DOI: 10.3886/icpsr25503.v7
title: National Health and Nutrition Examination Survey (NHANES), 2003-2004
title: Version 7

description: 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. 
 For NHANES 2003-2004, there were 12,761 persons selected for the sample, 10,122 of those were interviewed (79.3 percent) and 9,643 (75.6 percent) were examined in the mobile examination centers (MEC). Many of the NHANES 2003-2004 questions were also asked in NHANES II 1976-1980, Hispanic HANES 1982-1984, NHANES III 1988-1994, and NHANES 1999-2002. New questions were added to the survey based on recommendations from survey collaborators, NCHS staff, and other interagency work groups. As in past health examination surveys, data were collected on the prevalence of chronic conditions in the population. Estimates for previously undiagnosed conditions, as well as those known to and reported by survey respondents, are produced through the survey. 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 diseases, medical conditions, and health indicators that were studied include: anemia, cardiovascular disease, diabetes and lower extremity disease, environmental exposures, equilibrium, hearing loss, infectious diseases and immunization, kidney disease, mental health and cognitive functioning, nutrition, obesity, oral health, osteoporosis, physical fitness and physical functioning, reproductive history and sexual behavior, respiratory disease (asthma, chronic bronchitis, emphysema), sexually transmitted diseases, skin diseases, and vision. The sample for the survey was selected to represent the United States population of all ages. Special emphasis in the 2003-2004 NHANES was on adolescent health and the health of older Americans. To produce reliable statistics for these groups, adolescents aged 15-19 years and persons aged 60 years and older were over-sampled for the survey. African Americans and Mexican Americans were also over-sampled to enable accurate estimates for these groups. Several important areas in adolescent health, including nutrition and fitness and other aspects of growth and development, were addressed. Since the United States has experienced dramatic growth in the number of older people during the twentieth century, the aging population has major implications for health care needs, public policy, and research priorities. NCHS is working with public health agencies to increase the knowledge of the health status of older Americans. NHANES has a primary role in this endeavor. In the examination, all participants visit the physician who takes their pulse or blood pressure. Dietary interviews and body measurements are included for everyone. All but the very young have a blood sample taken and see the dentist. Depending upon the age of the participant, the rest of the examination includes tests and procedures to assess the various aspects of health listed above. Usually, the older the individual, the more extensive the examination. Some persons who are unable or unwilling to come to the examination center may be given a less extensive examination in their homes. 
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 2003-2004 data). (2) Recoded Demographic Variables: these variables include age (age in months for persons through age 19 years, 11 months; age in years for 1- to 84-year-olds, and a top-coded age group of 85 years of age and older), gender, a race/ethnicity variable, current or highest grade of education completed, (less than high school, high school, and more than high school education), country of birth (United States, Mexico, or other foreign born), Poverty Income Ratio (PIR), income, and a pregnancy status variable (adjudicated from various pregnancy related variables). Some of the groupings were made due to limited sample sizes for the two-year data set. (3) Interview and Examination Sample Weight Variables: sample weights are available for analyzing NHANES 2003-2004 data. For a complete listing of survey contents for all years of the NHANES see the document -- Survey Content -- NHANES 1999-2010.
description: The most recent series of data collection waves for 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 2003-2004 includes over-sampling of low-income persons, adolescents 12-19 years of age, persons 60 years of age and older, 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.
<strong>Target Populations</strong>
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 older, and senior meal program participation questions were asked of respondents 60 years of age and older. Data users should review the survey questionnaire codebooks thoroughly to determine the target populations for each NHANES questionnaire section and sub-section.
<strong>The NHANES Health Examination Component</strong>
When a participant arrives at the MEC, the MEC Coordinator greets the participant and verifies all pertinent identifier information. Each participant receives a disposable paper gown and a pair of slippers to wear during their examination. Persons six years of age and older are asked to provide a urine specimen. MEC staff direct participants to the rooms where the examination components are conducted. In addition to the MEC Coordinator, 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. Upon completion of the examination, each examinee is remunerated. Some of the medical findings from 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.
<strong>MEC Operations</strong>
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.
<strong>Home Examinations</strong>
Participants who are 50 years and older or less than 1 year old and are unable or unwilling to travel to the MEC were offered a home examination administered by an examiner from the MEC.
description: Sample weights are available for analyzing NHANES 2003-2004 data. Most data analyses require either the interviewed sample weight (variable name: WTINT2YR) or examined sample weight (variable name: WTMEC2YR). The two-year sample weights (WTINT2YR, WTMEC2YR) should be used for NHANES 2003-2004 analyses. Use of the correct sample weight for NHANES analyses is extremely important and depends on the variables being used. 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. Please refer to the NHANES 2003-2004 Analytic Guidelines provided with the data release files to determine the appropriate analytic methodology.
<strong>NCHS September 2006 Version--NHANES Analytic Guidelines</strong>
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., 2003-2004 and 2005-2006) to create NHANES 2003-2006, 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. When combining cycles of data, it is extremely important that (1) the user verify that data items collected in all combined years were comparable in wording and methods and (2) use a proper sampling weight. Beginning in 2003, the survey content for each two year period is held as constant as possible to be consistent with the data release cycle. In the first four years of the continuous survey, this was not always the case, and some special data release and data access procedures had to be developed and used for selected survey content collected in "other than two-year" intervals (see the NHANES release policy). The decision on how many years of NHANES data are required for a particular analysis can be summarized by the concept of minimum sample size required. The minimum sample size is determined by the statistic to be estimated (e.g. mean, total, proportion...), the reliability criteria (e.g. 20 or 30 percent relative standard error), the Design Effect for the statistics (DEFF defined as the variance inflation factor), and the degrees of freedom for the standard error estimate. Earlier NHANES surveys were conducted for four or more years and, thus, have larger samples than a two-year cycle of the current continuous NHANES. However, in each of those surveys, many sub-domains did not meet minimum sample size requirements and in those cases the above concerns were (and still are) relevant. When combining two or more two-year cycles of the continuous NHANES, the user should use the following procedure for calculating the appropriate combined sample weights. When combining two or more two-year cycles of the continuous NHANES, the user must calculate new sample weights before beginning any analysis of the data. NCHS will not be calculating and including all possible combinations of multiple two-year cycles of the continuous survey because it would be impractical to produce them and include them on all public release files. Because of a particular issue with Census population estimates, a set of four-year weights was created for the first four years of the continuous NHANES -- 1999-2002. The sample weights for NHANES 1999-2000 were based on population estimates developed by the Bureau of the Census before the Year 2000 Decennial Census counts became available. The two-year sample weights for NHANES 2001-2002 were based on population estimates that incorporate the year 2000 Census counts. The two population estimates were not strictly comparable. To facilitate analysis for these first four years of the continuous NHANES, appropriate four-year sample weights (comparable to Census 2000 counts) were calculated and added to the demographic data files for both 1999-2000 and 2001-2002. These sample weights have the same variable name in each file. For example, for the sample persons for whom there are MEC data items, the variable name for the four-year weight is WTMEC4YR. 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 1999-2002. Because NHANES 2003-2004 uses the same year 2000 Census counts as were used for NHANES 2001-2002, there is no need to create special four-year weights for 2001-2004. For a
four-year estimate for 2001-2004, one can create a new variable for a four-year weight by assigning half of the two-year weight for 2001-2002 if the person was sampled in 2001-2002 or assigning half of the two-year weight for 2003-2004 if the person was sampled in 2003-2004. This is possible because the two-year weights for 2003-2004 are comparable to the 2001-2002 weights (in terms of a population basis). For an estimate for the six years 1999-2004, a six-year weight variable can be created by assigning two-thirds of the four-year weight for 1999-2002 if the person was sampled in 1999-2002, or assigning one-third of the two-year weight for 2003-2004 if the person was sampled in 2003-2004. This is possible because the 2003-2004 weights are also comparable (on a population basis) to the combined four-year weights specifically created for 1999-2002.
This information summarizes the most recent analytic and reporting guidelines that should be used for most NHANES analyses and publications. It is important for users to understand the entire document and to become familiar with statistical issues in the analysis of complex survey data. These suggested guidelines provide a framework to users for producing estimates that conform to the analytic design of the survey. Because statistical methods for analyzing complex survey data are continually evolving, these recommendations may differ slightly from those used by analysts for previous NHANES surveys. It is important to remember that the statistical guidelines in this document are not absolute. When conducting analyses, the analyst needs to use his/her subject matter knowledge (including methodological issues), as well as information about the survey design. The more one deviates from the original analytic categories and original analytic objectives defined in the planning documents, the more important it is to evaluate the results carefully and to interpret the findings cautiously. Future versions of the NHANES Analytic and Reporting Guidelines will include additional topics, such as sample sizes and response rates for each NHANES survey, hypothesis testing, multivariate analysis, and a discussion of the concept of statistical versus practical significance. These are Guidelines not standards. Depending upon the subject matter and statistical efficiency, specific analyses may depart from these guidelines; but the burden of proof for statistical efficiency and for appropriate data interpretation is on the data user/analyst. Again, NHANES data files from the continuous survey are publicly released on a two-year basis (1999-2000, 2001-2002, 2003-2004, etc.) and as small, content specific files. The data files and associated documentations, as well as these analytic guidelines, may be edited and/or updated to reflect new data release files.
Users should periodically check the NHANES website to determine if any new or revised data files have been released and if these analytic guidelines have been updated.
description: Presence of Common Scales: DISC -- Predictive Scale
description: 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.
description: Datasets: 
DS0: Study-Level Files
DS1: Demographics
DS11: Examination: Audiometry (Subsample)
DS12: Examination: Audiometry Tympanometry
DS13: Examination: Balance
DS14: Examination: Bioelectrical Impedance
DS15: Examination: Blood Pressure
DS16: Examination: Body Measurements
DS17: Examination: Cardiovascular Fitness
DS18: Examination: Composite International Diagnostic Interview (Generalized Anxiety Disorder) (Subsample)
DS19: Examination: Composite International Diagnostic Interview (Major Depression Module) (Subsample)
DS20: Examination: Composite International Diagnostic Interview (Panic Disorder Module) (Subsample)
DS21: Examination: Dermatology
DS22: Examination: Dietary Interview (Individual Foods File -- First Day)
DS23: Examination: Dietary Interview (Individual Foods File -- Second Day)
DS24: Examination: Dietary Interview (Total Nutrient Intakes -- First Day)
DS25: Examination: Dietary Interview (Total Nutrient Intakes -- Second Day)
DS26: Examination: Dual Energy X-Ray Absorptiometry (DXX)
DS27: Examination: Dual Energy X-Ray Absorptiometry Supplemental (DXX_S)
DS28: Examination: Food Frequency Questionnaire -- Raw Questionnaire Responses
DS29: Examination: Food Frequency Questionnaire -- DietCalc Output
DS30: Examination: Lower Extremity Ankle Brachial Blood Pressure Index
DS31: Examination: Lower Extremity Disease (Peripheral Neuropathy)
DS32: Examination: Oral Health (Addendum)
DS33: Examination: Oral Health (Dentition)
DS34: Examination: Oral Health (Lower Periodontal)
DS35: Examination: Oral Health (Upper Periodontal)
DS36: Examination: Oral Health (Recommendation of Care/Referral)
DS37: Examination: Physical Activity Monitor
DS38: Examination: Vision Exam
DS101: Laboratory: Antibody to Coxiella Burnetii (Q-Fever) (Surplus Sera)
DS102: Laboratory: Antibody to Cytomegalovirus IgG (Surplus Sera)
DS103: Laboratory: Antibody to Mumps (Surplus Sera)
DS104: Laboratory: Melamine (Surplus Urine)
DS105: Laboratory: Varicella-Zoster Virus Antibody (Surplus Sera)
DS106: Laboratory: Lab 02 Hepatitis
DS107: Laboratory: Lab 02 Hepatitis B Surface Antibody
DS108: Laboratory: Lab 02 Hepatitis A Antibody
DS109: Laboratory: Lab 03 Human Immunodeficiency Virus
DS110: Laboratory: Lab 04 Urinary Perchlorate
DS111: Laboratory: Lab 04 Volatile Organic Compounds In Blood And Water
DS112: Laboratory: Lab 05 Chlamydia Trachomatis And Neisseria Gonorrhea
DS113: Laboratory: Lab 06 Acrylamide And Glycidamide
DS114: Laboratory: Lab 06 Blood Lead, Cadmium And Mercury
DS115: Laboratory: Lab 06 Methylmalonic Acid And Homocysteine
DS116: Laboratory: Lab 06 Rbc Folate, Serum Folate, And Vitamin B12
DS117: Laboratory: Lab 06 Serum Cotinine
DS118: Laboratory: Lab 06 Ferritin And Transferrin Receptor
DS119: Laboratory: Lab 06 Heavy Metals
DS120: Laboratory: Lab 06 Urinary Iodine
DS121: Laboratory: Lab 06 Urinary Phytoestrogens
DS122: Laboratory: Lab 06 Urinary Total Arsenic And Speciated Arsenics
DS123: Laboratory: Lab 06 Urinary Mercury
DS124: Laboratory: Lab 06 Vitamin C
DS125: Laboratory: Lab 06 Vitamin D
DS126: Laboratory: Lab 09 Herpes I And Herpes II
DS127: Laboratory: Lab 10 Glycohemoglobin
DS128: Laboratory: Lab 10AM Glucose, C-Peptide, Insulin
DS129: Laboratory: Lab 11 CRP
DS130: Laboratory: Lab 11 PSA
DS131: Laboratory: Lab 13 Total Cholesterol And HDL Cholesterol
DS132: Laboratory: Lab 13AM Triglycerides And LDL Cholesterol
DS133: Laboratory: Lab 16 Urinary Albumin
DS134: Laboratory: Lab 17 Toxoplasma (IgG and IgM)
DS135: Laboratory: Lab 19 Measles Rubella And Varicella
DS136: Laboratory: Lab 20 Lead Dust
DS137: Laboratory: Lab 24 Environmental Pesticides
DS138: Laboratory: Lab 24 Environmental Phenols
DS139: Laboratory: Lab 24 Polyfluorinated Compounds
DS140: Laboratory: Lab 24 Urinary Phthalates
DS141: Laboratory: Lab 25 Complete Blood Count
DS142: Laboratory: Lab 26 Urinary Current Use Pesticide
DS143: Laboratory: Lab 26 Urinary Organophosphate Insecticides
DS144: Laboratory: Lab 28 Dioxins, Furans, and Coplanar PCBS
DS145: Laboratory: Lab 28 Non-Dioxin-Like Polychlorinated Biphenyls
DS146: Laboratory: Lab 28 Organochlorine Pesticides
DS147: Laboratory: Lab 28 Polybrominated Diphenyl Ethers
DS148: Laboratory: Lab 31 Polyaromatic Hydrocarbons
DS149: Laboratory: Lab 34 Trichomonos, Vaginalis And Bacterial Vaginosis
DS150: Laboratory: Lab 35 Methicillin Resistant Staphylococcus Aureus
DS151: Laboratory: Lab 36 Syphilis IgG, RR and TP-PA
DS152: Laboratory: Lab 37 Human Papillomavirus (HPV) DNA Hybrid Capture, PCR, and Hybridization Results from Vaginal Swab Samples
DS153: Laboratory: Lab 39 Erythrocyte Protoporphyrin And Selenium
DS154: Laboratory: Lab 40 Biochemistry Profile
DS155: Laboratory: Lab 40 Iron, TIBC and Transferrin
DS156: Laboratory: Lab 43 Vitamin B6
DS157: Laboratory: Lab 45 Vitamin A, E And Carotenoids
DS158: Laboratory: Lab 52 HPV Serum
DS159: Laboratory: Phlebotomy Fasting Questions
DS160: Laboratory: Urine Collection (Pregnancy)
DS201: Questionnaire: Acculturation
DS202: Questionnaire: Alcohol Use
DS203: Questionnaire: Analgesics Pain Relievers
DS204: Questionnaire: Audiometry
DS205: Questionnaire: Balance
DS206: Questionnaire: Blood Pressure
DS207: Questionnaire: Cardiovascular Disease And Health
DS208: Questionnaire: Current Health Status
DS209: Questionnaire: Dermatology
DS210: Questionnaire: Diabetes
DS211: Questionnaire: Diet Behavior And Nutrition
DS212: Questionnaire: Dietary Supplement Use - Supplement Counts
DS213: Questionnaire: Dietary Supplement Use - Participants Use Of Supplement
DS214: Questionnaire: Dietary Supplement Use - Supplement Information
DS215: Questionnaire: Dietary Supplement Use - Ingredient Information
DS216: Questionnaire: Dietary Supplement Use - Supplement Blend
DS217: Questionnaire: Drug Use
DS218: Questionnaire: Early Childhood
DS219: Questionnaire: Family Smoking
DS220: Questionnaire: Food Security
DS221: Questionnaire: Health Insurance
DS222: Questionnaire: Hepatitis C Follow Up Questionnaire
DS223: Questionnaire: Hospital Utilization
DS224: Questionnaire: Housing Characteristics
DS225: Questionnaire: Immunization
DS226: Questionnaire: Kidney Conditions - Urology
DS227: Questionnaire: Medical Conditions
DS228: Questionnaire: Miscellaneous Pain
DS229: Questionnaire: Occupation
DS230: Questionnaire: Oral Health
DS231: Questionnaire: Osteoporosis
DS232: Questionnaire: Pesticide Use
DS233: Questionnaire: Physical Activity
DS234: Questionnaire: Physical Activity Individual Activities File
DS235: Questionnaire: Physical Functioning
DS236: Questionnaire: Prescription Medications
DS237: Questionnaire: Drug Information
DS238: Questionnaire: Prostate Conditions
DS239: Questionnaire: Prostate Specific Antigen Follow Up Questionnaire
DS240: Questionnaire: Reproductive Health
DS241: Questionnaire: Respiratory Health And Disease
DS242: Questionnaire: Smoking And Tobacco Use
DS243: Questionnaire: Smoking And Tobacco Use (MEC)
DS244: Questionnaire: Social Support
DS245: Questionnaire: Sexual Behavior
DS246: Questionnaire: Vision
DS247: Questionnaire: Weight History
description: The NHANES target population is the civilian, noninstitutionalized United States population.
description: audio computer-assisted self interview (ACASI); computer-assisted personal interview (CAPI); computer-assisted self interview (CASI); face-to-face interview; on-site questionnaireNCHS 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 documentation files are included with this ICPSR release and may be found at the
NHANES 2003-2004 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 2003-2004 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 2003-2004 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 2003-2004 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 2003-2004 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 2003-2004 data.Per agreement with NCHS, ICPSR distributes the data file(s) and text of the technical documentation for this collection as prepared by NCHS.IMPORTANT NOTE CONCERNING THE AVAILABILITY OF DATA FILES:
Dataset 37 is so large that it exceeds the software limitations for the Stata data file format (file extension .dta) and SAS Cport Transport file format (file extension .stc). As such, these files are not available. Users requiring these files are encouraged to utilize the ASCII version of the data file, along with the appropriate setup file for the desired software package. However, the setup file may need to be edited so that only a subset of the data is accessed, in an effort to avoid exceeding the software limitations.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 33 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 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.The old .tsv and .txt files have been taken down.