Key Concepts About Identifying NHANES II Variable Names and File Locations

Variables are stored in different data files as described in the NHANES II Data Structure & Contents module. All NHANES II data files contain demographic and sample weight variables. Data files are organized by their collection method and questionnaire. For example, blood pressure measurements are in the Physician's Examination file, serum cholesterol variables are in the Hematology and Biochemistry file, and questions about previous diagnosis of hypertension or taking medications for hypertension are in the Medical History Questionnaire file. All these variables would be required in a complete analysis of cardiovascular disease.

Your analysis will require a subset of the variables available in NHANES II. To decide which variables are needed in your analysis, you need to review the survey documentation. In addition to data files most component files have:

The documentation file provides a description of the survey and the specific component, an index listing each data item, and special notes or appendices in the overall component or data item. The SAS code file contains SAS code that may be used to input and label data items. The Formatted SAS code file contains SAS code that may be used to input, label, and format data items.

Tape documentation PDF files contain several useful sections: an index section listing variables and tape position, a section with a variable description, tape position, variable code values and frequency counts, and a section with special notes on collection and editing procedures and other notes that should be considered in analysis. Use the search feature to speed up your search for variables relevant to your analysis. Not every result returned will be relevant to your analysis. Use the index list at the beginning of each tape documentation PDF file to identify the variable descriptions.

All variables listed in the tape documentation PDF files have been publicly released and are available for download in the associated data file. If you wish to use a variable that is not listed in any of the tape documentation files, you will need to use the Research Data Center. You can review the Research Data Center for more information about how to obtain access to non-publicly released variables.


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