The Third National Health and Nutrition Examination Survey, (NHANES III), 1988-94 on CD-ROM (Series 11, No. 3A) The National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) collects, analyzes, and disseminates data on the health status of U.S. residents. The results of surveys, analyses, and studies are made known through a number of data release mechanisms including publications, mainframe computer data files, CD-ROMs (Search and Retrieval Software, Statistical Export and Tabulation System (SETS)), and the Internet. The National Health and Nutrition Examination Survey (NHANES) is a periodic survey conducted by NCHS. The third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988 through 1994, was the seventh in a series of these surveys based on a complex, multi-stage sample plan. It was designed to provide national estimates of the health and nutritional status of the United States' civilian, noninstitutionalized population aged two months and older. This release, Series 11 No. 3A, contains data obtained from a second exam of selected survey participants, who had a primary exam. This release does not replace the previous NHANES III data releases (Series 11, Nos. 1A and 2A). The following table summarizes the NHANES III data which are currently available on CD-ROM. Table 1. Available NHANES III CD-ROMs +----------------------+-------+---------+------------------------------------+ |CD-ROM Name |Release|Size in |Data Files / Description | | |Date |Megabytes| | +----------------------+-------+---------+------------------------------------+ |NHANES III, 1988-94, |July | 33 |Second exam sample files for | |Series 11, No. 3A, |1999 | |dietary recall, examination, | |ASCII Version (this | | |laboratory, additional laboratory | |release) | | |analytes and documentation | +----------------------+-------+---------+------------------------------------+ |NHANES III, 1988-94, |April | 407 |Dietary recall (replacement), | |Series 11, No. 2A, |1998 | |electrocardiography, laboratory | |ASCII Version | | |(additional analytes), and | | | | |vitamins/medicines data files and | | | | |documentation | +----------------------+-------+---------+------------------------------------+ |NHANES III, 1988-94, |October| 285 |Adult and youth household | |Series 11, No. 1, |1997 | |questionnaire, examination, and | |Revised SETS Version | | |laboratory data files and | |1.22a | | |documentation, plan and operation, | | | | |analytic and reporting guidelines, | | | | |weighting and estimation | | | | |methodology, field operations, | | | | |non-response bias | +----------------------+-------+---------+------------------------------------+ |NHANES III, 1988-94, |July | 454 |Adult and youth household | |Series 11, No. 1A, |1997 | |questionnaire, dietary recall, | |ASCII Version | | |examination, and laboratory data | | | | |files and documentation | +----------------------+-------+---------+------------------------------------+ |NHANES III, 1988-94, |July | 285 |Adult and youth household | |Series 11, No. 1, |1997 | |questionnaire, examination, and | |SETS Version 1.22a * | | |laboratory data files and | | | | |documentation | +----------------------+-------+---------+------------------------------------+ |NHANES III Reference |October| 152 |Plan and operation, analytic and | |Manuals and Reports |1996 | |reporting guidelines, weighting and | |October 1996 | | |estimation methodology, field | | | | |operations, non-response bias | +----------------------+-------+---------+------------------------------------+ * Do not use this CD-ROM. It had technical problems and has been superseded by the revised SETS version 1.22a, Series 11, No. 1, released in October 1997. This release, Series 11, No. 3A, contains previously unreleased data and corrections. There are seven files in this release: CFFSE, EXAMDRSE, EXAMSE, IFFSE, LABSE and LAB2SE AND VIFSE. For each of these files there is a corresponding documentation file (with extension .DOC) in ASCII text format, and a corresponding SAS code file (with extension .SAS) to create a SAS data set from the ASCII file. The first release of NHANES III data is available on three different CD-ROMs. The first CD-ROM, Series 11, No. 1 SETS Version 1.22a contains data accessible through the Statistical Export and Tabulation System (SETS) retrieval software as well as documentation. This CD-ROM had technical problems and should not be used; it has been superseded by the Series 11, No. 1 Revised SETS Version 1.22a. This revised CD-ROM includes corrections to the SETS software and also contains the NHANES III Reference Manuals and Reports. A third CD-ROM, Series 11, No. 1A, contains the same data and documentation (except the Reference Manuals and Reports) as on the Series 11, No. 1 Revised Sets Version 1.22a CD-ROM plus the expanded dietary recall data and documentation. All data on the Series 11, No. 1A CD-ROM are in ASCII format only. The second NHANES III data release, CD-ROM series 11 No. 2A. Series 11 No. 2A contains a replacement for dietary recall and previously unreleased vitamins/medicines data; additional laboratory analysts; and electrocardiography data. Additionally electrocardiography data from NHANES I and II was included. Background information on the procedures, survey components, questionnaires, examination and laboratory methods, and statistical analysis guidelines is available on the NHANES III Reference Manuals and Reports (CD-ROM) and on the Series 11, No. 1 Revised SETS Version 1.22a CD-ROM. All data users are strongly encouraged to review these reference materials and reports before analyzing NHANES III data. Guidelines for Data Users o NHANES III survey design and demographic variables are found on the Household Adult Data File, Household Youth Data File, the Laboratory Data File and the Examination Data File. In preparing a data set for analysis, other data files should be merged with either or both of the Adult Household Data File or the Youth Household Data File to obtain many important analytic variables. o All of the NHANES III public use data files are linked with the common survey participant identification number (SEQN). Merging information from multiple NHANES III data files using this variable ensures that the appropriate information for each survey participant is linked correctly. o NHANES III public use data files do not have the same number of records on each file. The Household Questionnaire Files (divided into two files, Adult and Youth) contain more records than the Examination Data File because not everyone who was interviewed completed the examination. The Laboratory Data File contains data only for persons aged one year and older. The Individual Foods Data File based on the dietary recall, the Prescription Medication Data File, and The Vitamin and Minerals Data File all have multiple records for each person rather than the one record per sample person contained in the other data files. o For each data file, SAS program code with standard variable names and labels is provided as separate text files on the CD-ROM that contains the data files. This SAS program code can be used to create a SAS data set from the data file. o Modifications were made to items in the questionnaires, laboratory, and examination components over the course of the survey; as a result, data may not be available for certain variables for the full six years. In addition, variables may differ by phase since some changes were implemented between phases. Users are encouraged to read the Notes sections of the file documentation carefully for information about changes. o Extremely high and low values have been verified whenever possible, and numerous consistency checks have been performed. Nonetheless, users should examine the range and frequency of values before analyzing data. o Some data were not ready for release at the time of this publication due to continued processing of the data or analysis of laboratory specimens. A listing of those data are available in the general information section of each data file. o Confidential and administrative data are not available or released to the public. Additionally, some variables have been recoded to protect the confidentiality of the survey participants. For example, all age-related variables were recoded to 90+ years for persons who were 90 years of age or older. o Some variable names may differ from those used in the Phase 1 NHANES III Provisional Data Release and some variables included in the Phase 1 provisional release may not appear on these files. Do not use the Phase 1 provisional release; use the current (six-year) release. o Although the data files have been edited carefully, it is possible that errors may still exist. Please notify NCHS staff (301-458-4636) of any suspected errors in the data file or the documentation. Refer to the NCHS website at www.cdc.gov/nchswww/ for updates to these data files. Analytic Considerations o NHANES III (1988-94) was designed so that the survey's first three years, 1988-91, its last three years, 1991-94, and the entire six years were national probability samples. Analysts are encouraged to use all six years of survey results. o Sample weights are available for analyzing NHANES III data. One of the following three sample weights will be appropriate for nearly all analyses: interviewed sample final weight (WTPFQX6), examined sample final weight (WTPFEX6), and mobile examination center (MEC)- and home-examined sample final weight (WTPFHX6). Choosing which of these sample weights to use in any analysis depends on the variables being used. A good rule of thumb is to use "the least common denominator" approach. In this approach, the user 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 analysis. For more detailed information, see the Analytic and Reporting Guidelines for NHANES III (U.S. DHHS, 1996). Referencing or Citing NHANES III Data o In publications, please acknowledge NCHS as the original data source. For instance, the reference for the NHANES III Examination Data File on this CD-ROM is: U.S. Department of Health and Human Services (DHHS). National Center for Health Statistics. Third National Health and Nutrition Examination Survey, 1988-1994, NHANES III Second Examination Data File (CD-ROM Series 11, No. 3A). Hyattsville, MD: Centers for Disease Control and Prevention, 1999. Using the files on this CD-ROM Your analysis software should be able to read data files directly from this CD-ROM. You may also copy any data file from this CD-ROM to your hard drive using the file manager (Windows 95) or the "copy" command at the DOS prompt. Please note that some files are very large (one data file exceeds 300 megabytes). Check the file sizes before copying. To access a documentation file open it in a word processor, set the margins to zero and the font to Courier 12 point. View or print any pages needed. Some of these documents are hundreds of pages long. For SAS users, open the SAS program for the data set required into Program Manager. Change the FILENAME statement as needed for the operating system (the supplied FILENAME assumes DOS conventions where the CD-ROM drive is D:). To create a permanent SAS data set change the DATA statement. If space is limited, consider adding a KEEP statement to specify the variables of interest. The data files may be used in other analysis packages by using the field positions found in the index portion of the corresponding documentation. Problems Using the Data NHANES III is a wonderfully rich source of data and NCHS encourages you to use the data for research and analysis. However, the dataset is large and complex and familiarity with data file manipulation and analysis is required. NCHS does not have the personnel resources to perform analyses, check results, debug programs or do literature review for your work. Thorough review of the extensive documentation on the planning of the survey, analytic guidelines and individual datasets should resolve most questions. If you still have questions after careful review of the documentation, please contact the Data Dissemination Branch at (301) 458-4636.