample) - Download All Files (27,400 KB)
DS124:  Laboratory: Lab 11 C Reactive Protein - Download All Files (60,417 KB)
DS125:  Laboratory: Lab 13 Total Cholesterol - Download All Files (59,976 KB)
DS126:  Laboratory: Lab 13Am Triglycerides (Subsample) - Download All Files (31,442 KB)
DS127:  Laboratory: Lab 16 Urinary Albumin and Creatinine - Download All Files (56,571 KB)
DS128:  Laboratory: Lab 17 Cryptosporidum and Toxoplasma - Download All Files (42,629 KB)
DS129:  Laboratory: Lab 18 Biochemistry Profile and Hormones - Download All Files (55,967 KB)
DS130:  Laboratory: Lab 18T4 Thyroid Stimulating Hormone and Thyroxine (Subsample) - Download All Files (20,600 KB)
DS131:  Laboratory: Lab 19 Measles Rubella and Varicella - Download All Files (42,303 KB)
DS132:  Laboratory: Lab 20 Lead Dust - Download All Files (12,802 KB)
DS133:  Laboratory: Lab 21 Volatile Organic Compounds (Subsample) - Download All Files (12,271 KB)
DS134:  Laboratory: Lab 22 Hair Mercury - Download All Files (23,970 KB)
DS135:  Laboratory: Lab 25 Complete Blood Count - Download All Files (67,054 KB)
DS136:  Laboratory: Lab 26 Pesticides (Subsample) - Download All Files (27,712 KB)
DS137:  Laboratory: Lab 28 Dioxins (Subsample) - Download All Files (35,125 KB)
DS201:  Questionnaire: Acculturation - Download All Files (52,690 KB)
DS202:  Questionnaire: Alcohol Use - Download All Files (34,790 KB)
DS203:  Questionnaire: Audiometry - Download All Files (67,050 KB)
DS204:  Questionnaire: Balance - Download All Files (26,685 KB)
DS205:  Questionnaire: Blood Pressure - Download All Files (46,372 KB)
DS206:  Questionnaire: Cardiovascular Disease and Health - Download All Files (26,115 KB)
DS207:  Questionnaire: Cognitive Functioning - Download All Files (17,452 KB)
DS208:  Questionnaire: Current Health Status - Download All Files (63,249 KB)
DS209:  Questionnaire: Dermatology - Download All Files (65,773 KB)
DS210:  Questionnaire: Diabetes - Download All Files (67,584 KB)
DS211:  Questionnaire: Diet Behavior and Alcohol Consumption - Download All Files (74,504 KB)
DS212:  Questionnaire: Dietary Supplement Use -- Supplement Counts - Download All Files (69,202 KB)
DS213:  Questionnaire: Dietary Supplement Use -- Participants Use of Supplement - Download All Files (56,198 KB)
DS214:  Questionnaire: Dietary Supplement Use -- Supplement Information - Download All Files (6,578 KB)
DS215:  Questionnaire: Dietary Supplement Use -- Ingredient Information - Download All Files (10,791 KB)
DS216:  Questionnaire: Dietary Supplement Use -- Supplement Blend - Download All Files (6,027 KB)
DS217:  Questionnaire: Drug Use - Download All Files (24,150 KB)
DS218:  Questionnaire: Early Childhood - Download All Files (31,330 KB)
DS219:  Questionnaire: Family Smoking - Download All Files (69,643 KB)
DS220:  Questionnaire: Food Security - Download All Files (70,541 KB)
DS221:  Questionnaire: Health Insurance - Download All Files (69,813 KB)
DS222:  Questionnaire: Hospital Utilization - Download All Files (69,791 KB)
DS223:  Questionnaire: Housing Characteristics - Download All Files (70,659 KB)
DS224:  Questionnaire: Immunization - Download All Files (69,064 KB)
DS225:  Questionnaire: Kidney Conditions - Download All Files (37,657 KB)
DS226:  Questionnaire: Medical Conditions - Download All Files (85,262 KB)
DS227:  Questionnaire: Miscellaneous Pain - Download All Files (39,882 KB)
DS228:  Questionnaire: Occupation - Download All Files (54,859 KB)
DS229:  Questionnaire: Oral Health - Download All Files (65,606 KB)
DS230:  Questionnaire: Osteoporosis - Download All Files (39,973 KB)
DS231:  Questionnaire: Analgesics Pain Relievers - Download All Files (38,071 KB)
DS232:  Questionnaire: Pesticide Use - Download All Files (70,245 KB)
DS233:  Questionnaire: Physical Activity - Download All Files (66,410 KB)
DS234:  Questionnaire: Physical Activity Individual Activities File - Download All Files (65,463 KB)
DS235:  Questionnaire: Physical Functioning - Download All Files (75,769 KB)
DS236:  Questionnaire: Prescription Medications - Download All Files (112,308 KB)
DS237:  Questionnaire: Drug Information - Download All Files (11,775 KB)
DS238:  Questionnaire: Reproductive Health - Download All Files (33,183 KB)
DS239:  Questionnaire: Respiratory Health - Download All Files (67,820 KB)
DS240:  Questionnaire: Sexual Behavior - Download All Files (24,733 KB)
DS241:  Questionnaire: Smoking and Tobacco Use (MEC) - Download All Files (52,548 KB)
DS242:  Questionnaire: Smoking and Tobacco Use - Download All Files (39,453 KB)
DS243:  Questionnaire: Social Support - Download All Files (17,669 KB)
DS244:  Questionnaire: Tuberculosis - Download All Files (66,398 KB)
DS245:  Questionnaire: Vision - Download All Files (21,338 KB)
DS246:  Questionnaire: Weight History - Download All Files (47,410 KB)

Study Description

Citation

United States Department of Health and Human Services. Centers for Disease Control and Prevention. National Center for Health Statistics. National Health and Nutrition Examination Survey (NHANES), 1999-2000. ICPSR25501-v4. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 2012-02-22. doi:10.3886/ICPSR25501.v4

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Scope of Study

Subject Terms:   acculturation, aging, alcohol consumption, allergies, anxiety, cardiovascular disease, cognitive functioning, consumer behavior, demographic characteristics, depression (psychology), diabetes, diet, disease, drug use, emotional states, emotional support, ethnicity, eyesight, health behavior, health care, health insurance, health services utilization, health status, hearing (physiology), hospitalization, illness, immunization, income, malnutrition, medical evaluation, mental health, nutrition, occupations, physical fitness, populations, pregnancy, prescription drugs, reproductive history, respiratory diseases, risk factors, sexual behavior, sleep disorders, smoking, social indicators, social support, treatment, tuberculosis, vaccines

Geographic Coverage:   United States

Time Period:  

  • 1999--2000

Date of Collection:  

  • 1999-03--2000-12

Unit of Observation:   individual

Universe:   The NHANES target population is the civilian, noninstitutionalized United States population.

Data Types:   clinical data, survey data

Data Collection Notes:

NCHS provides continuous updates/new data notification, as well as other important information for the NHANES. It is recommended that users of these data sign up for the information through the NHANES Listserv. The "What's New" page on the NHANES Web site provides updates/new information which may not be included in the listserv emails. Further, not all documentaion files are included with this ICPSR release and may be found at the NHANES 1999-2000 Web site.

In preparing the data files for this collection, the National Center for Health Statistics (NCHS) has removed direct identifiers and characteristics that might lead to identification of data subjects. As an additional precaution NCHS requires, under Section 308(d) of the Public Health Service Act (42 U.S.C. 242m), that data collected by NCHS not be used for any purpose other than statistical analysis and reporting. NCHS further requires that analysts not use the data to learn the identity of any persons or establishments and that the director of NCHS be notified if any identities are inadvertently discovered. ICPSR member institutions and other users ordering data from ICPSR are expected to adhere to these restrictions.

Many variables that are listed in the Demographic questionnaire sections of the Household Interview were omitted (by NCHS) from this data release due to concerns about participant confidentiality. NCHS did not include confidential and administrative data in this release and further, some variables have been recoded or top-coded to protect the confidentiality of survey participants.

Many of the NHANES 1999-2000 questions were also asked in NHANES II, 1976-1980, Hispanic HANES 1982-1984, and NHANES III, 1988-1994. New questions were added to the survey based on recommendations from survey collaborators, NCHS staff, and other interagency work groups.

NHANES 1999-2000 survey design and demographic variables are found in Part 1 Demographics file in this release. All of the data files can be linked by using the common survey participant identification number (variable name: SEQN). Merging information from multiple NHANES 1999-2000 data files using SEQN ensures that the appropriate information for each survey participant is linked correctly. All data files should be sorted by SEQN.

The NHANES 1999-2000 data files do not have the same number of records in each file. For example, there are different numbers of subjects in the Interview and Examination samples of the Survey. Additionally, the number of records in each data file varies depending on gender and age profiles for the specific component(s).

The sample person demographic file is composed of a limited set of core variables that are required to analyze NHANES 1999-2000 data.

Per agreement with the National Center for Health Statistics (NCHS), ICPSR distributes the data file(s) and text of the technical documentation for this collection as prepared by NCHS.

All data files have been merged with the demographics file with the exception of those parts that did not contain the linking variable SEQN, which are as follows: Questionnaire: Dietary Supplement Use -- Supplement Information (Part 214), Questionnaire: Dietary Supplement Use -- Ingredient Information (Part 215), Questionnaire: Dietary Supplement Use -- Supplement Blend (Part 216), and Questionnaire: Drug Information (Part 237).

Within the Oral Health (Dentition) File Part 28 variables "OHX02CSC through OHX15CSC and OHX18CSC through OHX31CSC, as well as OHX02SE, OHX03SE, OHX14SE, OHX15SE, OHX18SE, OHX19SE, OHX30SE, and OHX31SE" the NCHS coded multiple conditions per record. Users should consult the documentation and review the labeling of the variables in question for further information.

The Jackknife weight variables have been included in this dataset. Users shoud not attempt analyses with the Jackknife weight variables in SDA before consulting the documentation made available through ICPSR and more extensive documentation on the NHANES website.

All missing values that had been coded -99 within the data, have been recoded to "System Missing" in order to provide consistency between the other respective NHANES studies. (25502, 25503, 25504, 25505)

The user guides that are presently available are comprised of documentation from the NCHS. These user guides do not reflect the merging of each file with the demographics file, as this was done by ICPSR staff.

Methodology

Study Design:  

The most recent NHANES began in 1999. Every year, approximately 7,000 individuals, of all ages, are interviewed in their homes and of these, approximately 5,000 complete the health examination component of the survey. A majority of the health examinations are conducted in mobile examination centers (MECs). The MECs provide an ideal setting for the collection of high quality data in a standardized environment. In addition to the MEC examinations, a small number of survey participants receive an abbreviated health examination in their homes if they are unable to come to the MEC. The NHANES target population is the civilian, noninstitutionalized United States population. NHANES 1999-2000 includes over-sampling of low-income persons, adolescents 12-19 years of age, persons 60+ years of age, African Americans and Mexican Americans. Initially, households are identified for inclusion in the NHANES sample and an advance letter is mailed to each address informing the occupant(s) that an NHANES interviewer will visit their home. The household interview component is comprised of Screener, Sample Person, and Family interviews, each of which has a separate questionnaire (please refer to the data file documentation). Trained household interviewers administer all of the questionnaires. In most cases, the interview setting was the survey participant's home. The interview data are recorded using the Blaise computer-assisted personal interview (CAPI) system. When the interviewer arrives at the home, he or she shows an official identification badge and briefly explains the purpose of the survey. If the occupant has not seen the advance letter, a copy is given to them to read. The interviewer requests that the occupant answer a brief questionnaire to determine if any household occupants are eligible to participate in NHANES. If eligible individuals are identified, the interviewer proceeds with efforts to recruit these individuals. Initially, the interviewer explains the household questionnaires to all eligible participants 16 years of age and older, informs the potential respondents of their rights, and provides assurances about the confidentiality of the survey data (reiterating what is stated in the advance letter). A majority of the household interviews are conducted during the first contact. If this is inconvenient for the survey participant, an appointment is made to administer the household interview questionnaires later. Household interviews for survey participants under 16 years of age are conducted with a proxy (usually their parent or guardian). If there is no one living in the household who is over 16, participants under 16 years of age are permitted to self-report. Respondents are asked to sign an Interview Consent Form agreeing to participate in the household interview portion of the survey. For participants 16-17 years of age a parent or guardian consents and the child gives his/her assent. After the household interview is completed, the interviewer reviews a second informed consent brochure with the participant. This brochure contains detailed information about the NHANES health examination component. All interviewed persons are asked to complete the health examination component. Those who agree to participate are asked to sign additional consent forms for the health examination component. The interviewer telephones the NHANES field office from the participant's home to schedule an appointment for the examination. The interviewer informs the participants that they will receive remuneration as well as reimbursement for transportation and childcare expenses, if necessary.

Target Populations

There are different target population groups for the topics within and between NHANES questionnaire sections. For example, in the Nutrition and Diet Behavior section, questions pertaining to infant nutrition and breast-feeding were asked of proxy respondents for children 6 years of age and younger, alcohol consumption frequency questions were asked of persons 20+ years of age, and senior meal program participation questions were asked of respondents 60+ years of age. Data users should review the survey questionnaire codebooks thoroughly to determine the target populations for each NHANES questionnaire section and sub-section.

The NHANES Health Examination Component

When a participant arrives at the MEC, the MEC Coordinator greets the participant and verifies all pertinent identifier information. The participant is given a disposable paper gown, a pair of slippers, and a urine specimen cup. MEC staff direct survey participants to the rooms where the examination components are conducted. Each MEC survey team consists of one physician, one dentist, two dietary interviewers, three certified medical technologists, five health technicians, one phlebotomist, two interviewers, and one computer data manager. Additionally, there is a person designated as the Coordinator who is responsible for managing the movement of participants between examinations, providing remuneration, and distributing a preliminary report of findings. Upon completion of the examination, each examinee is remunerated. Some of the medical findings of the examination are given to the examinees before they leave the MEC. The other reportable survey findings are mailed to participants after the laboratory assays and special tests are completed.

MEC Operations

Three MECs are equipped for use in NHANES. Each MEC consists of four large, inter-connected trailer units. An advance team sets up the MECs prior to the start of the survey examinations. Water, sewer, electrical, and communication lines are connected during set-up. The MEC equipment and data collection systems must be checked and calibrated prior to the start of survey data collection. The MECs are open a total of five days per week, and the nonoperational days change on a rotating basis so that appointments can be scheduled on any day of the week. Two examination sessions are conducted daily. For the convenience of the survey participants, appointments can be scheduled during morning, afternoon, or evening hours. The examinations require up to three hours to complete. At any given time during the survey, examinations are conducted at two survey locations simultaneously. Staff vacations are scheduled for periods of about one month at New Years and about two weeks during the summer, leaving ten and one-half months to conduct examinations.

Second Day Examinations and Dietary Interviews

Second day (i.e., repeat) MEC examinations were pilot tested in 1999 and implemented in 2000. Approximately 5 percent of examined persons over 20 years of age from each survey location were asked to complete second day exams. Second day dietary interviews were completed on ten percent of all examined persons in 2000. The second day dietary interview is a primary data collection technique to improve the estimation of distributions of nutrient intakes. Second day examination and dietary data are not included in this data file.

Home Examinations

Participants under 1 year of age or 60+ years of age, who are unable or unwilling to come to the MEC for an examination, are eligible to receive a home examination. Home examination data are not included in this data file.

Sample:   The NHANES survey design is a stratified, multistage probability sample of the civilian noninstitutionalized United States population. The stages of sample selection are: (1) selection of Primary Sampling Units (PSUs) which are counties or small groups of contiguous counties, (2) segments within PSUs (a block or group of blocks containing a cluster of households), (3) households within segments, and (4) one or more participants within households. A total of 15 PSUs are visited during a 12-month time period. Details of the design and content of each survey are available at the NHANES Web site.

Weight:  

Most data analyses require either the interviewed sample weight (variable name: WTINT2YR) or examined sample weight (variable name: WTMEC2YR). Use of the correct sample weight for NHANES analyses is extremely important. A good rule of thumb is to use "the least common denominator" approach. With this approach, the analyst checks the variables of interest. The variable that was collected on the smallest number of persons is the least common denominator, and the sample weight that applies to that variable is the appropriate one to use for that particular analysis.

NCHS June 2004 Version--NHANES Analytic Guidelines

Beginning in 1999, the National Health and Nutrition Examination Survey (NHANES) became a continuous, annual survey rather than the periodic survey that it had been in the past. For a variety of reasons, including disclosure and reliability issues, the survey data are released on public use data files every two years. Thus, the data release cycle for the ongoing (and continuous) NHANES is described as NHANES 1999-2000, NHANES 2001-2002, NHANES 2003-2004, etc. In addition to the analysis of data from any two-year cycle, it is possible to combine two or more "cycles" (e.g., 1999-2000 and 2001-2002) to create NHANES 1999-2002, thus increasing sample size and analytic options. In order to produce estimates with greater statistical reliability, combining two or more two-year cycles of the continuous NHANES is encouraged and strongly recommended. To facilitate analysis of these first two cycles of the continuous NHANES, the appropriate four-year sample weights have been calculated and added to the demographic data files for both 1999-2000 and 2001-2002. Thus, users of the earlier release of the NHANES 1999-2000 demographic file must use the updated demographic file to appropriately analyze the combined four-year data. These four-year sample weights have the same variable name in each two-year demographic file. For example, for the sample persons for whom there are MEC data items, the variable name for the four year weight is WTMEC4YR. The procedure for variance estimation (sampling errors) has been changed for NHANES 1999-2000 to one that protects confidentiality and allows the use of "PSUs" and is the recommended approach for analysis on the ongoing and continuous NHANES. This method creates Masked Variance Units (MVUs) which can be used as if they were Pseudo PSUs to estimate sampling errors (similar to past NHANES). The Pseudo-PSUs on the data file are not the "true" design PSUs. They are a collection of secondary sampling units aggregated into groups called Masked Variance Units (MVUs) for the purpose of variance estimation. They produce variance estimates that closely approximate the variances that would have been estimated using the "true" design variance estimates. These MVUs have been created for both NHANES 1999-2000 and NHANES 2001-2002 and added to the demographic data files for both two-year periods. They can also be used for the combined four-year dataset. The stratum variable is SDMVSTRA and the PSU variable is SDMVPSU. Software such as SUDAAN, STATA, and SAS can be used to estimate sampling errors by the Taylor series (linearization) method. Typically, the dataset should first be sorted by SDMVSTRA and SDMVPSU. There are no replicate weights provided for NHANES 2001-2002. Replication techniques can still be used to estimate sampling errors if the software, such as WESVAR, computes its own set of replicate weights based on the nested PSU within stratum design. Some data components of NHANES are only available for 1999-2000 or 2001-2002. For these components, the two-year sample weights and the two-year MVUs can be used for analysis. For 2001-2002, the two-year weights and MVUs are provided on the demographic data file. For 1999-2000, the previously released demographic file has been updated to add the MVUs and four-year sample weights. At this time, the preferred approach for calculating sampling errors is to use the MVUs and to ignore the JK-1 technique utilized as an interim approach with the release of the NHANES 1999-2000 data. On occasion, there may be a particular issue that requires comparison of results from NHANES 1999-2000 with NHANES 2001-2002. For summary statistics such as means and proportions, the appropriate two-year sample weights and MVUs can be used for reasonably valid inferences (although caution should be used when producing estimates for any detailed population subgroup). Calculation of totals (e.g., estimates of the number of persons with a particular characteristic such as BMI greater than 30 or with impaired glucose tolerance) is not appropriate for NHANES 1999-2000 unless the numbers are ratio-adjusted to population counts based on year 2000 Census figures. This is not an issue for NHANES 2001-2002 which was linked to the 2000 Census counts. Users are encouraged to check the NHANES Web site on a regular basis to be aware of the latest version of these NHANES analytic guidelines.

Mode of Data Collection:   audio computer-assisted self interview (ACASI), computer-assisted personal interview (CAPI), computer-assisted self interview (CASI), face-to-face interview, on-site questionnaire

Presence of Common Scales:   DISC -- Predictive Scale

Extent of Processing:  ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major statistical software formats as well as standard codebooks to accompany the data. In addition to these procedures, ICPSR performed the following processing steps for this data collection:

  • Performed consistency checks.
  • Created variable labels and/or value labels.
  • Created online analysis version with question text.
  • Checked for undocumented or out-of-range codes.

Version(s)

Original ICPSR Release:  

Version History:

  • 2012-02-22 Data and documentation for the following parts have been updated: 137. Additional updates will occur in the future as the NCHS revises the NHANES data collection frequently.
  • 2011-09-19 The missing value designations for this study have been updated to be consistent with the other NHANES studies (ICPSR 25502, 25503, 25504, 25505). Additionally, the data for Part 228 have been updated to reflect the most recent documentation provided by the NCHS.
  • 2011-05-03 The majority of the data files in this collection were merged with the demographics file.

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