Key Concepts About NHANES III Data Structure


NHANES III was conducted in two phases, from 1988-91 and from 1992-94.  Most analyses are conducted on the combined 6-year data files from 1988-94. 


Data Releases

NHANES III data were released in separate intervals.  Two specific releases contain the majority of data of interest to most researchers – these are Series 11, nos. 1a and 2a.  There are a number of other data releases (e.g. series 3a through 25a) which contain additional data based upon a subsample of the survey, very specific topic areas which were delayed in their original release, or data files based on surplus sera projects (so data releases based on NHANES III continue to occur).

Series 11 no. 1a contains the majority of the data and corresponding documentation for the survey interview and examination components.  These are found in five separate data files: the NHANES III Household Adult Data File, NHANES III Household Youth Data File, NHANES III Examination Data File, NHANES III Laboratory Data File, and the NHANES III Dietary Recall Data Files.

Series 11 no. 2a contains data not available for the Series 11 no. 1a release in July 1997. The data in this release includes electrocardiogram, dietary recall, laboratory, and vitamin/supplements/prescription drug data.


Data Files

Several of the files in Series 11 no. 1a are very large.  However, variables tend to be grouped as they were in the questionnaires and the user would be well advised to use the search feature to find the variables of interest to them.  Care should be taken to search both the household and the examination files, as some items of interest, such as blood pressure measurements, were ascertained in both.

In the picture below, click the headings to see examples of the types of data to be found in the various data files constituting the NHANES III data releases.


Examples of NHANES III - Series 11 Data Files and Variables

(Printer-friendly version of this interactive animation also available.)


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